[PATCH 0/9] Suspend block api (version 5)

[PATCH 0/9] Suspend block api (version 5)

[Arve Hjønnevåg]

This patch series adds a suspend-block api that provides the same
functionality as the android wakelock api. The main change from
version 4 posted last week is that suspend blocking work has moved out
of the core workqueue code. The documentation has also been updated.

--
Arve Hjønnevåg <arve@android.com>

[PATCH 1/8] PM: Add suspend block api.

[Arve Hjønnevåg]

Adds /sys/power/policy that selects the behaviour of /sys/power/state.
After setting the policy to opportunistic, writes to /sys/power/state
become non-blocking requests that specify which suspend state to enter
when no suspend blockers are active. A special state, "on", stops the
process by activating the "main" suspend blocker.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 Documentation/power/opportunistic-suspend.txt |  114 +++++++++++
 include/linux/suspend_blocker.h               |   64 ++++++
 kernel/power/Kconfig                          |   16 ++
 kernel/power/Makefile                         |    1 +
 kernel/power/main.c                           |   89 ++++++++-
 kernel/power/power.h                          |    5 +
 kernel/power/suspend.c                        |    4 +-
 kernel/power/suspend_blocker.c                |  269 +++++++++++++++++++++++++
 8 files changed, 556 insertions(+), 6 deletions(-)
 create mode 100644 Documentation/power/opportunistic-suspend.txt
 create mode 100755 include/linux/suspend_blocker.h
 create mode 100644 kernel/power/suspend_blocker.c

diff --git a/Documentation/power/opportunistic-suspend.txt b/Documentation/power/opportunistic-suspend.txt
new file mode 100644
index 0000000..1a29d10
--- /dev/null
+++ b/Documentation/power/opportunistic-suspend.txt
@@ -0,0 +1,114 @@
+Opportunistic Suspend
+=====================
+
+Opportunistic suspend is a feature allowing the system to be suspended (ie. put
+into one of the available sleep states) automatically whenever it is regarded
+as idle.  The suspend blockers framework described below is used to determine
+when that happens.
+
+The /sys/power/policy sysfs attribute is used to switch the system between the
+opportunistic and "forced" suspend behavior, where in the latter case the
+system is only suspended if a specific value, corresponding to one of the
+available system sleep states, is written into /sys/power/state.  However, in
+the former, opportunistic, case the system is put into the sleep state
+corresponding to the value written to /sys/power/state whenever there are no
+active suspend blockers. The default policy is "forced". Also, suspend blockers
+do not affect sleep states entered from idle.
+
+When the policy is "opportunisic", there is a special value, "on", that can be
+written to /sys/power/state. This will block the automatic sleep request, as if
+a suspend blocker was used by a device driver. This way the opportunistic
+suspend may be blocked by user space whithout switching back to the "forced"
+mode.
+
+A suspend blocker is an object used to inform the PM subsystem when the system
+can or cannot be suspended in the "opportunistic" mode (the "forced" mode
+ignores suspend blockers).  To use it, a device driver creates a struct
+suspend_blocker that must be initialized with suspend_blocker_init(). Before
+freeing the suspend_blocker structure or its name, suspend_blocker_destroy()
+must be called on it.
+
+A suspend blocker is activated using suspend_block(), which prevents the PM
+subsystem from putting the system into the requested sleep state in the
+"opportunistic" mode until the suspend blocker is deactivated with
+suspend_unblock(). Multiple suspend blockers may be active simultaneously, and
+the system will not suspend as long as at least one of them is active.
+
+If opportunistic suspend is already in progress when suspend_block() is called,
+it will abort the suspend, unless suspend_ops->enter has already been
+executed. If suspend is aborted this way, the system is usually not fully
+operational at that point. The suspend callbacks of some drivers may still be
+running and it usually takes time to restore the system to the fully operational
+state.
+
+For example, in cell phones or other embedded systems, where powering the screen
+is a significant drain on the battery, suspend blockers can be used to allow
+user-space to decide whether a keystroke received while the system is suspended
+should cause the screen to be turned back on or allow the system to go back into
+suspend. Use set_irq_wake or a platform specific api to make sure the keypad
+interrupt wakes up the cpu. Once the keypad driver has resumed, the sequence of
+events can look like this:
+
+- The Keypad driver gets an interrupt. It then calls suspend_block on the
+  keypad-scan suspend_blocker and starts scanning the keypad matrix.
+- The keypad-scan code detects a key change and reports it to the input-event
+  driver.
+- The input-event driver sees the key change, enqueues an event, and calls
+  suspend_block on the input-event-queue suspend_blocker.
+- The keypad-scan code detects that no keys are held and calls suspend_unblock
+  on the keypad-scan suspend_blocker.
+- The user-space input-event thread returns from select/poll, calls
+  suspend_block on the process-input-events suspend_blocker and then calls read
+  on the input-event device.
+- The input-event driver dequeues the key-event and, since the queue is now
+  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
+- The user-space input-event thread returns from read. If it determines that
+  the key should leave the screen off, it calls suspend_unblock on the
+  process_input_events suspend_blocker and then calls select or poll. The
+  system will automatically suspend again, since now no suspend blockers are
+  active.
+
+                 Key pressed   Key released
+                     |             |
+keypad-scan          ++++++++++++++++++
+input-event-queue        +++          +++
+process-input-events       +++          +++
+
+
+Driver API
+==========
+
+A driver can use the suspend block api by adding a suspend_blocker variable to
+its state and calling suspend_blocker_init. For instance:
+struct state {
+	struct suspend_blocker suspend_blocker;
+}
+
+init() {
+	suspend_blocker_init(&state->suspend_blocker, "suspend-blocker-name");
+}
+
+Before freeing the memory, suspend_blocker_destroy must be called:
+
+uninit() {
+	suspend_blocker_destroy(&state->suspend_blocker);
+}
+
+When the driver determines that it needs to run (usually in an interrupt
+handler) it calls suspend_block:
+	suspend_block(&state->suspend_blocker);
+
+When it no longer needs to run it calls suspend_unblock:
+	suspend_unblock(&state->suspend_blocker);
+
+Calling suspend_block when the suspend blocker is active or suspend_unblock when
+it is not active has no effect (i.e., these functions don't nest). This allows
+drivers to update their state and call suspend suspend_block or suspend_unblock
+based on the result.
+For instance:
+
+if (list_empty(&state->pending_work))
+	suspend_unblock(&state->suspend_blocker);
+else
+	suspend_block(&state->suspend_blocker);
+
diff --git a/include/linux/suspend_blocker.h b/include/linux/suspend_blocker.h
new file mode 100755
index 0000000..f9928cc
--- /dev/null
+++ b/include/linux/suspend_blocker.h
@@ -0,0 +1,64 @@
+/* include/linux/suspend_blocker.h
+ *
+ * Copyright (C) 2007-2009 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _LINUX_SUSPEND_BLOCKER_H
+#define _LINUX_SUSPEND_BLOCKER_H
+
+#include <linux/list.h>
+
+/**
+ * struct suspend_blocker - the basic suspend_blocker structure
+ * @link:	List entry for active or inactive list.
+ * @flags:	Tracks initialized and active state.
+ * @name:	Name used for debugging.
+ *
+ * When a suspend_blocker is active it prevents the system from entering
+ * opportunistic suspend.
+ *
+ * The suspend_blocker structure must be initialized by suspend_blocker_init()
+ */
+
+struct suspend_blocker {
+#ifdef CONFIG_OPPORTUNISTIC_SUSPEND
+	struct list_head    link;
+	int                 flags;
+	const char         *name;
+#endif
+};
+
+#ifdef CONFIG_OPPORTUNISTIC_SUSPEND
+
+void suspend_blocker_init(struct suspend_blocker *blocker, const char *name);
+void suspend_blocker_destroy(struct suspend_blocker *blocker);
+void suspend_block(struct suspend_blocker *blocker);
+void suspend_unblock(struct suspend_blocker *blocker);
+bool suspend_blocker_is_active(struct suspend_blocker *blocker);
+bool suspend_is_blocked(void);
+
+#else
+
+static inline void suspend_blocker_init(struct suspend_blocker *blocker,
+					const char *name) {}
+static inline void suspend_blocker_destroy(struct suspend_blocker *blocker) {}
+static inline void suspend_block(struct suspend_blocker *blocker) {}
+static inline void suspend_unblock(struct suspend_blocker *blocker) {}
+static inline bool suspend_blocker_is_active(struct suspend_blocker *bl)
+								{ return 0; }
+static inline bool suspend_is_blocked(void) { return 0; }
+
+#endif
+
+#endif
+
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 5c36ea9..55a06a1 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -130,6 +130,22 @@ config SUSPEND_FREEZER
 
 	  Turning OFF this setting is NOT recommended! If in doubt, say Y.
 
+config OPPORTUNISTIC_SUSPEND
+	bool "Suspend blockers"
+	depends on PM_SLEEP
+	select RTC_LIB
+	default n
+	---help---
+	  Opportunistic sleep support.  Allows the system to be put into a sleep
+	  state opportunistically, if it doesn't do any useful work at the
+	  moment. The PM subsystem is switched into this mode of operation by
+	  writing "opportunistic" into /sys/power/policy, while writing
+	  "forced" to this file turns the opportunistic suspend feature off.
+	  In the "opportunistic" mode suspend blockers are used to determine
+	  when to suspend the system and the value written to /sys/power/state
+	  determines the sleep state the system will be put into when there are
+	  no active suspend blockers.
+
 config HIBERNATION_NVS
 	bool
 
diff --git a/kernel/power/Makefile b/kernel/power/Makefile
index 4319181..ee5276d 100644
--- a/kernel/power/Makefile
+++ b/kernel/power/Makefile
@@ -7,6 +7,7 @@ obj-$(CONFIG_PM)		+= main.o
 obj-$(CONFIG_PM_SLEEP)		+= console.o
 obj-$(CONFIG_FREEZER)		+= process.o
 obj-$(CONFIG_SUSPEND)		+= suspend.o
+obj-$(CONFIG_OPPORTUNISTIC_SUSPEND)	+= suspend_blocker.o
 obj-$(CONFIG_PM_TEST_SUSPEND)	+= suspend_test.o
 obj-$(CONFIG_HIBERNATION)	+= hibernate.o snapshot.o swap.o user.o
 obj-$(CONFIG_HIBERNATION_NVS)	+= hibernate_nvs.o
diff --git a/kernel/power/main.c b/kernel/power/main.c
index b58800b..5f0af6c 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -12,6 +12,7 @@
 #include <linux/string.h>
 #include <linux/resume-trace.h>
 #include <linux/workqueue.h>
+#include <linux/suspend_blocker.h>
 
 #include "power.h"
 
@@ -20,6 +21,27 @@ DEFINE_MUTEX(pm_mutex);
 unsigned int pm_flags;
 EXPORT_SYMBOL(pm_flags);
 
+struct policy {
+	const char *name;
+	bool (*valid_state)(suspend_state_t state);
+	int (*set_state)(suspend_state_t state);
+};
+static struct policy policies[] = {
+	{
+		.name		= "forced",
+		.valid_state	= valid_state,
+		.set_state	= enter_state,
+	},
+#ifdef CONFIG_OPPORTUNISTIC_SUSPEND
+	{
+		.name		= "opportunistic",
+		.valid_state	= request_suspend_valid_state,
+		.set_state	= request_suspend_state,
+	},
+#endif
+};
+static int policy;
+
 #ifdef CONFIG_PM_SLEEP
 
 /* Routines for PM-transition notifications */
@@ -146,6 +168,12 @@ struct kobject *power_kobj;
  *
  *	store() accepts one of those strings, translates it into the 
  *	proper enumerated value, and initiates a suspend transition.
+ *
+ *	If policy is set to opportunistic, store() does not block until the
+ *	system resumes, and it will try to re-enter the state until another
+ *	state is requested. Suspend blockers are respected and the requested
+ *	state will only be entered when no suspend blockers are active.
+ *	Write "on" to cancel.
  */
 static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
 			  char *buf)
@@ -155,12 +183,13 @@ static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
 	int i;
 
 	for (i = 0; i < PM_SUSPEND_MAX; i++) {
-		if (pm_states[i] && valid_state(i))
+		if (pm_states[i] && policies[policy].valid_state(i))
 			s += sprintf(s,"%s ", pm_states[i]);
 	}
 #endif
 #ifdef CONFIG_HIBERNATION
-	s += sprintf(s, "%s\n", "disk");
+	if (!policy)
+		s += sprintf(s, "%s\n", "disk");
 #else
 	if (s != buf)
 		/* convert the last space to a newline */
@@ -173,7 +202,7 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
 			   const char *buf, size_t n)
 {
 #ifdef CONFIG_SUSPEND
-	suspend_state_t state = PM_SUSPEND_STANDBY;
+	suspend_state_t state = PM_SUSPEND_ON;
 	const char * const *s;
 #endif
 	char *p;
@@ -184,7 +213,7 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
 	len = p ? p - buf : n;
 
 	/* First, check if we are requested to hibernate */
-	if (len == 4 && !strncmp(buf, "disk", len)) {
+	if (len == 4 && !strncmp(buf, "disk", len) && !policy) {
 		error = hibernate();
   goto Exit;
 	}
@@ -195,7 +224,7 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
 			break;
 	}
 	if (state < PM_SUSPEND_MAX && *s)
-		error = enter_state(state);
+		error = policies[policy].set_state(state);
 #endif
 
  Exit:
@@ -204,6 +233,55 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
 
 power_attr(state);
 
+/**
+ *	policy - set policy for state
+ */
+
+static ssize_t policy_show(struct kobject *kobj,
+			   struct kobj_attribute *attr, char *buf)
+{
+	char *s = buf;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(policies); i++) {
+		if (i == policy)
+			s += sprintf(s, "[%s] ", policies[i].name);
+		else
+			s += sprintf(s, "%s ", policies[i].name);
+	}
+	if (s != buf)
+		/* convert the last space to a newline */
+		*(s-1) = '\n';
+	return (s - buf);
+}
+
+static ssize_t policy_store(struct kobject *kobj,
+			    struct kobj_attribute *attr,
+			    const char *buf, size_t n)
+{
+	const char *s;
+	char *p;
+	int len;
+	int i;
+
+	p = memchr(buf, '\n', n);
+	len = p ? p - buf : n;
+
+	for (i = 0; i < ARRAY_SIZE(policies); i++) {
+		s = policies[i].name;
+		if (s && len == strlen(s) && !strncmp(buf, s, len)) {
+			mutex_lock(&pm_mutex);
+			policies[policy].set_state(PM_SUSPEND_ON);
+			policy = i;
+			mutex_unlock(&pm_mutex);
+			return n;
+		}
+	}
+	return -EINVAL;
+}
+
+power_attr(policy);
+
 #ifdef CONFIG_PM_TRACE
 int pm_trace_enabled;
 
@@ -231,6 +309,7 @@ power_attr(pm_trace);
 
 static struct attribute * g[] = {
 	&state_attr.attr,
+	&policy_attr.attr,
 #ifdef CONFIG_PM_TRACE
 	&pm_trace_attr.attr,
 #endif
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 46c5a26..9b468d7 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -236,3 +236,8 @@ static inline void suspend_thaw_processes(void)
 {
 }
 #endif
+
+/* kernel/power/suspend_block.c */
+extern int request_suspend_state(suspend_state_t state);
+extern bool request_suspend_valid_state(suspend_state_t state);
+
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 56e7dbb..dc42006 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -16,10 +16,12 @@
 #include <linux/cpu.h>
 #include <linux/syscalls.h>
 #include <linux/gfp.h>
+#include <linux/suspend_blocker.h>
 
 #include "power.h"
 
 const char *const pm_states[PM_SUSPEND_MAX] = {
+	[PM_SUSPEND_ON]		= "on",
 	[PM_SUSPEND_STANDBY]	= "standby",
 	[PM_SUSPEND_MEM]	= "mem",
 };
@@ -157,7 +159,7 @@ static int suspend_enter(suspend_state_t state)
 
 	error = sysdev_suspend(PMSG_SUSPEND);
 	if (!error) {
-		if (!suspend_test(TEST_CORE))
+		if (!suspend_is_blocked() && !suspend_test(TEST_CORE))
 			error = suspend_ops->enter(state);
 		sysdev_resume();
 	}
diff --git a/kernel/power/suspend_blocker.c b/kernel/power/suspend_blocker.c
new file mode 100644
index 0000000..9459361
--- /dev/null
+++ b/kernel/power/suspend_blocker.c
@@ -0,0 +1,269 @@
+/* kernel/power/suspend_blocker.c
+ *
+ * Copyright (C) 2005-2010 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/rtc.h>
+#include <linux/suspend.h>
+#include <linux/suspend_blocker.h>
+#include "power.h"
+
+enum {
+	DEBUG_EXIT_SUSPEND = 1U << 0,
+	DEBUG_WAKEUP = 1U << 1,
+	DEBUG_USER_STATE = 1U << 2,
+	DEBUG_SUSPEND = 1U << 3,
+	DEBUG_SUSPEND_BLOCKER = 1U << 4,
+};
+static int debug_mask = DEBUG_EXIT_SUSPEND | DEBUG_WAKEUP | DEBUG_USER_STATE;
+module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
+
+#define SB_INITIALIZED            (1U << 8)
+#define SB_ACTIVE                 (1U << 9)
+
+static DEFINE_SPINLOCK(list_lock);
+static DEFINE_SPINLOCK(state_lock);
+static LIST_HEAD(inactive_blockers);
+static LIST_HEAD(active_blockers);
+static int current_event_num;
+struct workqueue_struct *suspend_work_queue;
+struct suspend_blocker main_suspend_blocker;
+static suspend_state_t requested_suspend_state = PM_SUSPEND_MEM;
+static bool enable_suspend_blockers;
+
+#define pr_info_time(fmt, args...) \
+	do { \
+		struct timespec ts; \
+		struct rtc_time tm; \
+		getnstimeofday(&ts); \
+		rtc_time_to_tm(ts.tv_sec, &tm); \
+		pr_info(fmt "(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n" , \
+			args, \
+			tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, \
+			tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec); \
+	} while (0);
+
+static void print_active_blockers_locked(void)
+{
+	struct suspend_blocker *blocker;
+
+	list_for_each_entry(blocker, &active_blockers, link)
+		pr_info("active suspend blocker %s\n", blocker->name);
+}
+
+/**
+ * suspend_is_blocked() - Check if suspend should be blocked
+ *
+ * suspend_is_blocked can be used by generic power management code to abort
+ * suspend.
+ *
+ * To preserve backward compatibility suspend_is_blocked returns 0 unless it
+ * is called during suspend initiated from the suspend_block code.
+ */
+bool suspend_is_blocked(void)
+{
+	if (!enable_suspend_blockers)
+		return 0;
+	return !list_empty(&active_blockers);
+}
+
+static void suspend_worker(struct work_struct *work)
+{
+	int ret;
+	int entry_event_num;
+
+	enable_suspend_blockers = true;
+	while (!suspend_is_blocked()) {
+		entry_event_num = current_event_num;
+
+		if (debug_mask & DEBUG_SUSPEND)
+			pr_info("suspend: enter suspend\n");
+
+		ret = pm_suspend(requested_suspend_state);
+
+		if (debug_mask & DEBUG_EXIT_SUSPEND)
+			pr_info_time("suspend: exit suspend, ret = %d ", ret);
+
+		if (current_event_num == entry_event_num)
+			pr_info("suspend: pm_suspend returned with no event\n");
+	}
+	enable_suspend_blockers = false;
+}
+static DECLARE_WORK(suspend_work, suspend_worker);
+
+/**
+ * suspend_blocker_init() - Initialize a suspend blocker
+ * @blocker:	The suspend blocker to initialize.
+ * @name:	The name of the suspend blocker to show in debug messages.
+ *
+ * The suspend blocker struct and name must not be freed before calling
+ * suspend_blocker_destroy.
+ */
+void suspend_blocker_init(struct suspend_blocker *blocker, const char *name)
+{
+	unsigned long irqflags = 0;
+
+	WARN_ON(!name);
+
+	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
+		pr_info("suspend_blocker_init name=%s\n", name);
+
+	blocker->name = name;
+	blocker->flags = SB_INITIALIZED;
+	INIT_LIST_HEAD(&blocker->link);
+
+	spin_lock_irqsave(&list_lock, irqflags);
+	list_add(&blocker->link, &inactive_blockers);
+	spin_unlock_irqrestore(&list_lock, irqflags);
+}
+EXPORT_SYMBOL(suspend_blocker_init);
+
+/**
+ * suspend_blocker_destroy() - Destroy a suspend blocker
+ * @blocker:	The suspend blocker to destroy.
+ */
+void suspend_blocker_destroy(struct suspend_blocker *blocker)
+{
+	unsigned long irqflags;
+	if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
+		return;
+
+	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
+		pr_info("suspend_blocker_destroy name=%s\n", blocker->name);
+
+	spin_lock_irqsave(&list_lock, irqflags);
+	blocker->flags &= ~SB_INITIALIZED;
+	list_del(&blocker->link);
+	if ((blocker->flags & SB_ACTIVE) && list_empty(&active_blockers))
+		queue_work(suspend_work_queue, &suspend_work);
+	spin_unlock_irqrestore(&list_lock, irqflags);
+}
+EXPORT_SYMBOL(suspend_blocker_destroy);
+
+/**
+ * suspend_block() - Block suspend
+ * @blocker:	The suspend blocker to use
+ *
+ * It is safe to call this function from interrupt context.
+ */
+void suspend_block(struct suspend_blocker *blocker)
+{
+	unsigned long irqflags;
+
+	if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
+		return;
+
+	spin_lock_irqsave(&list_lock, irqflags);
+	blocker->flags |= SB_ACTIVE;
+	list_del(&blocker->link);
+
+	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
+		pr_info("suspend_block: %s\n", blocker->name);
+
+	list_add(&blocker->link, &active_blockers);
+
+	current_event_num++;
+	spin_unlock_irqrestore(&list_lock, irqflags);
+}
+EXPORT_SYMBOL(suspend_block);
+
+/**
+ * suspend_unblock() - Unblock suspend
+ * @blocker:	The suspend blocker to unblock.
+ *
+ * If no other suspend blockers block suspend, the system will suspend.
+ *
+ * It is safe to call this function from interrupt context.
+ */
+void suspend_unblock(struct suspend_blocker *blocker)
+{
+	unsigned long irqflags;
+
+	if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
+		return;
+
+	spin_lock_irqsave(&list_lock, irqflags);
+
+	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
+		pr_info("suspend_unblock: %s\n", blocker->name);
+
+	list_del(&blocker->link);
+	list_add(&blocker->link, &inactive_blockers);
+
+	if ((blocker->flags & SB_ACTIVE) && list_empty(&active_blockers))
+		queue_work(suspend_work_queue, &suspend_work);
+	blocker->flags &= ~(SB_ACTIVE);
+	if (blocker == &main_suspend_blocker) {
+		if (debug_mask & DEBUG_SUSPEND)
+			print_active_blockers_locked();
+	}
+	spin_unlock_irqrestore(&list_lock, irqflags);
+}
+EXPORT_SYMBOL(suspend_unblock);
+
+/**
+ * suspend_blocker_is_active() - Test if a suspend blocker is blocking suspend
+ * @blocker:	The suspend blocker to check.
+ *
+ * Returns true if the suspend_blocker is currently active.
+ */
+bool suspend_blocker_is_active(struct suspend_blocker *blocker)
+{
+	WARN_ON(!(blocker->flags & SB_INITIALIZED));
+
+	return !!(blocker->flags & SB_ACTIVE);
+}
+EXPORT_SYMBOL(suspend_blocker_is_active);
+
+bool request_suspend_valid_state(suspend_state_t state)
+{
+	return (state == PM_SUSPEND_ON) || valid_state(state);
+}
+
+int request_suspend_state(suspend_state_t state)
+{
+	unsigned long irqflags;
+
+	if (!request_suspend_valid_state(state))
+		return -ENODEV;
+
+	spin_lock_irqsave(&state_lock, irqflags);
+
+	if (debug_mask & DEBUG_USER_STATE)
+		pr_info_time("request_suspend_state: %s (%d->%d) at %lld ",
+			     state != PM_SUSPEND_ON ? "sleep" : "wakeup",
+			     requested_suspend_state, state,
+			     ktime_to_ns(ktime_get()));
+
+	requested_suspend_state = state;
+	if (state == PM_SUSPEND_ON)
+		suspend_block(&main_suspend_blocker);
+	else
+		suspend_unblock(&main_suspend_blocker);
+	spin_unlock_irqrestore(&state_lock, irqflags);
+	return 0;
+}
+
+static int __init suspend_block_init(void)
+{
+	suspend_work_queue = create_singlethread_workqueue("suspend");
+	if (!suspend_work_queue)
+		return -ENOMEM;
+
+	suspend_blocker_init(&main_suspend_blocker, "main");
+	suspend_block(&main_suspend_blocker);
+	return 0;
+}
+
+core_initcall(suspend_block_init);
-- 
1.6.5.1

[PATCH 2/8] PM: suspend_block: Add driver to access suspend blockers from user-space

[Arve Hjønnevåg]

Add a misc device, "suspend_blocker", that allows user-space processes
to block auto suspend. The device has ioctls to create a suspend_blocker,
and to block and unblock suspend. To delete the suspend_blocker, close
the device.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 Documentation/ioctl/ioctl-number.txt          |    3 +-
 Documentation/power/opportunistic-suspend.txt |   17 ++++
 include/linux/suspend_block_dev.h             |   25 +++++
 kernel/power/Kconfig                          |    9 ++
 kernel/power/Makefile                         |    1 +
 kernel/power/user_suspend_blocker.c           |  128 +++++++++++++++++++++++++
 6 files changed, 182 insertions(+), 1 deletions(-)
 create mode 100644 include/linux/suspend_block_dev.h
 create mode 100644 kernel/power/user_suspend_blocker.c

diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt
index dd5806f..e2458f7 100644
--- a/Documentation/ioctl/ioctl-number.txt
+++ b/Documentation/ioctl/ioctl-number.txt
@@ -254,7 +254,8 @@ Code  Seq#(hex)	Include File		Comments
 'q'	80-FF	linux/telephony.h	Internet PhoneJACK, Internet LineJACK
 		linux/ixjuser.h		<http://www.quicknet.net>
 'r'	00-1F	linux/msdos_fs.h and fs/fat/dir.c
-'s'	all	linux/cdk.h
+'s'	all	linux/cdk.h	conflict!
+'s'	all	linux/suspend_block_dev.h	conflict!
 't'	00-7F	linux/if_ppp.h
 't'	80-8F	linux/isdn_ppp.h
 't'	90	linux/toshiba.h
diff --git a/Documentation/power/opportunistic-suspend.txt b/Documentation/power/opportunistic-suspend.txt
index 1a29d10..639da73 100644
--- a/Documentation/power/opportunistic-suspend.txt
+++ b/Documentation/power/opportunistic-suspend.txt
@@ -112,3 +112,20 @@ if (list_empty(&state->pending_work))
 else
 	suspend_block(&state->suspend_blocker);
 
+User-space API
+==============
+
+To create a suspend_blocker from user-space, open the suspend_blocker device:
+    fd = open("/dev/suspend_blocker", O_RDWR | O_CLOEXEC);
+then call:
+    ioctl(fd, SUSPEND_BLOCKER_IOCTL_INIT(strlen(name)), name);
+
+To activate a suspend_blocker call:
+    ioctl(fd, SUSPEND_BLOCKER_IOCTL_BLOCK);
+
+To unblock call:
+    ioctl(fd, SUSPEND_BLOCKER_IOCTL_UNBLOCK);
+
+To destroy the suspend_blocker, close the device:
+    close(fd);
+
diff --git a/include/linux/suspend_block_dev.h b/include/linux/suspend_block_dev.h
new file mode 100644
index 0000000..24bc5c7
--- /dev/null
+++ b/include/linux/suspend_block_dev.h
@@ -0,0 +1,25 @@
+/* include/linux/suspend_block_dev.h
+ *
+ * Copyright (C) 2009 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#ifndef _LINUX_SUSPEND_BLOCK_DEV_H
+#define _LINUX_SUSPEND_BLOCK_DEV_H
+
+#include <linux/ioctl.h>
+
+#define SUSPEND_BLOCKER_IOCTL_INIT(len)		_IOC(_IOC_WRITE, 's', 0, len)
+#define SUSPEND_BLOCKER_IOCTL_BLOCK		_IO('s', 1)
+#define SUSPEND_BLOCKER_IOCTL_UNBLOCK		_IO('s', 2)
+
+#endif
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 55a06a1..fe5a2f2 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -146,6 +146,15 @@ config OPPORTUNISTIC_SUSPEND
 	  determines the sleep state the system will be put into when there are
 	  no active suspend blockers.
 
+config USER_SUSPEND_BLOCKERS
+	bool "Userspace suspend blockers"
+	depends on OPPORTUNISTIC_SUSPEND
+	default y
+	---help---
+	  User-space suspend block api. Creates a misc device with ioctls
+	  to create, block and unblock a suspend_blocker. The suspend_blocker
+	  will be deleted when the device is closed.
+
 config HIBERNATION_NVS
 	bool
 
diff --git a/kernel/power/Makefile b/kernel/power/Makefile
index ee5276d..78f703b 100644
--- a/kernel/power/Makefile
+++ b/kernel/power/Makefile
@@ -8,6 +8,7 @@ obj-$(CONFIG_PM_SLEEP)		+= console.o
 obj-$(CONFIG_FREEZER)		+= process.o
 obj-$(CONFIG_SUSPEND)		+= suspend.o
 obj-$(CONFIG_OPPORTUNISTIC_SUSPEND)	+= suspend_blocker.o
+obj-$(CONFIG_USER_SUSPEND_BLOCKERS)	+= user_suspend_blocker.o
 obj-$(CONFIG_PM_TEST_SUSPEND)	+= suspend_test.o
 obj-$(CONFIG_HIBERNATION)	+= hibernate.o snapshot.o swap.o user.o
 obj-$(CONFIG_HIBERNATION_NVS)	+= hibernate_nvs.o
diff --git a/kernel/power/user_suspend_blocker.c b/kernel/power/user_suspend_blocker.c
new file mode 100644
index 0000000..a9be6f4
--- /dev/null
+++ b/kernel/power/user_suspend_blocker.c
@@ -0,0 +1,128 @@
+/* kernel/power/user_suspend_block.c
+ *
+ * Copyright (C) 2009-2010 Google, Inc.
+ *
+ * This software is licensed under the terms of the GNU General Public
+ * License version 2, as published by the Free Software Foundation, and
+ * may be copied, distributed, and modified under those terms.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/uaccess.h>
+#include <linux/slab.h>
+#include <linux/suspend_blocker.h>
+#include <linux/suspend_block_dev.h>
+
+enum {
+	DEBUG_FAILURE	= BIT(0),
+};
+static int debug_mask = DEBUG_FAILURE;
+module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
+
+static DEFINE_MUTEX(ioctl_lock);
+
+struct user_suspend_blocker {
+	struct suspend_blocker	blocker;
+	char			name[0];
+};
+
+static int create_user_suspend_blocker(struct file *file, void __user *name,
+				 size_t name_len)
+{
+	struct user_suspend_blocker *bl;
+	if (file->private_data)
+		return -EBUSY;
+	if (name_len > NAME_MAX)
+		return -ENAMETOOLONG;
+	bl = kzalloc(sizeof(*bl) + name_len + 1, GFP_KERNEL);
+	if (!bl)
+		return -ENOMEM;
+	if (copy_from_user(bl->name, name, name_len))
+		goto err_fault;
+	suspend_blocker_init(&bl->blocker, bl->name);
+	file->private_data = bl;
+	return 0;
+
+err_fault:
+	kfree(bl);
+	return -EFAULT;
+}
+
+static long user_suspend_blocker_ioctl(struct file *file, unsigned int cmd,
+				unsigned long _arg)
+{
+	void __user *arg = (void __user *)_arg;
+	struct user_suspend_blocker *bl;
+	long ret;
+
+	mutex_lock(&ioctl_lock);
+	if ((cmd & ~IOCSIZE_MASK) == SUSPEND_BLOCKER_IOCTL_INIT(0)) {
+		ret = create_user_suspend_blocker(file, arg, _IOC_SIZE(cmd));
+		goto done;
+	}
+	bl = file->private_data;
+	if (!bl) {
+		ret = -ENOENT;
+		goto done;
+	}
+	switch (cmd) {
+	case SUSPEND_BLOCKER_IOCTL_BLOCK:
+		suspend_block(&bl->blocker);
+		ret = 0;
+		break;
+	case SUSPEND_BLOCKER_IOCTL_UNBLOCK:
+		suspend_unblock(&bl->blocker);
+		ret = 0;
+		break;
+	default:
+		ret = -ENOTSUPP;
+	}
+done:
+	if (ret && debug_mask & DEBUG_FAILURE)
+		pr_err("user_suspend_blocker_ioctl: cmd %x failed, %ld\n",
+			cmd, ret);
+	mutex_unlock(&ioctl_lock);
+	return ret;
+}
+
+static int user_suspend_blocker_release(struct inode *inode, struct file *file)
+{
+	struct user_suspend_blocker *bl = file->private_data;
+	if (!bl)
+		return 0;
+	suspend_blocker_destroy(&bl->blocker);
+	kfree(bl);
+	return 0;
+}
+
+const struct file_operations user_suspend_blocker_fops = {
+	.release = user_suspend_blocker_release,
+	.unlocked_ioctl = user_suspend_blocker_ioctl,
+};
+
+struct miscdevice user_suspend_blocker_device = {
+	.minor = MISC_DYNAMIC_MINOR,
+	.name = "suspend_blocker",
+	.fops = &user_suspend_blocker_fops,
+};
+
+static int __init user_suspend_blocker_init(void)
+{
+	return misc_register(&user_suspend_blocker_device);
+}
+
+static void __exit user_suspend_blocker_exit(void)
+{
+	misc_deregister(&user_suspend_blocker_device);
+}
+
+module_init(user_suspend_blocker_init);
+module_exit(user_suspend_blocker_exit);
-- 
1.6.5.1

[PATCH 3/8] PM: suspend_block: Abort task freezing if a suspend_blocker is active.

[Arve Hjønnevåg]

If a suspend_blocker is active, suspend will fail anyway. Since
try_to_freeze_tasks can take up to 20 seconds to complete or fail, aborting
as soon as someone blocks suspend (e.g. from an interrupt handler) improves
the worst case wakeup latency.

On an older kernel where task freezing could fail for processes attached
to a debugger, this fixed a problem where the device sometimes hung for
20 seconds before the screen turned on.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 kernel/power/process.c |   12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/kernel/power/process.c b/kernel/power/process.c
index 71ae290..d8ebd50 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -15,6 +15,7 @@
 #include <linux/syscalls.h>
 #include <linux/freezer.h>
 #include <linux/delay.h>
+#include <linux/suspend_blocker.h>
 
 /* 
  * Timeout for stopping processes
@@ -38,6 +39,7 @@ static int try_to_freeze_tasks(bool sig_only)
 	struct timeval start, end;
 	u64 elapsed_csecs64;
 	unsigned int elapsed_csecs;
+	bool wakeup = false;
 
 	do_gettimeofday(&start);
 
@@ -63,6 +65,10 @@ static int try_to_freeze_tasks(bool sig_only)
 				todo++;
 		} while_each_thread(g, p);
 		read_unlock(&tasklist_lock);
+		if (todo && suspend_is_blocked()) {
+			wakeup = true;
+			break;
+		}
 		if (!todo || time_after(jiffies, end_time))
 			break;
 
@@ -85,13 +91,15 @@ static int try_to_freeze_tasks(bool sig_only)
 		 * but it cleans up leftover PF_FREEZE requests.
 		 */
 		printk("\n");
-		printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
+		printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
 				"(%d tasks refusing to freeze):\n",
+				wakeup ? "aborted" : "failed",
 				elapsed_csecs / 100, elapsed_csecs % 100, todo);
 		read_lock(&tasklist_lock);
 		do_each_thread(g, p) {
 			task_lock(p);
-			if (freezing(p) && !freezer_should_skip(p))
+			if (freezing(p) && !freezer_should_skip(p)
+					&& elapsed_csecs > 100)
 				sched_show_task(p);
 			cancel_freezing(p);
 			task_unlock(p);
-- 
1.6.5.1

[PATCH 4/8] PM: suspend_block: Add debugfs file

[Arve Hjønnevåg]

Report active and inactive suspend blockers in
/sys/kernel/debug/suspend_blockers.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 kernel/power/suspend_blocker.c |   44 ++++++++++++++++++++++++++++++++++++++-
 1 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/kernel/power/suspend_blocker.c b/kernel/power/suspend_blocker.c
index 9459361..ee43490 100644
--- a/kernel/power/suspend_blocker.c
+++ b/kernel/power/suspend_blocker.c
@@ -17,6 +17,7 @@
 #include <linux/rtc.h>
 #include <linux/suspend.h>
 #include <linux/suspend_blocker.h>
+#include <linux/debugfs.h>
 #include "power.h"
 
 enum {
@@ -41,6 +42,7 @@ struct workqueue_struct *suspend_work_queue;
 struct suspend_blocker main_suspend_blocker;
 static suspend_state_t requested_suspend_state = PM_SUSPEND_MEM;
 static bool enable_suspend_blockers;
+static struct dentry *suspend_blocker_stats_dentry;
 
 #define pr_info_time(fmt, args...) \
 	do { \
@@ -54,6 +56,21 @@ static bool enable_suspend_blockers;
 			tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec); \
 	} while (0);
 
+static int suspend_blocker_stats_show(struct seq_file *m, void *unused)
+{
+	unsigned long irqflags;
+	struct suspend_blocker *blocker;
+
+	seq_puts(m, "name\tactive\n");
+	spin_lock_irqsave(&list_lock, irqflags);
+	list_for_each_entry(blocker, &inactive_blockers, link)
+		seq_printf(m, "\"%s\"\t0\n", blocker->name);
+	list_for_each_entry(blocker, &active_blockers, link)
+		seq_printf(m, "\"%s\"\t1\n", blocker->name);
+	spin_unlock_irqrestore(&list_lock, irqflags);
+	return 0;
+}
+
 static void print_active_blockers_locked(void)
 {
 	struct suspend_blocker *blocker;
@@ -105,8 +122,8 @@ static DECLARE_WORK(suspend_work, suspend_worker);
 /**
  * suspend_blocker_init() - Initialize a suspend blocker
  * @blocker:	The suspend blocker to initialize.
- * @name:	The name of the suspend blocker to show in debug messages.
- *
+ * @name:	The name of the suspend blocker to show in debug messages and
+ *		/sys/kernel/debug/suspend_blockers.
  * The suspend blocker struct and name must not be freed before calling
  * suspend_blocker_destroy.
  */
@@ -255,6 +272,19 @@ int request_suspend_state(suspend_state_t state)
 	return 0;
 }
 
+static int suspend_blocker_stats_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, suspend_blocker_stats_show, NULL);
+}
+
+static const struct file_operations suspend_blocker_stats_fops = {
+	.owner = THIS_MODULE,
+	.open = suspend_blocker_stats_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
+
 static int __init suspend_block_init(void)
 {
 	suspend_work_queue = create_singlethread_workqueue("suspend");
@@ -266,4 +296,14 @@ static int __init suspend_block_init(void)
 	return 0;
 }
 
+static int __init suspend_block_postcore_init(void)
+{
+	if (!suspend_work_queue)
+		return 0;
+	suspend_blocker_stats_dentry = debugfs_create_file("suspend_blockers",
+			S_IRUGO, NULL, NULL, &suspend_blocker_stats_fops);
+	return 0;
+}
+
 core_initcall(suspend_block_init);
+postcore_initcall(suspend_block_postcore_init);
-- 
1.6.5.1

[PATCH 5/8] PM: suspend_block: Add suspend_blocker stats

[Arve Hjønnevåg]

Report suspend block stats in /sys/kernel/debug/suspend_blockers.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 include/linux/suspend_blocker.h |   21 ++++-
 kernel/power/Kconfig            |    7 ++
 kernel/power/power.h            |    6 +-
 kernel/power/suspend.c          |    4 +-
 kernel/power/suspend_blocker.c  |  191 +++++++++++++++++++++++++++++++++++++--
 5 files changed, 219 insertions(+), 10 deletions(-)

diff --git a/include/linux/suspend_blocker.h b/include/linux/suspend_blocker.h
index f9928cc..c80764c 100755
--- a/include/linux/suspend_blocker.h
+++ b/include/linux/suspend_blocker.h
@@ -17,12 +17,21 @@
 #define _LINUX_SUSPEND_BLOCKER_H
 
 #include <linux/list.h>
+#include <linux/ktime.h>
 
 /**
  * struct suspend_blocker - the basic suspend_blocker structure
  * @link:	List entry for active or inactive list.
- * @flags:	Tracks initialized and active state.
+ * @flags:	Tracks initialized, active and stats state.
  * @name:	Name used for debugging.
+ * @count:	Number of times this blocker has been deacivated
+ * @wakeup_count: Number of times this blocker was the first to block suspend
+ *		after resume.
+ * @total_time:	Total time this suspend blocker has prevented suspend.
+ * @prevent_suspend_time: Time this suspend blocker has prevented suspend while
+ *		user-space requested suspend.
+ * @max_time:	Max time this suspend blocker has been continuously active
+ * @last_time:	Monotonic clock when the active state last changed.
  *
  * When a suspend_blocker is active it prevents the system from entering
  * opportunistic suspend.
@@ -35,6 +44,16 @@ struct suspend_blocker {
 	struct list_head    link;
 	int                 flags;
 	const char         *name;
+#ifdef CONFIG_SUSPEND_BLOCKER_STATS
+	struct {
+		int             count;
+		int             wakeup_count;
+		ktime_t         total_time;
+		ktime_t         prevent_suspend_time;
+		ktime_t         max_time;
+		ktime_t         last_time;
+	} stat;
+#endif
 #endif
 };
 
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index fe5a2f2..4bcba07 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -146,6 +146,13 @@ config OPPORTUNISTIC_SUSPEND
 	  determines the sleep state the system will be put into when there are
 	  no active suspend blockers.
 
+config SUSPEND_BLOCKER_STATS
+	bool "Suspend block stats"
+	depends on OPPORTUNISTIC_SUSPEND
+	default y
+	---help---
+	  Report suspend block stats in /sys/kernel/debug/suspend_blockers
+
 config USER_SUSPEND_BLOCKERS
 	bool "Userspace suspend blockers"
 	depends on OPPORTUNISTIC_SUSPEND
diff --git a/kernel/power/power.h b/kernel/power/power.h
index 9b468d7..75b8849 100644
--- a/kernel/power/power.h
+++ b/kernel/power/power.h
@@ -240,4 +240,8 @@ static inline void suspend_thaw_processes(void)
 /* kernel/power/suspend_block.c */
 extern int request_suspend_state(suspend_state_t state);
 extern bool request_suspend_valid_state(suspend_state_t state);
-
+#ifdef CONFIG_SUSPEND_BLOCKER_STATS
+void about_to_enter_suspend(void);
+#else
+static inline void about_to_enter_suspend(void) {}
+#endif
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index dc42006..6d327ea 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -159,8 +159,10 @@ static int suspend_enter(suspend_state_t state)
 
 	error = sysdev_suspend(PMSG_SUSPEND);
 	if (!error) {
-		if (!suspend_is_blocked() && !suspend_test(TEST_CORE))
+		if (!suspend_is_blocked() && !suspend_test(TEST_CORE)) {
+			about_to_enter_suspend();
 			error = suspend_ops->enter(state);
+		}
 		sysdev_resume();
 	}
 
diff --git a/kernel/power/suspend_blocker.c b/kernel/power/suspend_blocker.c
index ee43490..2d43f37 100644
--- a/kernel/power/suspend_blocker.c
+++ b/kernel/power/suspend_blocker.c
@@ -32,6 +32,7 @@ module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
 
 #define SB_INITIALIZED            (1U << 8)
 #define SB_ACTIVE                 (1U << 9)
+#define SB_PREVENTING_SUSPEND     (1U << 10)
 
 static DEFINE_SPINLOCK(list_lock);
 static DEFINE_SPINLOCK(state_lock);
@@ -42,6 +43,7 @@ struct workqueue_struct *suspend_work_queue;
 struct suspend_blocker main_suspend_blocker;
 static suspend_state_t requested_suspend_state = PM_SUSPEND_MEM;
 static bool enable_suspend_blockers;
+static struct suspend_blocker unknown_wakeup;
 static struct dentry *suspend_blocker_stats_dentry;
 
 #define pr_info_time(fmt, args...) \
@@ -56,6 +58,153 @@ static struct dentry *suspend_blocker_stats_dentry;
 			tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec); \
 	} while (0);
 
+#ifdef CONFIG_SUSPEND_BLOCKER_STATS
+static struct suspend_blocker deleted_suspend_blockers;
+static ktime_t last_sleep_time_update;
+static bool wait_for_wakeup;
+
+static int print_blocker_stat(struct seq_file *m,
+			      struct suspend_blocker *blocker)
+{
+	int lock_count = blocker->stat.count;
+	ktime_t active_time = ktime_set(0, 0);
+	ktime_t total_time = blocker->stat.total_time;
+	ktime_t max_time = blocker->stat.max_time;
+	ktime_t prevent_suspend_time = blocker->stat.prevent_suspend_time;
+	if (blocker->flags & SB_ACTIVE) {
+		ktime_t now, add_time;
+		now = ktime_get();
+		add_time = ktime_sub(now, blocker->stat.last_time);
+		lock_count++;
+		active_time = add_time;
+		total_time = ktime_add(total_time, add_time);
+		if (blocker->flags & SB_PREVENTING_SUSPEND)
+			prevent_suspend_time = ktime_add(prevent_suspend_time,
+					ktime_sub(now, last_sleep_time_update));
+		if (add_time.tv64 > max_time.tv64)
+			max_time = add_time;
+	}
+
+	return seq_printf(m, "\"%s\"\t%d\t%d\t%lld\t%lld\t%lld\t%lld\t%lld\n",
+		       blocker->name, lock_count, blocker->stat.wakeup_count,
+		       ktime_to_ns(active_time), ktime_to_ns(total_time),
+		       ktime_to_ns(prevent_suspend_time), ktime_to_ns(max_time),
+		       ktime_to_ns(blocker->stat.last_time));
+}
+
+
+static int suspend_blocker_stats_show(struct seq_file *m, void *unused)
+{
+	unsigned long irqflags;
+	struct suspend_blocker *blocker;
+
+	seq_puts(m, "name\tcount\twake_count\tactive_since"
+		 "\ttotal_time\tsleep_time\tmax_time\tlast_change\n");
+	spin_lock_irqsave(&list_lock, irqflags);
+	list_for_each_entry(blocker, &inactive_blockers, link)
+		print_blocker_stat(m, blocker);
+	list_for_each_entry(blocker, &active_blockers, link)
+		print_blocker_stat(m, blocker);
+	spin_unlock_irqrestore(&list_lock, irqflags);
+	return 0;
+}
+
+static void suspend_blocker_stat_init_locked(struct suspend_blocker *blocker)
+{
+	blocker->stat.count = 0;
+	blocker->stat.wakeup_count = 0;
+	blocker->stat.total_time = ktime_set(0, 0);
+	blocker->stat.prevent_suspend_time = ktime_set(0, 0);
+	blocker->stat.max_time = ktime_set(0, 0);
+	blocker->stat.last_time = ktime_set(0, 0);
+}
+
+static void suspend_blocker_stat_destroy_locked(struct suspend_blocker *bl)
+{
+	if (!bl->stat.count)
+		return;
+	deleted_suspend_blockers.stat.count += bl->stat.count;
+	deleted_suspend_blockers.stat.total_time = ktime_add(
+		deleted_suspend_blockers.stat.total_time, bl->stat.total_time);
+	deleted_suspend_blockers.stat.prevent_suspend_time = ktime_add(
+		deleted_suspend_blockers.stat.prevent_suspend_time,
+		bl->stat.prevent_suspend_time);
+	deleted_suspend_blockers.stat.max_time = ktime_add(
+		deleted_suspend_blockers.stat.max_time, bl->stat.max_time);
+}
+
+static void suspend_unblock_stat_locked(struct suspend_blocker *blocker)
+{
+	ktime_t duration;
+	ktime_t now;
+	if (!(blocker->flags & SB_ACTIVE))
+		return;
+	now = ktime_get();
+	blocker->stat.count++;
+	duration = ktime_sub(now, blocker->stat.last_time);
+	blocker->stat.total_time =
+		ktime_add(blocker->stat.total_time, duration);
+	if (ktime_to_ns(duration) > ktime_to_ns(blocker->stat.max_time))
+		blocker->stat.max_time = duration;
+	blocker->stat.last_time = ktime_get();
+	if (blocker->flags & SB_PREVENTING_SUSPEND) {
+		duration = ktime_sub(now, last_sleep_time_update);
+		blocker->stat.prevent_suspend_time = ktime_add(
+			blocker->stat.prevent_suspend_time, duration);
+		blocker->flags &= ~SB_PREVENTING_SUSPEND;
+	}
+}
+
+static void suspend_block_stat_locked(struct suspend_blocker *blocker)
+{
+	if (wait_for_wakeup) {
+		if (debug_mask & DEBUG_WAKEUP)
+			pr_info("wakeup suspend blocker: %s\n", blocker->name);
+		wait_for_wakeup = false;
+		blocker->stat.wakeup_count++;
+	}
+	if (!(blocker->flags & SB_ACTIVE))
+		blocker->stat.last_time = ktime_get();
+}
+
+static void update_sleep_wait_stats_locked(bool done)
+{
+	struct suspend_blocker *blocker;
+	ktime_t now, elapsed, add;
+
+	now = ktime_get();
+	elapsed = ktime_sub(now, last_sleep_time_update);
+	list_for_each_entry(blocker, &active_blockers, link) {
+		if (blocker->flags & SB_PREVENTING_SUSPEND) {
+			add = elapsed;
+			blocker->stat.prevent_suspend_time = ktime_add(
+				blocker->stat.prevent_suspend_time, add);
+		}
+		if (done)
+			blocker->flags &= ~SB_PREVENTING_SUSPEND;
+		else
+			blocker->flags |= SB_PREVENTING_SUSPEND;
+	}
+	last_sleep_time_update = now;
+}
+
+void about_to_enter_suspend(void)
+{
+	wait_for_wakeup = true;
+}
+
+#else
+
+static inline void suspend_blocker_stat_init_locked(
+					struct suspend_blocker *blocker) {}
+static inline void suspend_blocker_stat_destroy_locked(
+					struct suspend_blocker *blocker) {}
+static inline void suspend_block_stat_locked(
+					struct suspend_blocker *blocker) {}
+static inline void suspend_unblock_stat_locked(
+					struct suspend_blocker *blocker) {}
+static inline void update_sleep_wait_stats_locked(bool done) {}
+
 static int suspend_blocker_stats_show(struct seq_file *m, void *unused)
 {
 	unsigned long irqflags;
@@ -71,6 +220,8 @@ static int suspend_blocker_stats_show(struct seq_file *m, void *unused)
 	return 0;
 }
 
+#endif
+
 static void print_active_blockers_locked(void)
 {
 	struct suspend_blocker *blocker;
@@ -101,20 +252,31 @@ static void suspend_worker(struct work_struct *work)
 	int entry_event_num;
 
 	enable_suspend_blockers = true;
-	while (!suspend_is_blocked()) {
-		entry_event_num = current_event_num;
 
+	if (suspend_is_blocked()) {
 		if (debug_mask & DEBUG_SUSPEND)
-			pr_info("suspend: enter suspend\n");
+			pr_info("suspend: abort suspend\n");
+		goto abort;
+	}
+
+	entry_event_num = current_event_num;
+
+	if (debug_mask & DEBUG_SUSPEND)
+		pr_info("suspend: enter suspend\n");
 
-		ret = pm_suspend(requested_suspend_state);
+	ret = pm_suspend(requested_suspend_state);
 
-		if (debug_mask & DEBUG_EXIT_SUSPEND)
-			pr_info_time("suspend: exit suspend, ret = %d ", ret);
+	if (debug_mask & DEBUG_EXIT_SUSPEND)
+		pr_info_time("suspend: exit suspend, ret = %d ", ret);
 
-		if (current_event_num == entry_event_num)
+	if (current_event_num == entry_event_num) {
+		if (debug_mask & DEBUG_SUSPEND)
 			pr_info("suspend: pm_suspend returned with no event\n");
+
+		suspend_block(&unknown_wakeup);
+		suspend_unblock(&unknown_wakeup);
 	}
+abort:
 	enable_suspend_blockers = false;
 }
 static DECLARE_WORK(suspend_work, suspend_worker);
@@ -141,6 +303,7 @@ void suspend_blocker_init(struct suspend_blocker *blocker, const char *name)
 	INIT_LIST_HEAD(&blocker->link);
 
 	spin_lock_irqsave(&list_lock, irqflags);
+	suspend_blocker_stat_init_locked(blocker);
 	list_add(&blocker->link, &inactive_blockers);
 	spin_unlock_irqrestore(&list_lock, irqflags);
 }
@@ -160,6 +323,7 @@ void suspend_blocker_destroy(struct suspend_blocker *blocker)
 		pr_info("suspend_blocker_destroy name=%s\n", blocker->name);
 
 	spin_lock_irqsave(&list_lock, irqflags);
+	suspend_blocker_stat_destroy_locked(blocker);
 	blocker->flags &= ~SB_INITIALIZED;
 	list_del(&blocker->link);
 	if ((blocker->flags & SB_ACTIVE) && list_empty(&active_blockers))
@@ -182,6 +346,7 @@ void suspend_block(struct suspend_blocker *blocker)
 		return;
 
 	spin_lock_irqsave(&list_lock, irqflags);
+	suspend_block_stat_locked(blocker);
 	blocker->flags |= SB_ACTIVE;
 	list_del(&blocker->link);
 
@@ -191,6 +356,10 @@ void suspend_block(struct suspend_blocker *blocker)
 	list_add(&blocker->link, &active_blockers);
 
 	current_event_num++;
+	if (blocker == &main_suspend_blocker)
+		update_sleep_wait_stats_locked(true);
+	else if (!suspend_blocker_is_active(&main_suspend_blocker))
+		update_sleep_wait_stats_locked(false);
 	spin_unlock_irqrestore(&list_lock, irqflags);
 }
 EXPORT_SYMBOL(suspend_block);
@@ -212,6 +381,8 @@ void suspend_unblock(struct suspend_blocker *blocker)
 
 	spin_lock_irqsave(&list_lock, irqflags);
 
+	suspend_unblock_stat_locked(blocker);
+
 	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
 		pr_info("suspend_unblock: %s\n", blocker->name);
 
@@ -224,6 +395,7 @@ void suspend_unblock(struct suspend_blocker *blocker)
 	if (blocker == &main_suspend_blocker) {
 		if (debug_mask & DEBUG_SUSPEND)
 			print_active_blockers_locked();
+		update_sleep_wait_stats_locked(false);
 	}
 	spin_unlock_irqrestore(&list_lock, irqflags);
 }
@@ -293,6 +465,11 @@ static int __init suspend_block_init(void)
 
 	suspend_blocker_init(&main_suspend_blocker, "main");
 	suspend_block(&main_suspend_blocker);
+	suspend_blocker_init(&unknown_wakeup, "unknown_wakeups");
+#ifdef CONFIG_SUSPEND_BLOCKER_STATS
+	suspend_blocker_init(&deleted_suspend_blockers,
+				"deleted_suspend_blockers");
+#endif
 	return 0;
 }
 
-- 
1.6.5.1

[PATCH 6/8] PM: Add suspend blocking work.

[Arve Hjønnevåg]

Allow work to be queued that will block suspend while it is pending
or executing. To get the same functionality in the calling code often
requires a separate suspend_blocker for pending and executing work, or
additional state and locking. This implementation does add additional
state and locking, but this can be removed later if we add support for
suspend blocking work to the core workqueue code.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 include/linux/suspend_blocker.h |   67 ++++++++++++++++++++++++
 kernel/power/suspend_blocker.c  |  107 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 174 insertions(+), 0 deletions(-)

diff --git a/include/linux/suspend_blocker.h b/include/linux/suspend_blocker.h
index c80764c..bf41a57 100755
--- a/include/linux/suspend_blocker.h
+++ b/include/linux/suspend_blocker.h
@@ -18,6 +18,7 @@
 
 #include <linux/list.h>
 #include <linux/ktime.h>
+#include <linux/workqueue.h>
 
 /**
  * struct suspend_blocker - the basic suspend_blocker structure
@@ -57,6 +58,38 @@ struct suspend_blocker {
 #endif
 };
 
+/**
+ * struct suspend_blocking_work - the basic suspend_blocking_work structure
+ * @work:		Standard work struct.
+ * @suspend_blocker:	Suspend blocker.
+ * @func:		Callback.
+ * @lock:		Spinlock protecting pending and running state.
+ * @active:		Number of cpu workqueues where work is pending or
+ *			callback is running.
+ *
+ * When suspend blocking work is pending or its callback is running it prevents
+ * the system from entering opportunistic suspend.
+ *
+ * The suspend_blocking_work structure must be initialized by
+ * suspend_blocking_work_init().
+ */
+
+struct suspend_blocking_work {
+	struct work_struct work;
+#ifdef CONFIG_OPPORTUNISTIC_SUSPEND
+	struct suspend_blocker suspend_blocker;
+	work_func_t func;
+	spinlock_t lock;
+	int active;
+#endif
+};
+
+static inline struct suspend_blocking_work *to_suspend_blocking_work(
+	struct work_struct *work)
+{
+	return container_of(work, struct suspend_blocking_work, work);
+}
+
 #ifdef CONFIG_OPPORTUNISTIC_SUSPEND
 
 void suspend_blocker_init(struct suspend_blocker *blocker, const char *name);
@@ -66,6 +99,14 @@ void suspend_unblock(struct suspend_blocker *blocker);
 bool suspend_blocker_is_active(struct suspend_blocker *blocker);
 bool suspend_is_blocked(void);
 
+void suspend_blocking_work_init(struct suspend_blocking_work *work,
+				work_func_t func, const char *name);
+void suspend_blocking_work_destroy(struct suspend_blocking_work *work);
+int queue_suspend_blocking_work(struct workqueue_struct *wq,
+				struct suspend_blocking_work *work);
+int schedule_suspend_blocking_work(struct suspend_blocking_work *work);
+int cancel_suspend_blocking_work_sync(struct suspend_blocking_work *work);
+
 #else
 
 static inline void suspend_blocker_init(struct suspend_blocker *blocker,
@@ -77,6 +118,32 @@ static inline bool suspend_blocker_is_active(struct suspend_blocker *bl)
 								{ return 0; }
 static inline bool suspend_is_blocked(void) { return 0; }
 
+static inline void suspend_blocking_work_init(
+	struct suspend_blocking_work *work, work_func_t func, const char *name)
+{
+	INIT_WORK(&work->work, func);
+}
+static inline void suspend_blocking_work_destroy(
+	struct suspend_blocking_work *work)
+{
+	cancel_work_sync(&work->work);
+}
+static inline int queue_suspend_blocking_work(
+	struct workqueue_struct *wq, struct suspend_blocking_work *work)
+{
+	return queue_work(wq, &work->work);
+}
+static inline int schedule_suspend_blocking_work(
+	struct suspend_blocking_work *work)
+{
+	return schedule_work(&work->work);
+}
+static inline int cancel_suspend_blocking_work_sync(
+	struct suspend_blocking_work *work)
+{
+	return cancel_work_sync(&work->work);
+}
+
 #endif
 
 #endif
diff --git a/kernel/power/suspend_blocker.c b/kernel/power/suspend_blocker.c
index 2d43f37..f9c6206 100644
--- a/kernel/power/suspend_blocker.c
+++ b/kernel/power/suspend_blocker.c
@@ -484,3 +484,110 @@ static int __init suspend_block_postcore_init(void)
 
 core_initcall(suspend_block_init);
 postcore_initcall(suspend_block_postcore_init);
+
+static void suspend_blocking_work_complete(struct suspend_blocking_work *work)
+{
+	unsigned long flags;
+
+	WARN_ON(!work->active);
+	spin_lock_irqsave(&work->lock, flags);
+	if (!--work->active)
+		suspend_unblock(&work->suspend_blocker);
+	spin_unlock_irqrestore(&work->lock, flags);
+}
+
+static void suspend_blocking_work_func(struct work_struct *work)
+{
+	struct suspend_blocking_work *sbwork = to_suspend_blocking_work(work);
+
+	sbwork->func(work);
+	suspend_blocking_work_complete(sbwork);
+}
+
+/**
+ * suspend_blocking_work_init - Initialize suspend_blocking_work
+ * @work: The work item in question.
+ * @func: Callback.
+ * @name: Name for suspend blocker.
+ *
+ */
+void suspend_blocking_work_init(struct suspend_blocking_work *work,
+				work_func_t func, const char *name)
+{
+	INIT_WORK(&work->work, suspend_blocking_work_func);
+	suspend_blocker_init(&work->suspend_blocker, name);
+	work->func = func;
+	spin_lock_init(&work->lock);
+	work->active = 0;
+}
+EXPORT_SYMBOL(suspend_blocking_work_init);
+
+/**
+ * cancel_suspend_blocking_work_sync - Cancel suspend_blocking_work
+ * @work: The work item in question
+ */
+int cancel_suspend_blocking_work_sync(struct suspend_blocking_work *work)
+{
+	int ret;
+
+	ret = cancel_work_sync(&work->work);
+	if (ret)
+		suspend_blocking_work_complete(work);
+	return ret;
+}
+EXPORT_SYMBOL(cancel_suspend_blocking_work_sync);
+
+/**
+ * suspend_blocking_work_destroy - Destroy suspend_blocking_work
+ * @work: The work item in question
+ *
+ * If the work was ever queued on more then one workqueue all but the last
+ * workqueue must be flushed before calling suspend_blocking_work_destroy.
+ */
+void suspend_blocking_work_destroy(struct suspend_blocking_work *work)
+{
+	cancel_suspend_blocking_work_sync(work);
+	WARN_ON(work->active);
+	suspend_blocker_destroy(&work->suspend_blocker);
+}
+EXPORT_SYMBOL(suspend_blocking_work_destroy);
+
+/**
+ * queue_suspend_blocking_work - Queue suspend blocking work
+ * @wq:		Workqueue to queue work on.
+ * @work:	The work item in question.
+ */
+int queue_suspend_blocking_work(struct workqueue_struct *wq,
+				struct suspend_blocking_work *work)
+{
+	int ret;
+	unsigned long flags;
+
+	spin_lock_irqsave(&work->lock, flags);
+	suspend_block(&work->suspend_blocker);
+	ret = queue_work(wq, &work->work);
+	if (ret)
+		work->active++;
+	spin_unlock_irqrestore(&work->lock, flags);
+	return ret;
+}
+EXPORT_SYMBOL(queue_suspend_blocking_work);
+
+/**
+ * schedule_suspend_blocking_work - Queue suspend blocking work
+ * @work:	The work item in question.
+ */
+int schedule_suspend_blocking_work(struct suspend_blocking_work *work)
+{
+	int ret;
+	unsigned long flags;
+
+	spin_lock_irqsave(&work->lock, flags);
+	suspend_block(&work->suspend_blocker);
+	ret = schedule_work(&work->work);
+	if (ret)
+		work->active++;
+	spin_unlock_irqrestore(&work->lock, flags);
+	return ret;
+}
+EXPORT_SYMBOL(schedule_suspend_blocking_work);
-- 
1.6.5.1

[PATCH 7/8] Input: Block suspend while event queue is not empty.

[Arve Hjønnevåg]

Add an ioctl, EVIOCSSUSPENDBLOCK, to enable a suspend_blocker that will block
suspend while the event queue is not empty. This allows userspace code to
process input events while the device appears to be asleep.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 drivers/input/evdev.c |   22 ++++++++++++++++++++++
 include/linux/input.h |    3 +++
 2 files changed, 25 insertions(+), 0 deletions(-)

diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
index 2ee6c7a..66e0d16 100644
--- a/drivers/input/evdev.c
+++ b/drivers/input/evdev.c
@@ -20,6 +20,7 @@
 #include <linux/input.h>
 #include <linux/major.h>
 #include <linux/device.h>
+#include <linux/suspend_blocker.h>
 #include "input-compat.h"
 
 struct evdev {
@@ -43,6 +44,8 @@ struct evdev_client {
 	struct fasync_struct *fasync;
 	struct evdev *evdev;
 	struct list_head node;
+	struct suspend_blocker suspend_blocker;
+	bool use_suspend_blocker;
 };
 
 static struct evdev *evdev_table[EVDEV_MINORS];
@@ -55,6 +58,8 @@ static void evdev_pass_event(struct evdev_client *client,
 	 * Interrupts are disabled, just acquire the lock
 	 */
 	spin_lock(&client->buffer_lock);
+	if (client->use_suspend_blocker)
+		suspend_block(&client->suspend_blocker);
 	client->buffer[client->head++] = *event;
 	client->head &= EVDEV_BUFFER_SIZE - 1;
 	spin_unlock(&client->buffer_lock);
@@ -234,6 +239,8 @@ static int evdev_release(struct inode *inode, struct file *file)
 	mutex_unlock(&evdev->mutex);
 
 	evdev_detach_client(evdev, client);
+	if (client->use_suspend_blocker)
+		suspend_blocker_destroy(&client->suspend_blocker);
 	kfree(client);
 
 	evdev_close_device(evdev);
@@ -335,6 +342,8 @@ static int evdev_fetch_next_event(struct evdev_client *client,
 	if (have_event) {
 		*event = client->buffer[client->tail++];
 		client->tail &= EVDEV_BUFFER_SIZE - 1;
+		if (client->use_suspend_blocker && client->head == client->tail)
+			suspend_unblock(&client->suspend_blocker);
 	}
 
 	spin_unlock_irq(&client->buffer_lock);
@@ -585,6 +594,19 @@ static long evdev_do_ioctl(struct file *file, unsigned int cmd,
 		else
 			return evdev_ungrab(evdev, client);
 
+	case EVIOCGSUSPENDBLOCK:
+		return put_user(client->use_suspend_blocker, ip);
+
+	case EVIOCSSUSPENDBLOCK:
+		spin_lock_irq(&client->buffer_lock);
+		if (!client->use_suspend_blocker && p)
+			suspend_blocker_init(&client->suspend_blocker, "evdev");
+		else if (client->use_suspend_blocker && !p)
+			suspend_blocker_destroy(&client->suspend_blocker);
+		client->use_suspend_blocker = !!p;
+		spin_unlock_irq(&client->buffer_lock);
+		return 0;
+
 	default:
 
 		if (_IOC_TYPE(cmd) != 'E')
diff --git a/include/linux/input.h b/include/linux/input.h
index 7ed2251..b2d93b4 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -82,6 +82,9 @@ struct input_absinfo {
 
 #define EVIOCGRAB		_IOW('E', 0x90, int)			/* Grab/Release device */
 
+#define EVIOCGSUSPENDBLOCK	_IOR('E', 0x91, int)			/* get suspend block enable */
+#define EVIOCSSUSPENDBLOCK	_IOW('E', 0x91, int)			/* set suspend block enable */
+
 /*
  * Event types
  */
-- 
1.6.5.1

[PATCH 8/8] power_supply: Block suspend while power supply change notifications are pending

[Arve Hjønnevåg]

When connecting usb or the charger the device would often go back to sleep
before the charge led and screen turned on.

Signed-off-by: Arve Hjønnevåg <arve@android.com>
---
 drivers/power/power_supply_core.c |    9 ++++++---
 include/linux/power_supply.h      |    3 ++-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/power/power_supply_core.c b/drivers/power/power_supply_core.c
index cce75b4..577a131 100644
--- a/drivers/power/power_supply_core.c
+++ b/drivers/power/power_supply_core.c
@@ -39,7 +39,7 @@ static int __power_supply_changed_work(struct device *dev, void *data)
 static void power_supply_changed_work(struct work_struct *work)
 {
 	struct power_supply *psy = container_of(work, struct power_supply,
-						changed_work);
+						changed_work.work);
 
 	dev_dbg(psy->dev, "%s\n", __func__);
 
@@ -55,7 +55,7 @@ void power_supply_changed(struct power_supply *psy)
 {
 	dev_dbg(psy->dev, "%s\n", __func__);
 
-	schedule_work(&psy->changed_work);
+	schedule_suspend_blocking_work(&psy->changed_work);
 }
 EXPORT_SYMBOL_GPL(power_supply_changed);
 
@@ -155,7 +155,8 @@ int power_supply_register(struct device *parent, struct power_supply *psy)
 		goto dev_create_failed;
 	}
 
-	INIT_WORK(&psy->changed_work, power_supply_changed_work);
+	suspend_blocking_work_init(&psy->changed_work,
+				   power_supply_changed_work, "power-supply");
 
 	rc = power_supply_create_attrs(psy);
 	if (rc)
@@ -172,6 +173,7 @@ int power_supply_register(struct device *parent, struct power_supply *psy)
 create_triggers_failed:
 	power_supply_remove_attrs(psy);
 create_attrs_failed:
+	suspend_blocking_work_destroy(&psy->changed_work);
 	device_unregister(psy->dev);
 dev_create_failed:
 success:
@@ -184,6 +186,7 @@ void power_supply_unregister(struct power_supply *psy)
 	flush_scheduled_work();
 	power_supply_remove_triggers(psy);
 	power_supply_remove_attrs(psy);
+	suspend_blocking_work_destroy(&psy->changed_work);
 	device_unregister(psy->dev);
 }
 EXPORT_SYMBOL_GPL(power_supply_unregister);
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
index ebd2b8f..8a12d50 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -14,6 +14,7 @@
 #define __LINUX_POWER_SUPPLY_H__
 
 #include <linux/device.h>
+#include <linux/suspend_blocker.h>
 #include <linux/workqueue.h>
 #include <linux/leds.h>
 
@@ -152,7 +153,7 @@ struct power_supply {
 
 	/* private */
 	struct device *dev;
-	struct work_struct changed_work;
+	struct suspend_blocking_work changed_work;
 
 #ifdef CONFIG_LEDS_TRIGGERS
 	struct led_trigger *charging_full_trig;
-- 
1.6.5.1

Re: [PATCH 3/8] PM: suspend_block: Abort task freezing if a suspend_blocker is active.

[Pavel Machek]

On Tue 2010-04-27 21:31:54, Arve Hj??nnev??g wrote:
> If a suspend_blocker is active, suspend will fail anyway. Since
> try_to_freeze_tasks can take up to 20 seconds to complete or fail, aborting
> as soon as someone blocks suspend (e.g. from an interrupt handler) improves
> the worst case wakeup latency.
> 
> On an older kernel where task freezing could fail for processes attached
> to a debugger, this fixed a problem where the device sometimes hung for
> 20 seconds before the screen turned on.
> 
> Signed-off-by: Arve Hj??nnev??g <arve@android.com>

ack.

> ---
>  kernel/power/process.c |   12 ++++++++++--
>  1 files changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/power/process.c b/kernel/power/process.c
> index 71ae290..d8ebd50 100644
> --- a/kernel/power/process.c
> +++ b/kernel/power/process.c
> @@ -15,6 +15,7 @@
>  #include <linux/syscalls.h>
>  #include <linux/freezer.h>
>  #include <linux/delay.h>
> +#include <linux/suspend_blocker.h>
>  
>  /* 
>   * Timeout for stopping processes
> @@ -38,6 +39,7 @@ static int try_to_freeze_tasks(bool sig_only)
>  	struct timeval start, end;
>  	u64 elapsed_csecs64;
>  	unsigned int elapsed_csecs;
> +	bool wakeup = false;
>  
>  	do_gettimeofday(&start);
>  
> @@ -63,6 +65,10 @@ static int try_to_freeze_tasks(bool sig_only)
>  				todo++;
>  		} while_each_thread(g, p);
>  		read_unlock(&tasklist_lock);
> +		if (todo && suspend_is_blocked()) {
> +			wakeup = true;
> +			break;
> +		}
>  		if (!todo || time_after(jiffies, end_time))
>  			break;
>  
> @@ -85,13 +91,15 @@ static int try_to_freeze_tasks(bool sig_only)
>  		 * but it cleans up leftover PF_FREEZE requests.
>  		 */
>  		printk("\n");
> -		printk(KERN_ERR "Freezing of tasks failed after %d.%02d seconds "
> +		printk(KERN_ERR "Freezing of tasks %s after %d.%02d seconds "
>  				"(%d tasks refusing to freeze):\n",
> +				wakeup ? "aborted" : "failed",
>  				elapsed_csecs / 100, elapsed_csecs % 100, todo);
>  		read_lock(&tasklist_lock);
>  		do_each_thread(g, p) {
>  			task_lock(p);
> -			if (freezing(p) && !freezer_should_skip(p))
> +			if (freezing(p) && !freezer_should_skip(p)
> +					&& elapsed_csecs > 100)
>  				sched_show_task(p);
>  			cancel_freezing(p);
>  			task_unlock(p);

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH 6/8] PM: Add suspend blocking work.

[Pavel Machek]

Hi!

> Allow work to be queued that will block suspend while it is pending
> or executing. To get the same functionality in the calling code often
> requires a separate suspend_blocker for pending and executing work, or
> additional state and locking. This implementation does add additional
> state and locking, but this can be removed later if we add support for
> suspend blocking work to the core workqueue code.
> 
> Signed-off-by: Arve Hj??nnev??g <arve@android.com>

Seems sane. ACK.

> +struct suspend_blocking_work {
> +	struct work_struct work;
> +#ifdef CONFIG_OPPORTUNISTIC_SUSPEND

Cound we name it C_AUTO_SUSPEND... to reduce length and typo
potential?

> +	struct suspend_blocker suspend_blocker;
> +	work_func_t func;
> +	spinlock_t lock;
> +	int active;

Is the lock internal-use, or is API user allowed to use it?
								Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH 1/8] PM: Add suspend block api.

[Pavel Machek]

Hi!

> Adds /sys/power/policy that selects the behaviour of /sys/power/state.
> After setting the policy to opportunistic, writes to /sys/power/state
> become non-blocking requests that specify which suspend state to enter
> when no suspend blockers are active. A special state, "on", stops the
> process by activating the "main" suspend blocker.

I really don't like how this changes semantics of 'state'. I guess I'd
prefer leaving state as is -- forced transition to hibernation while
system is set to opportunistically suspend seems sane -- and adding
something like

/sys/power/autosleep

with 'off' or 'suspend' values?


> 
> Signed-off-by: Arve Hj??nnev??g <arve@android.com>
> ---
>  Documentation/power/opportunistic-suspend.txt |  114 +++++++++++
>  include/linux/suspend_blocker.h               |   64 ++++++
>  kernel/power/Kconfig                          |   16 ++
>  kernel/power/Makefile                         |    1 +
>  kernel/power/main.c                           |   89 ++++++++-
>  kernel/power/power.h                          |    5 +
>  kernel/power/suspend.c                        |    4 +-
>  kernel/power/suspend_blocker.c                |  269 +++++++++++++++++++++++++
>  8 files changed, 556 insertions(+), 6 deletions(-)
>  create mode 100644 Documentation/power/opportunistic-suspend.txt
>  create mode 100755 include/linux/suspend_blocker.h
>  create mode 100644 kernel/power/suspend_blocker.c
> 
> diff --git a/Documentation/power/opportunistic-suspend.txt b/Documentation/power/opportunistic-suspend.txt
> new file mode 100644
> index 0000000..1a29d10
> --- /dev/null
> +++ b/Documentation/power/opportunistic-suspend.txt
> @@ -0,0 +1,114 @@
> +Opportunistic Suspend
> +=====================
> +
> +Opportunistic suspend is a feature allowing the system to be suspended (ie. put
> +into one of the available sleep states) automatically whenever it is regarded
> +as idle.  The suspend blockers framework described below is used to determine
> +when that happens.
> +
> +The /sys/power/policy sysfs attribute is used to switch the system between the
> +opportunistic and "forced" suspend behavior, where in the latter case the
> +system is only suspended if a specific value, corresponding to one of the
> +available system sleep states, is written into /sys/power/state.  However, in
> +the former, opportunistic, case the system is put into the sleep state
> +corresponding to the value written to /sys/power/state whenever there are no
> +active suspend blockers. The default policy is "forced". Also, suspend blockers
> +do not affect sleep states entered from idle.
> +
> +When the policy is "opportunisic", there is a special value, "on", that can be
> +written to /sys/power/state. This will block the automatic sleep request, as if
> +a suspend blocker was used by a device driver. This way the opportunistic
> +suspend may be blocked by user space whithout switching back to the "forced"
> +mode.
> +
> +A suspend blocker is an object used to inform the PM subsystem when the system
> +can or cannot be suspended in the "opportunistic" mode (the "forced" mode
> +ignores suspend blockers).  To use it, a device driver creates a struct
> +suspend_blocker that must be initialized with suspend_blocker_init(). Before
> +freeing the suspend_blocker structure or its name, suspend_blocker_destroy()
> +must be called on it.
> +
> +A suspend blocker is activated using suspend_block(), which prevents the PM
> +subsystem from putting the system into the requested sleep state in the
> +"opportunistic" mode until the suspend blocker is deactivated with
> +suspend_unblock(). Multiple suspend blockers may be active simultaneously, and
> +the system will not suspend as long as at least one of them is active.
> +
> +If opportunistic suspend is already in progress when suspend_block() is called,
> +it will abort the suspend, unless suspend_ops->enter has already been
> +executed. If suspend is aborted this way, the system is usually not fully
> +operational at that point. The suspend callbacks of some drivers may still be
> +running and it usually takes time to restore the system to the fully operational
> +state.
> +
> +For example, in cell phones or other embedded systems, where powering the screen
> +is a significant drain on the battery, suspend blockers can be used to allow
> +user-space to decide whether a keystroke received while the system is suspended
> +should cause the screen to be turned back on or allow the system to go back into
> +suspend. Use set_irq_wake or a platform specific api to make sure the keypad
> +interrupt wakes up the cpu. Once the keypad driver has resumed, the sequence of
> +events can look like this:
> +
> +- The Keypad driver gets an interrupt. It then calls suspend_block on the
> +  keypad-scan suspend_blocker and starts scanning the keypad matrix.
> +- The keypad-scan code detects a key change and reports it to the input-event
> +  driver.
> +- The input-event driver sees the key change, enqueues an event, and calls
> +  suspend_block on the input-event-queue suspend_blocker.
> +- The keypad-scan code detects that no keys are held and calls suspend_unblock
> +  on the keypad-scan suspend_blocker.
> +- The user-space input-event thread returns from select/poll, calls
> +  suspend_block on the process-input-events suspend_blocker and then calls read
> +  on the input-event device.
> +- The input-event driver dequeues the key-event and, since the queue is now
> +  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
> +- The user-space input-event thread returns from read. If it determines that
> +  the key should leave the screen off, it calls suspend_unblock on the
> +  process_input_events suspend_blocker and then calls select or poll. The
> +  system will automatically suspend again, since now no suspend blockers are
> +  active.
> +
> +                 Key pressed   Key released
> +                     |             |
> +keypad-scan          ++++++++++++++++++
> +input-event-queue        +++          +++
> +process-input-events       +++          +++
> +
> +
> +Driver API
> +==========
> +
> +A driver can use the suspend block api by adding a suspend_blocker variable to
> +its state and calling suspend_blocker_init. For instance:
> +struct state {
> +	struct suspend_blocker suspend_blocker;
> +}
> +
> +init() {
> +	suspend_blocker_init(&state->suspend_blocker, "suspend-blocker-name");
> +}
> +
> +Before freeing the memory, suspend_blocker_destroy must be called:
> +
> +uninit() {
> +	suspend_blocker_destroy(&state->suspend_blocker);
> +}
> +
> +When the driver determines that it needs to run (usually in an interrupt
> +handler) it calls suspend_block:
> +	suspend_block(&state->suspend_blocker);
> +
> +When it no longer needs to run it calls suspend_unblock:
> +	suspend_unblock(&state->suspend_blocker);
> +
> +Calling suspend_block when the suspend blocker is active or suspend_unblock when
> +it is not active has no effect (i.e., these functions don't nest). This allows
> +drivers to update their state and call suspend suspend_block or suspend_unblock
> +based on the result.
> +For instance:
> +
> +if (list_empty(&state->pending_work))
> +	suspend_unblock(&state->suspend_blocker);
> +else
> +	suspend_block(&state->suspend_blocker);
> +
> diff --git a/include/linux/suspend_blocker.h b/include/linux/suspend_blocker.h
> new file mode 100755
> index 0000000..f9928cc
> --- /dev/null
> +++ b/include/linux/suspend_blocker.h
> @@ -0,0 +1,64 @@
> +/* include/linux/suspend_blocker.h
> + *
> + * Copyright (C) 2007-2009 Google, Inc.
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#ifndef _LINUX_SUSPEND_BLOCKER_H
> +#define _LINUX_SUSPEND_BLOCKER_H
> +
> +#include <linux/list.h>
> +
> +/**
> + * struct suspend_blocker - the basic suspend_blocker structure
> + * @link:	List entry for active or inactive list.
> + * @flags:	Tracks initialized and active state.
> + * @name:	Name used for debugging.
> + *
> + * When a suspend_blocker is active it prevents the system from entering
> + * opportunistic suspend.
> + *
> + * The suspend_blocker structure must be initialized by suspend_blocker_init()
> + */
> +
> +struct suspend_blocker {
> +#ifdef CONFIG_OPPORTUNISTIC_SUSPEND
> +	struct list_head    link;
> +	int                 flags;
> +	const char         *name;
> +#endif
> +};
> +
> +#ifdef CONFIG_OPPORTUNISTIC_SUSPEND
> +
> +void suspend_blocker_init(struct suspend_blocker *blocker, const char *name);
> +void suspend_blocker_destroy(struct suspend_blocker *blocker);
> +void suspend_block(struct suspend_blocker *blocker);
> +void suspend_unblock(struct suspend_blocker *blocker);
> +bool suspend_blocker_is_active(struct suspend_blocker *blocker);
> +bool suspend_is_blocked(void);
> +
> +#else
> +
> +static inline void suspend_blocker_init(struct suspend_blocker *blocker,
> +					const char *name) {}
> +static inline void suspend_blocker_destroy(struct suspend_blocker *blocker) {}
> +static inline void suspend_block(struct suspend_blocker *blocker) {}
> +static inline void suspend_unblock(struct suspend_blocker *blocker) {}
> +static inline bool suspend_blocker_is_active(struct suspend_blocker *bl)
> +								{ return 0; }
> +static inline bool suspend_is_blocked(void) { return 0; }
> +
> +#endif
> +
> +#endif
> +
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index 5c36ea9..55a06a1 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -130,6 +130,22 @@ config SUSPEND_FREEZER
>  
>  	  Turning OFF this setting is NOT recommended! If in doubt, say Y.
>  
> +config OPPORTUNISTIC_SUSPEND
> +	bool "Suspend blockers"
> +	depends on PM_SLEEP
> +	select RTC_LIB
> +	default n
> +	---help---
> +	  Opportunistic sleep support.  Allows the system to be put into a sleep
> +	  state opportunistically, if it doesn't do any useful work at the
> +	  moment. The PM subsystem is switched into this mode of operation by
> +	  writing "opportunistic" into /sys/power/policy, while writing
> +	  "forced" to this file turns the opportunistic suspend feature off.
> +	  In the "opportunistic" mode suspend blockers are used to determine
> +	  when to suspend the system and the value written to /sys/power/state
> +	  determines the sleep state the system will be put into when there are
> +	  no active suspend blockers.
> +
>  config HIBERNATION_NVS
>  	bool
>  
> diff --git a/kernel/power/Makefile b/kernel/power/Makefile
> index 4319181..ee5276d 100644
> --- a/kernel/power/Makefile
> +++ b/kernel/power/Makefile
> @@ -7,6 +7,7 @@ obj-$(CONFIG_PM)		+= main.o
>  obj-$(CONFIG_PM_SLEEP)		+= console.o
>  obj-$(CONFIG_FREEZER)		+= process.o
>  obj-$(CONFIG_SUSPEND)		+= suspend.o
> +obj-$(CONFIG_OPPORTUNISTIC_SUSPEND)	+= suspend_blocker.o
>  obj-$(CONFIG_PM_TEST_SUSPEND)	+= suspend_test.o
>  obj-$(CONFIG_HIBERNATION)	+= hibernate.o snapshot.o swap.o user.o
>  obj-$(CONFIG_HIBERNATION_NVS)	+= hibernate_nvs.o
> diff --git a/kernel/power/main.c b/kernel/power/main.c
> index b58800b..5f0af6c 100644
> --- a/kernel/power/main.c
> +++ b/kernel/power/main.c
> @@ -12,6 +12,7 @@
>  #include <linux/string.h>
>  #include <linux/resume-trace.h>
>  #include <linux/workqueue.h>
> +#include <linux/suspend_blocker.h>
>  
>  #include "power.h"
>  
> @@ -20,6 +21,27 @@ DEFINE_MUTEX(pm_mutex);
>  unsigned int pm_flags;
>  EXPORT_SYMBOL(pm_flags);
>  
> +struct policy {
> +	const char *name;
> +	bool (*valid_state)(suspend_state_t state);
> +	int (*set_state)(suspend_state_t state);
> +};
> +static struct policy policies[] = {
> +	{
> +		.name		= "forced",
> +		.valid_state	= valid_state,
> +		.set_state	= enter_state,
> +	},
> +#ifdef CONFIG_OPPORTUNISTIC_SUSPEND
> +	{
> +		.name		= "opportunistic",
> +		.valid_state	= request_suspend_valid_state,
> +		.set_state	= request_suspend_state,
> +	},
> +#endif
> +};
> +static int policy;
> +
>  #ifdef CONFIG_PM_SLEEP
>  
>  /* Routines for PM-transition notifications */
> @@ -146,6 +168,12 @@ struct kobject *power_kobj;
>   *
>   *	store() accepts one of those strings, translates it into the 
>   *	proper enumerated value, and initiates a suspend transition.
> + *
> + *	If policy is set to opportunistic, store() does not block until the
> + *	system resumes, and it will try to re-enter the state until another
> + *	state is requested. Suspend blockers are respected and the requested
> + *	state will only be entered when no suspend blockers are active.
> + *	Write "on" to cancel.
>   */
>  static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
>  			  char *buf)
> @@ -155,12 +183,13 @@ static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
>  	int i;
>  
>  	for (i = 0; i < PM_SUSPEND_MAX; i++) {
> -		if (pm_states[i] && valid_state(i))
> +		if (pm_states[i] && policies[policy].valid_state(i))
>  			s += sprintf(s,"%s ", pm_states[i]);
>  	}
>  #endif
>  #ifdef CONFIG_HIBERNATION
> -	s += sprintf(s, "%s\n", "disk");
> +	if (!policy)
> +		s += sprintf(s, "%s\n", "disk");
>  #else
>  	if (s != buf)
>  		/* convert the last space to a newline */
> @@ -173,7 +202,7 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  			   const char *buf, size_t n)
>  {
>  #ifdef CONFIG_SUSPEND
> -	suspend_state_t state = PM_SUSPEND_STANDBY;
> +	suspend_state_t state = PM_SUSPEND_ON;
>  	const char * const *s;
>  #endif
>  	char *p;
> @@ -184,7 +213,7 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  	len = p ? p - buf : n;
>  
>  	/* First, check if we are requested to hibernate */
> -	if (len == 4 && !strncmp(buf, "disk", len)) {
> +	if (len == 4 && !strncmp(buf, "disk", len) && !policy) {
>  		error = hibernate();
>    goto Exit;
>  	}
> @@ -195,7 +224,7 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  			break;
>  	}
>  	if (state < PM_SUSPEND_MAX && *s)
> -		error = enter_state(state);
> +		error = policies[policy].set_state(state);
>  #endif
>  
>   Exit:
> @@ -204,6 +233,55 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  
>  power_attr(state);
>  
> +/**
> + *	policy - set policy for state
> + */
> +
> +static ssize_t policy_show(struct kobject *kobj,
> +			   struct kobj_attribute *attr, char *buf)
> +{
> +	char *s = buf;
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(policies); i++) {
> +		if (i == policy)
> +			s += sprintf(s, "[%s] ", policies[i].name);
> +		else
> +			s += sprintf(s, "%s ", policies[i].name);
> +	}
> +	if (s != buf)
> +		/* convert the last space to a newline */
> +		*(s-1) = '\n';
> +	return (s - buf);
> +}
> +
> +static ssize_t policy_store(struct kobject *kobj,
> +			    struct kobj_attribute *attr,
> +			    const char *buf, size_t n)
> +{
> +	const char *s;
> +	char *p;
> +	int len;
> +	int i;
> +
> +	p = memchr(buf, '\n', n);
> +	len = p ? p - buf : n;
> +
> +	for (i = 0; i < ARRAY_SIZE(policies); i++) {
> +		s = policies[i].name;
> +		if (s && len == strlen(s) && !strncmp(buf, s, len)) {
> +			mutex_lock(&pm_mutex);
> +			policies[policy].set_state(PM_SUSPEND_ON);
> +			policy = i;
> +			mutex_unlock(&pm_mutex);
> +			return n;
> +		}
> +	}
> +	return -EINVAL;
> +}
> +
> +power_attr(policy);
> +
>  #ifdef CONFIG_PM_TRACE
>  int pm_trace_enabled;
>  
> @@ -231,6 +309,7 @@ power_attr(pm_trace);
>  
>  static struct attribute * g[] = {
>  	&state_attr.attr,
> +	&policy_attr.attr,
>  #ifdef CONFIG_PM_TRACE
>  	&pm_trace_attr.attr,
>  #endif
> diff --git a/kernel/power/power.h b/kernel/power/power.h
> index 46c5a26..9b468d7 100644
> --- a/kernel/power/power.h
> +++ b/kernel/power/power.h
> @@ -236,3 +236,8 @@ static inline void suspend_thaw_processes(void)
>  {
>  }
>  #endif
> +
> +/* kernel/power/suspend_block.c */
> +extern int request_suspend_state(suspend_state_t state);
> +extern bool request_suspend_valid_state(suspend_state_t state);
> +
> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
> index 56e7dbb..dc42006 100644
> --- a/kernel/power/suspend.c
> +++ b/kernel/power/suspend.c
> @@ -16,10 +16,12 @@
>  #include <linux/cpu.h>
>  #include <linux/syscalls.h>
>  #include <linux/gfp.h>
> +#include <linux/suspend_blocker.h>
>  
>  #include "power.h"
>  
>  const char *const pm_states[PM_SUSPEND_MAX] = {
> +	[PM_SUSPEND_ON]		= "on",
>  	[PM_SUSPEND_STANDBY]	= "standby",
>  	[PM_SUSPEND_MEM]	= "mem",
>  };
> @@ -157,7 +159,7 @@ static int suspend_enter(suspend_state_t state)
>  
>  	error = sysdev_suspend(PMSG_SUSPEND);
>  	if (!error) {
> -		if (!suspend_test(TEST_CORE))
> +		if (!suspend_is_blocked() && !suspend_test(TEST_CORE))
>  			error = suspend_ops->enter(state);
>  		sysdev_resume();
>  	}
> diff --git a/kernel/power/suspend_blocker.c b/kernel/power/suspend_blocker.c
> new file mode 100644
> index 0000000..9459361
> --- /dev/null
> +++ b/kernel/power/suspend_blocker.c
> @@ -0,0 +1,269 @@
> +/* kernel/power/suspend_blocker.c
> + *
> + * Copyright (C) 2005-2010 Google, Inc.
> + *
> + * This software is licensed under the terms of the GNU General Public
> + * License version 2, as published by the Free Software Foundation, and
> + * may be copied, distributed, and modified under those terms.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <linux/rtc.h>
> +#include <linux/suspend.h>
> +#include <linux/suspend_blocker.h>
> +#include "power.h"
> +
> +enum {
> +	DEBUG_EXIT_SUSPEND = 1U << 0,
> +	DEBUG_WAKEUP = 1U << 1,
> +	DEBUG_USER_STATE = 1U << 2,
> +	DEBUG_SUSPEND = 1U << 3,
> +	DEBUG_SUSPEND_BLOCKER = 1U << 4,
> +};
> +static int debug_mask = DEBUG_EXIT_SUSPEND | DEBUG_WAKEUP | DEBUG_USER_STATE;
> +module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
> +
> +#define SB_INITIALIZED            (1U << 8)
> +#define SB_ACTIVE                 (1U << 9)
> +
> +static DEFINE_SPINLOCK(list_lock);
> +static DEFINE_SPINLOCK(state_lock);
> +static LIST_HEAD(inactive_blockers);
> +static LIST_HEAD(active_blockers);
> +static int current_event_num;
> +struct workqueue_struct *suspend_work_queue;
> +struct suspend_blocker main_suspend_blocker;
> +static suspend_state_t requested_suspend_state = PM_SUSPEND_MEM;
> +static bool enable_suspend_blockers;
> +
> +#define pr_info_time(fmt, args...) \
> +	do { \
> +		struct timespec ts; \
> +		struct rtc_time tm; \
> +		getnstimeofday(&ts); \
> +		rtc_time_to_tm(ts.tv_sec, &tm); \
> +		pr_info(fmt "(%d-%02d-%02d %02d:%02d:%02d.%09lu UTC)\n" , \
> +			args, \
> +			tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, \
> +			tm.tm_hour, tm.tm_min, tm.tm_sec, ts.tv_nsec); \
> +	} while (0);
> +
> +static void print_active_blockers_locked(void)
> +{
> +	struct suspend_blocker *blocker;
> +
> +	list_for_each_entry(blocker, &active_blockers, link)
> +		pr_info("active suspend blocker %s\n", blocker->name);
> +}
> +
> +/**
> + * suspend_is_blocked() - Check if suspend should be blocked
> + *
> + * suspend_is_blocked can be used by generic power management code to abort
> + * suspend.
> + *
> + * To preserve backward compatibility suspend_is_blocked returns 0 unless it
> + * is called during suspend initiated from the suspend_block code.
> + */
> +bool suspend_is_blocked(void)
> +{
> +	if (!enable_suspend_blockers)
> +		return 0;
> +	return !list_empty(&active_blockers);
> +}
> +
> +static void suspend_worker(struct work_struct *work)
> +{
> +	int ret;
> +	int entry_event_num;
> +
> +	enable_suspend_blockers = true;
> +	while (!suspend_is_blocked()) {
> +		entry_event_num = current_event_num;
> +
> +		if (debug_mask & DEBUG_SUSPEND)
> +			pr_info("suspend: enter suspend\n");
> +
> +		ret = pm_suspend(requested_suspend_state);
> +
> +		if (debug_mask & DEBUG_EXIT_SUSPEND)
> +			pr_info_time("suspend: exit suspend, ret = %d ", ret);
> +
> +		if (current_event_num == entry_event_num)
> +			pr_info("suspend: pm_suspend returned with no event\n");
> +	}
> +	enable_suspend_blockers = false;
> +}
> +static DECLARE_WORK(suspend_work, suspend_worker);
> +
> +/**
> + * suspend_blocker_init() - Initialize a suspend blocker
> + * @blocker:	The suspend blocker to initialize.
> + * @name:	The name of the suspend blocker to show in debug messages.
> + *
> + * The suspend blocker struct and name must not be freed before calling
> + * suspend_blocker_destroy.
> + */
> +void suspend_blocker_init(struct suspend_blocker *blocker, const char *name)
> +{
> +	unsigned long irqflags = 0;
> +
> +	WARN_ON(!name);
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_blocker_init name=%s\n", name);
> +
> +	blocker->name = name;
> +	blocker->flags = SB_INITIALIZED;
> +	INIT_LIST_HEAD(&blocker->link);
> +
> +	spin_lock_irqsave(&list_lock, irqflags);
> +	list_add(&blocker->link, &inactive_blockers);
> +	spin_unlock_irqrestore(&list_lock, irqflags);
> +}
> +EXPORT_SYMBOL(suspend_blocker_init);
> +
> +/**
> + * suspend_blocker_destroy() - Destroy a suspend blocker
> + * @blocker:	The suspend blocker to destroy.
> + */
> +void suspend_blocker_destroy(struct suspend_blocker *blocker)
> +{
> +	unsigned long irqflags;
> +	if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
> +		return;
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_blocker_destroy name=%s\n", blocker->name);
> +
> +	spin_lock_irqsave(&list_lock, irqflags);
> +	blocker->flags &= ~SB_INITIALIZED;
> +	list_del(&blocker->link);
> +	if ((blocker->flags & SB_ACTIVE) && list_empty(&active_blockers))
> +		queue_work(suspend_work_queue, &suspend_work);
> +	spin_unlock_irqrestore(&list_lock, irqflags);
> +}
> +EXPORT_SYMBOL(suspend_blocker_destroy);
> +
> +/**
> + * suspend_block() - Block suspend
> + * @blocker:	The suspend blocker to use
> + *
> + * It is safe to call this function from interrupt context.
> + */
> +void suspend_block(struct suspend_blocker *blocker)
> +{
> +	unsigned long irqflags;
> +
> +	if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
> +		return;
> +
> +	spin_lock_irqsave(&list_lock, irqflags);
> +	blocker->flags |= SB_ACTIVE;
> +	list_del(&blocker->link);
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_block: %s\n", blocker->name);
> +
> +	list_add(&blocker->link, &active_blockers);
> +
> +	current_event_num++;
> +	spin_unlock_irqrestore(&list_lock, irqflags);
> +}
> +EXPORT_SYMBOL(suspend_block);
> +
> +/**
> + * suspend_unblock() - Unblock suspend
> + * @blocker:	The suspend blocker to unblock.
> + *
> + * If no other suspend blockers block suspend, the system will suspend.
> + *
> + * It is safe to call this function from interrupt context.
> + */
> +void suspend_unblock(struct suspend_blocker *blocker)
> +{
> +	unsigned long irqflags;
> +
> +	if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
> +		return;
> +
> +	spin_lock_irqsave(&list_lock, irqflags);
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_unblock: %s\n", blocker->name);
> +
> +	list_del(&blocker->link);
> +	list_add(&blocker->link, &inactive_blockers);
> +
> +	if ((blocker->flags & SB_ACTIVE) && list_empty(&active_blockers))
> +		queue_work(suspend_work_queue, &suspend_work);
> +	blocker->flags &= ~(SB_ACTIVE);
> +	if (blocker == &main_suspend_blocker) {
> +		if (debug_mask & DEBUG_SUSPEND)
> +			print_active_blockers_locked();
> +	}
> +	spin_unlock_irqrestore(&list_lock, irqflags);
> +}
> +EXPORT_SYMBOL(suspend_unblock);
> +
> +/**
> + * suspend_blocker_is_active() - Test if a suspend blocker is blocking suspend
> + * @blocker:	The suspend blocker to check.
> + *
> + * Returns true if the suspend_blocker is currently active.
> + */
> +bool suspend_blocker_is_active(struct suspend_blocker *blocker)
> +{
> +	WARN_ON(!(blocker->flags & SB_INITIALIZED));
> +
> +	return !!(blocker->flags & SB_ACTIVE);
> +}
> +EXPORT_SYMBOL(suspend_blocker_is_active);
> +
> +bool request_suspend_valid_state(suspend_state_t state)
> +{
> +	return (state == PM_SUSPEND_ON) || valid_state(state);
> +}
> +
> +int request_suspend_state(suspend_state_t state)
> +{
> +	unsigned long irqflags;
> +
> +	if (!request_suspend_valid_state(state))
> +		return -ENODEV;
> +
> +	spin_lock_irqsave(&state_lock, irqflags);
> +
> +	if (debug_mask & DEBUG_USER_STATE)
> +		pr_info_time("request_suspend_state: %s (%d->%d) at %lld ",
> +			     state != PM_SUSPEND_ON ? "sleep" : "wakeup",
> +			     requested_suspend_state, state,
> +			     ktime_to_ns(ktime_get()));
> +
> +	requested_suspend_state = state;
> +	if (state == PM_SUSPEND_ON)
> +		suspend_block(&main_suspend_blocker);
> +	else
> +		suspend_unblock(&main_suspend_blocker);
> +	spin_unlock_irqrestore(&state_lock, irqflags);
> +	return 0;
> +}
> +
> +static int __init suspend_block_init(void)
> +{
> +	suspend_work_queue = create_singlethread_workqueue("suspend");
> +	if (!suspend_work_queue)
> +		return -ENOMEM;
> +
> +	suspend_blocker_init(&main_suspend_blocker, "main");
> +	suspend_block(&main_suspend_blocker);
> +	return 0;
> +}
> +
> +core_initcall(suspend_block_init);

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH 6/8] PM: Add suspend blocking work.

[Tejun Heo]

Hello,

> +static void suspend_blocking_work_complete(struct suspend_blocking_work *work)
> +{
> +	unsigned long flags;
> +
> +	WARN_ON(!work->active);
> +	spin_lock_irqsave(&work->lock, flags);
> +	if (!--work->active)
> +		suspend_unblock(&work->suspend_blocker);
> +	spin_unlock_irqrestore(&work->lock, flags);
> +}

Maybe work->active can be an atomic_t and the lock can be removed?

> +/**
> + * suspend_blocking_work_destroy - Destroy suspend_blocking_work
> + * @work: The work item in question
> + *
> + * If the work was ever queued on more then one workqueue all but the last
> + * workqueue must be flushed before calling suspend_blocking_work_destroy.

As it's calling cancel_work_sync(), the above is not true.  As long as
no one is trying to queue it again, suspend_blocking_work_destroy() is
safe to call regardless of how the work has been used.

> +void suspend_blocking_work_destroy(struct suspend_blocking_work *work)
> +{
> +	cancel_suspend_blocking_work_sync(work);
> +	WARN_ON(work->active);
> +	suspend_blocker_destroy(&work->suspend_blocker);
> +}
> +EXPORT_SYMBOL(suspend_blocking_work_destroy);

Other than the above, it looks good to me.

Thanks.

-- 
tejun

Re: [PATCH 6/8] PM: Add suspend blocking work.

[Arve Hjønnevåg]

2010/4/27 Tejun Heo <tj@kernel.org>:
> Hello,
>
>> +static void suspend_blocking_work_complete(struct suspend_blocking_work *work)
>> +{
>> +     unsigned long flags;
>> +
>> +     WARN_ON(!work->active);
>> +     spin_lock_irqsave(&work->lock, flags);
>> +     if (!--work->active)
>> +             suspend_unblock(&work->suspend_blocker);
>> +     spin_unlock_irqrestore(&work->lock, flags);
>> +}
>
> Maybe work->active can be an atomic_t and the lock can be removed?
>

I need the spinlock to prevent the work from getting re-queued before
suspend_unblock.

>> +/**
>> + * suspend_blocking_work_destroy - Destroy suspend_blocking_work
>> + * @work: The work item in question
>> + *
>> + * If the work was ever queued on more then one workqueue all but the last
>> + * workqueue must be flushed before calling suspend_blocking_work_destroy.
>
> As it's calling cancel_work_sync(), the above is not true.  As long as
> no one is trying to queue it again, suspend_blocking_work_destroy() is
> safe to call regardless of how the work has been used.
>

I'm not sure what the best terminology is here, but cancel_work_sync()
only waits for work running on all the cpu-workqueues of the last
workqueue. So, if the caller queued the work on more than one
workqueue, suspend_blocking_work_destroy does not ensure that the
suspend_blocking_work structure is not still in use (it should trigger
the WARN_ON though).

>> +void suspend_blocking_work_destroy(struct suspend_blocking_work *work)
>> +{
>> +     cancel_suspend_blocking_work_sync(work);
>> +     WARN_ON(work->active);
>> +     suspend_blocker_destroy(&work->suspend_blocker);
>> +}
>> +EXPORT_SYMBOL(suspend_blocking_work_destroy);
>
> Other than the above, it looks good to me.
>
> Thanks.
>
> --
> tejun
>



-- 
Arve Hjønnevåg

Re: [PATCH 6/8] PM: Add suspend blocking work.

[Tejun Heo]

Hello,

On 04/28/2010 09:02 AM, Arve Hjønnevåg wrote:
>> Maybe work->active can be an atomic_t and the lock can be removed?
> 
> I need the spinlock to prevent the work from getting re-queued before
> suspend_unblock.

OIC.

> I'm not sure what the best terminology is here, but cancel_work_sync()
> only waits for work running on all the cpu-workqueues of the last
> workqueue. So, if the caller queued the work on more than one
> workqueue, suspend_blocking_work_destroy does not ensure that the
> suspend_blocking_work structure is not still in use (it should trigger
> the WARN_ON though).

Right, I was thinking about different cpu_workqueues and yeah, the
terminology gets pretty confusing.

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

Re: [PATCH 1/8] PM: Add suspend block api.

[Alan Stern]

On Tue, 27 Apr 2010, [UTF-8] Arve Hjønnevåg wrote:

> +For example, in cell phones or other embedded systems, where powering the screen
> +is a significant drain on the battery, suspend blockers can be used to allow
> +user-space to decide whether a keystroke received while the system is suspended
> +should cause the screen to be turned back on or allow the system to go back into
> +suspend. Use set_irq_wake or a platform specific api to make sure the keypad
> +interrupt wakes up the cpu. Once the keypad driver has resumed, the sequence of
> +events can look like this:
> +
> +- The Keypad driver gets an interrupt. It then calls suspend_block on the
> +  keypad-scan suspend_blocker and starts scanning the keypad matrix.
> +- The keypad-scan code detects a key change and reports it to the input-event
> +  driver.
> +- The input-event driver sees the key change, enqueues an event, and calls
> +  suspend_block on the input-event-queue suspend_blocker.
> +- The keypad-scan code detects that no keys are held and calls suspend_unblock
> +  on the keypad-scan suspend_blocker.
> +- The user-space input-event thread returns from select/poll, calls
> +  suspend_block on the process-input-events suspend_blocker and then calls read
> +  on the input-event device.
> +- The input-event driver dequeues the key-event and, since the queue is now
> +  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
> +- The user-space input-event thread returns from read. If it determines that
> +  the key should leave the screen off, it calls suspend_unblock on the
> +  process_input_events suspend_blocker and then calls select or poll. The
> +  system will automatically suspend again, since now no suspend blockers are
> +  active.
> +
> +                 Key pressed   Key released
> +                     |             |
> +keypad-scan          ++++++++++++++++++
> +input-event-queue        +++          +++
> +process-input-events       +++          +++

This is better than before, but it still isn't ideal.  Here's what I 
mean:

>  suspend blockers can be used to allow
> +user-space to decide whether a keystroke received while the system is suspended
> +should cause the screen to be turned back on or allow the system to go back into
> +suspend.

That's not right.  Handling the screen doesn't need suspend blockers:
The program decides what to do and then either turns on the screen or
else writes "mem" to /sys/power/state.  What suspend blockers add is
the ability to resolve races and satisfy multiple constraints when
going into suspend -- which has nothing to do with operating the
screen.

I _think_ what you're trying to get at can be expressed this way:

	Here's an example showing how a cell phone or other embedded
	system can handle keystrokes (or other input events) in the 
	presence of suspend blockers.  Use set_irq_wake...

	...

      - The user-space input-event thread returns from read.  It 
	carries out whatever activities are appropriate (for example,
	powering up the display screen, running other programs, and so 
	on).  When it is finished, it calls suspend_unblock on the
	process_input_events suspend_blocker and then calls select or
	poll.  The system will automatically suspend again when it is
	idle and no suspend blockers remain active.


> +/**
> + * suspend_block() - Block suspend
> + * @blocker:	The suspend blocker to use
> + *
> + * It is safe to call this function from interrupt context.
> + */
> +void suspend_block(struct suspend_blocker *blocker)
> +{
> +	unsigned long irqflags;
> +
> +	if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
> +		return;
> +
> +	spin_lock_irqsave(&list_lock, irqflags);
> +	blocker->flags |= SB_ACTIVE;
> +	list_del(&blocker->link);
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_block: %s\n", blocker->name);
> +
> +	list_add(&blocker->link, &active_blockers);

Here and in suspend_unblock(), you can use list_move() in place of 
list_del() followed by list_add().

Alan Stern

Re: [PATCH 6/8] PM: Add suspend blocking work.

[Oleg Nesterov]

On 04/27, Arve Hjønnevåg wrote:
>
> Allow work to be queued that will block suspend while it is pending
> or executing. To get the same functionality in the calling code often
> requires a separate suspend_blocker for pending and executing work, or
> additional state and locking. This implementation does add additional
> state and locking, but this can be removed later if we add support for
> suspend blocking work to the core workqueue code.

I think this patch is fine.

Just one silly question,

> +int queue_suspend_blocking_work(struct workqueue_struct *wq,
> +				struct suspend_blocking_work *work)
> +{
> +	int ret;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&work->lock, flags);
> +	suspend_block(&work->suspend_blocker);
> +	ret = queue_work(wq, &work->work);
> +	if (ret)
> +		work->active++;

why not

	ret = queue_work(wq, &work->work);
	if (ret) {
		suspend_block(&work->suspend_blocker);
		work->active++;
	}

?

Afaics, we can't race with work->func() doing unblock, we hold work-lock.
And this way the code looks more clear.

Sorry, I had no chance to read the previous patches. After the quick look
at 1/8 I think it is OK to call suspend_block() twice, but still...

Or I missed something? Just curious.


Hmm... actually, queue_work() can also fail if we race with cancel_ which
temporary sets WORK_STRUCT_PENDING. In that case suspend_block() won't
be paired by unblock ?


> +int schedule_suspend_blocking_work(struct suspend_blocking_work *work)
> +{
> ...
> +	ret = schedule_work(&work->work);

Off-topic. We should probably export keventd_wq to avoid the duplications
like this.

Oleg.

Re: [PATCH 6/8] PM: Add suspend blocking work.

[Tejun Heo]

On 04/28/2010 09:40 PM, Oleg Nesterov wrote:
>> +int schedule_suspend_blocking_work(struct suspend_blocking_work *work)
>> +{
>> ...
>> +	ret = schedule_work(&work->work);
> 
> Off-topic. We should probably export keventd_wq to avoid the duplications
> like this.

Yeah, had about the same thought.  cmwq exports it so I didn't suggest
it at this point but then again we don't really know whether or when
that series is going in so it might be a good idea to make that change
now.  Hmm...

Thanks.

-- 
tejun

Re: [PATCH 1/8] PM: Add suspend block api.

[Rafael J. Wysocki]

On Wednesday 28 April 2010, Arve Hjønnevåg wrote:
> Adds /sys/power/policy that selects the behaviour of /sys/power/state.
> After setting the policy to opportunistic, writes to /sys/power/state
> become non-blocking requests that specify which suspend state to enter
> when no suspend blockers are active. A special state, "on", stops the
> process by activating the "main" suspend blocker.
> 
> Signed-off-by: Arve Hjønnevåg <arve@android.com>
> ---
...
> @@ -20,6 +21,27 @@ DEFINE_MUTEX(pm_mutex);
>  unsigned int pm_flags;
>  EXPORT_SYMBOL(pm_flags);
>  
> +struct policy {
> +	const char *name;
> +	bool (*valid_state)(suspend_state_t state);
> +	int (*set_state)(suspend_state_t state);
> +};
> +static struct policy policies[] = {
> +	{
> +		.name		= "forced",
> +		.valid_state	= valid_state,
> +		.set_state	= enter_state,
> +	},
> +#ifdef CONFIG_OPPORTUNISTIC_SUSPEND
> +	{
> +		.name		= "opportunistic",
> +		.valid_state	= request_suspend_valid_state,
> +		.set_state	= request_suspend_state,
> +	},
> +#endif
> +};
> +static int policy;
> +
>  #ifdef CONFIG_PM_SLEEP
>  
>  /* Routines for PM-transition notifications */
> @@ -146,6 +168,12 @@ struct kobject *power_kobj;
>   *
>   *	store() accepts one of those strings, translates it into the 
>   *	proper enumerated value, and initiates a suspend transition.
> + *
> + *	If policy is set to opportunistic, store() does not block until the
> + *	system resumes, and it will try to re-enter the state until another
> + *	state is requested. Suspend blockers are respected and the requested
> + *	state will only be entered when no suspend blockers are active.
> + *	Write "on" to cancel.
>   */
>  static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
>  			  char *buf)
> @@ -155,12 +183,13 @@ static ssize_t state_show(struct kobject *kobj, struct kobj_attribute *attr,
>  	int i;
>  
>  	for (i = 0; i < PM_SUSPEND_MAX; i++) {
> -		if (pm_states[i] && valid_state(i))
> +		if (pm_states[i] && policies[policy].valid_state(i))
>  			s += sprintf(s,"%s ", pm_states[i]);
>  	}
>  #endif
>  #ifdef CONFIG_HIBERNATION
> -	s += sprintf(s, "%s\n", "disk");
> +	if (!policy)
> +		s += sprintf(s, "%s\n", "disk");
>  #else
>  	if (s != buf)
>  		/* convert the last space to a newline */
> @@ -173,7 +202,7 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  			   const char *buf, size_t n)
>  {
>  #ifdef CONFIG_SUSPEND
> -	suspend_state_t state = PM_SUSPEND_STANDBY;
> +	suspend_state_t state = PM_SUSPEND_ON;
>  	const char * const *s;
>  #endif
>  	char *p;
> @@ -184,7 +213,7 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  	len = p ? p - buf : n;
>  
>  	/* First, check if we are requested to hibernate */
> -	if (len == 4 && !strncmp(buf, "disk", len)) {
> +	if (len == 4 && !strncmp(buf, "disk", len) && !policy) {
>  		error = hibernate();
>    goto Exit;
>  	}
> @@ -195,7 +224,7 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  			break;
>  	}
>  	if (state < PM_SUSPEND_MAX && *s)
> -		error = enter_state(state);
> +		error = policies[policy].set_state(state);
>  #endif
>  
>   Exit:
> @@ -204,6 +233,55 @@ static ssize_t state_store(struct kobject *kobj, struct kobj_attribute *attr,
>  
>  power_attr(state);
>  
> +/**
> + *	policy - set policy for state
> + */
> +
> +static ssize_t policy_show(struct kobject *kobj,
> +			   struct kobj_attribute *attr, char *buf)
> +{
> +	char *s = buf;
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(policies); i++) {
> +		if (i == policy)
> +			s += sprintf(s, "[%s] ", policies[i].name);
> +		else
> +			s += sprintf(s, "%s ", policies[i].name);
> +	}
> +	if (s != buf)
> +		/* convert the last space to a newline */
> +		*(s-1) = '\n';
> +	return (s - buf);
> +}
> +
> +static ssize_t policy_store(struct kobject *kobj,
> +			    struct kobj_attribute *attr,
> +			    const char *buf, size_t n)
> +{
> +	const char *s;
> +	char *p;
> +	int len;
> +	int i;
> +
> +	p = memchr(buf, '\n', n);
> +	len = p ? p - buf : n;
> +
> +	for (i = 0; i < ARRAY_SIZE(policies); i++) {
> +		s = policies[i].name;
> +		if (s && len == strlen(s) && !strncmp(buf, s, len)) {
> +			mutex_lock(&pm_mutex);
> +			policies[policy].set_state(PM_SUSPEND_ON);
> +			policy = i;
> +			mutex_unlock(&pm_mutex);
> +			return n;
> +		}
> +	}
> +	return -EINVAL;
> +}
> +
> +power_attr(policy);
> +
>  #ifdef CONFIG_PM_TRACE
>  int pm_trace_enabled;
>  

Would you mind if I changed the above so that "policy" doesn't even show up
if CONFIG_OPPORTUNISTIC_SUSPEND is unset?

...
> +static void suspend_worker(struct work_struct *work)
> +{
> +	int ret;
> +	int entry_event_num;
> +
> +	enable_suspend_blockers = true;
> +	while (!suspend_is_blocked()) {
> +		entry_event_num = current_event_num;
> +
> +		if (debug_mask & DEBUG_SUSPEND)
> +			pr_info("suspend: enter suspend\n");
> +
> +		ret = pm_suspend(requested_suspend_state);
> +
> +		if (debug_mask & DEBUG_EXIT_SUSPEND)
> +			pr_info_time("suspend: exit suspend, ret = %d ", ret);
> +
> +		if (current_event_num == entry_event_num)
> +			pr_info("suspend: pm_suspend returned with no event\n");

Hmm, what exactly is this for?  It looks like a debug thing to me.  I'd use
pr_debug() here and in both debug printk()s above.  Would you agree?

> +	}
> +	enable_suspend_blockers = false;
> +}
> +static DECLARE_WORK(suspend_work, suspend_worker);
> +
> +/**
> + * suspend_blocker_init() - Initialize a suspend blocker
> + * @blocker:	The suspend blocker to initialize.
> + * @name:	The name of the suspend blocker to show in debug messages.
> + *
> + * The suspend blocker struct and name must not be freed before calling
> + * suspend_blocker_destroy.
> + */
> +void suspend_blocker_init(struct suspend_blocker *blocker, const char *name)
> +{
> +	unsigned long irqflags = 0;
> +
> +	WARN_ON(!name);
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_blocker_init name=%s\n", name);
> +
> +	blocker->name = name;
> +	blocker->flags = SB_INITIALIZED;
> +	INIT_LIST_HEAD(&blocker->link);
> +
> +	spin_lock_irqsave(&list_lock, irqflags);
> +	list_add(&blocker->link, &inactive_blockers);
> +	spin_unlock_irqrestore(&list_lock, irqflags);
> +}
> +EXPORT_SYMBOL(suspend_blocker_init);

Is there a strong objection to changing that (and the other instances below) to
EXPORT_SYMBOL_GPL?

> +
> +/**
> + * suspend_blocker_destroy() - Destroy a suspend blocker
> + * @blocker:	The suspend blocker to destroy.
> + */
> +void suspend_blocker_destroy(struct suspend_blocker *blocker)
> +{
> +	unsigned long irqflags;
> +	if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
> +		return;
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_blocker_destroy name=%s\n", blocker->name);
> +
> +	spin_lock_irqsave(&list_lock, irqflags);
> +	blocker->flags &= ~SB_INITIALIZED;
> +	list_del(&blocker->link);
> +	if ((blocker->flags & SB_ACTIVE) && list_empty(&active_blockers))
> +		queue_work(suspend_work_queue, &suspend_work);
> +	spin_unlock_irqrestore(&list_lock, irqflags);
> +}
> +EXPORT_SYMBOL(suspend_blocker_destroy);
> +
> +/**
> + * suspend_block() - Block suspend
> + * @blocker:	The suspend blocker to use
> + *
> + * It is safe to call this function from interrupt context.
> + */
> +void suspend_block(struct suspend_blocker *blocker)
> +{
> +	unsigned long irqflags;
> +
> +	if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
> +		return;
> +
> +	spin_lock_irqsave(&list_lock, irqflags);
> +	blocker->flags |= SB_ACTIVE;
> +	list_del(&blocker->link);
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_block: %s\n", blocker->name);
> +
> +	list_add(&blocker->link, &active_blockers);
> +
> +	current_event_num++;
> +	spin_unlock_irqrestore(&list_lock, irqflags);
> +}
> +EXPORT_SYMBOL(suspend_block);
> +
> +/**
> + * suspend_unblock() - Unblock suspend
> + * @blocker:	The suspend blocker to unblock.
> + *
> + * If no other suspend blockers block suspend, the system will suspend.
> + *
> + * It is safe to call this function from interrupt context.
> + */
> +void suspend_unblock(struct suspend_blocker *blocker)
> +{
> +	unsigned long irqflags;
> +
> +	if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
> +		return;
> +
> +	spin_lock_irqsave(&list_lock, irqflags);
> +
> +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> +		pr_info("suspend_unblock: %s\n", blocker->name);
> +
> +	list_del(&blocker->link);
> +	list_add(&blocker->link, &inactive_blockers);
> +
> +	if ((blocker->flags & SB_ACTIVE) && list_empty(&active_blockers))
> +		queue_work(suspend_work_queue, &suspend_work);
> +	blocker->flags &= ~(SB_ACTIVE);
> +	if (blocker == &main_suspend_blocker) {
> +		if (debug_mask & DEBUG_SUSPEND)
> +			print_active_blockers_locked();
> +	}
> +	spin_unlock_irqrestore(&list_lock, irqflags);
> +}
> +EXPORT_SYMBOL(suspend_unblock);
> +
> +/**
> + * suspend_blocker_is_active() - Test if a suspend blocker is blocking suspend
> + * @blocker:	The suspend blocker to check.
> + *
> + * Returns true if the suspend_blocker is currently active.
> + */
> +bool suspend_blocker_is_active(struct suspend_blocker *blocker)
> +{
> +	WARN_ON(!(blocker->flags & SB_INITIALIZED));
> +
> +	return !!(blocker->flags & SB_ACTIVE);
> +}
> +EXPORT_SYMBOL(suspend_blocker_is_active);
> +
> +bool request_suspend_valid_state(suspend_state_t state)
> +{
> +	return (state == PM_SUSPEND_ON) || valid_state(state);
> +}
> +
> +int request_suspend_state(suspend_state_t state)
> +{
> +	unsigned long irqflags;
> +
> +	if (!request_suspend_valid_state(state))
> +		return -ENODEV;
> +
> +	spin_lock_irqsave(&state_lock, irqflags);
> +
> +	if (debug_mask & DEBUG_USER_STATE)
> +		pr_info_time("request_suspend_state: %s (%d->%d) at %lld ",
> +			     state != PM_SUSPEND_ON ? "sleep" : "wakeup",
> +			     requested_suspend_state, state,
> +			     ktime_to_ns(ktime_get()));
> +
> +	requested_suspend_state = state;
> +	if (state == PM_SUSPEND_ON)
> +		suspend_block(&main_suspend_blocker);
> +	else
> +		suspend_unblock(&main_suspend_blocker);
> +	spin_unlock_irqrestore(&state_lock, irqflags);
> +	return 0;
> +}

I think the two functions above should be static, shouldn't they?

> +static int __init suspend_block_init(void)
> +{
> +	suspend_work_queue = create_singlethread_workqueue("suspend");
> +	if (!suspend_work_queue)
> +		return -ENOMEM;
> +
> +	suspend_blocker_init(&main_suspend_blocker, "main");
> +	suspend_block(&main_suspend_blocker);
> +	return 0;
> +}
> +
> +core_initcall(suspend_block_init);

Hmm.  Why don't you want to put that initialization into pm_init() (in
kernel/power/main.c)?

Also, we already have one PM workqueue.  It is used for runtime PM, but I guess
it may be used just as well for the opportunistic suspend.  It is freezable,
but would it hurt?

Rafael

Re: [PATCH 2/8] PM: suspend_block: Add driver to access suspend blockers from user-space

[Rafael J. Wysocki]

On Wednesday 28 April 2010, Arve Hjønnevåg wrote:
> Add a misc device, "suspend_blocker", that allows user-space processes
> to block auto suspend. The device has ioctls to create a suspend_blocker,
> and to block and unblock suspend. To delete the suspend_blocker, close
> the device.
> 
> Signed-off-by: Arve Hjønnevåg <arve@android.com>
...
> +
> +#include <linux/fs.h>
> +#include <linux/miscdevice.h>
> +#include <linux/module.h>
> +#include <linux/uaccess.h>
> +#include <linux/slab.h>
> +#include <linux/suspend_blocker.h>
> +#include <linux/suspend_block_dev.h>
> +
> +enum {
> +	DEBUG_FAILURE	= BIT(0),
> +};
> +static int debug_mask = DEBUG_FAILURE;

What's the exact purpose of this?

> +module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
> +
> +static DEFINE_MUTEX(ioctl_lock);
> +
> +struct user_suspend_blocker {
> +	struct suspend_blocker	blocker;
> +	char			name[0];
> +};

Why is this not in a header?

Rafael

Re: [PATCH 6/8] PM: Add suspend blocking work.

[Rafael J. Wysocki]

On Wednesday 28 April 2010, Tejun Heo wrote:
> On 04/28/2010 09:40 PM, Oleg Nesterov wrote:
> >> +int schedule_suspend_blocking_work(struct suspend_blocking_work *work)
> >> +{
> >> ...
> >> +	ret = schedule_work(&work->work);
> > 
> > Off-topic. We should probably export keventd_wq to avoid the duplications
> > like this.
> 
> Yeah, had about the same thought.  cmwq exports it so I didn't suggest
> it at this point but then again we don't really know whether or when
> that series is going in

As soon as there are no major objections.  At least to my tree.

> so it might be a good idea to make that change now.  Hmm...

I'd rather like a follow-up patch changing that, if poss.

Thanks,
Rafael

Re: [PATCH 6/8] PM: Add suspend blocking work.

[Rafael J. Wysocki]

On Wednesday 28 April 2010, Oleg Nesterov wrote:
> On 04/27, Arve Hjønnevåg wrote:
> >
> > Allow work to be queued that will block suspend while it is pending
> > or executing. To get the same functionality in the calling code often
> > requires a separate suspend_blocker for pending and executing work, or
> > additional state and locking. This implementation does add additional
> > state and locking, but this can be removed later if we add support for
> > suspend blocking work to the core workqueue code.
> 
> I think this patch is fine.
> 
> Just one silly question,
> 
> > +int queue_suspend_blocking_work(struct workqueue_struct *wq,
> > +				struct suspend_blocking_work *work)
> > +{
> > +	int ret;
> > +	unsigned long flags;
> > +
> > +	spin_lock_irqsave(&work->lock, flags);
> > +	suspend_block(&work->suspend_blocker);
> > +	ret = queue_work(wq, &work->work);
> > +	if (ret)
> > +		work->active++;
> 
> why not
> 
> 	ret = queue_work(wq, &work->work);
> 	if (ret) {
> 		suspend_block(&work->suspend_blocker);
> 		work->active++;
> 	}
> 
> ?
> 
> Afaics, we can't race with work->func() doing unblock, we hold work-lock.
> And this way the code looks more clear.

Agreed.  Arve, any objections to doing that?

> Sorry, I had no chance to read the previous patches. After the quick look
> at 1/8 I think it is OK to call suspend_block() twice, but still...

It is.

> Or I missed something? Just curious.
> 
> 
> Hmm... actually, queue_work() can also fail if we race with cancel_ which
> temporary sets WORK_STRUCT_PENDING. In that case suspend_block() won't
> be paired by unblock ?
> 
> 
> > +int schedule_suspend_blocking_work(struct suspend_blocking_work *work)
> > +{
> > ...
> > +	ret = schedule_work(&work->work);
> 
> Off-topic. We should probably export keventd_wq to avoid the duplications
> like this.

Please see my reply to Tejun. :-)

Rafael

Re: [PATCH 1/8] PM: Add suspend block api.

[Rafael J. Wysocki]

On Wednesday 28 April 2010, Alan Stern wrote:
> On Tue, 27 Apr 2010, [UTF-8] Arve Hjønnevåg wrote:
> 
> > +For example, in cell phones or other embedded systems, where powering the screen
> > +is a significant drain on the battery, suspend blockers can be used to allow
> > +user-space to decide whether a keystroke received while the system is suspended
> > +should cause the screen to be turned back on or allow the system to go back into
> > +suspend. Use set_irq_wake or a platform specific api to make sure the keypad
> > +interrupt wakes up the cpu. Once the keypad driver has resumed, the sequence of
> > +events can look like this:
> > +
> > +- The Keypad driver gets an interrupt. It then calls suspend_block on the
> > +  keypad-scan suspend_blocker and starts scanning the keypad matrix.
> > +- The keypad-scan code detects a key change and reports it to the input-event
> > +  driver.
> > +- The input-event driver sees the key change, enqueues an event, and calls
> > +  suspend_block on the input-event-queue suspend_blocker.
> > +- The keypad-scan code detects that no keys are held and calls suspend_unblock
> > +  on the keypad-scan suspend_blocker.
> > +- The user-space input-event thread returns from select/poll, calls
> > +  suspend_block on the process-input-events suspend_blocker and then calls read
> > +  on the input-event device.
> > +- The input-event driver dequeues the key-event and, since the queue is now
> > +  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
> > +- The user-space input-event thread returns from read. If it determines that
> > +  the key should leave the screen off, it calls suspend_unblock on the
> > +  process_input_events suspend_blocker and then calls select or poll. The
> > +  system will automatically suspend again, since now no suspend blockers are
> > +  active.
> > +
> > +                 Key pressed   Key released
> > +                     |             |
> > +keypad-scan          ++++++++++++++++++
> > +input-event-queue        +++          +++
> > +process-input-events       +++          +++
> 
> This is better than before, but it still isn't ideal.  Here's what I 
> mean:
> 
> >  suspend blockers can be used to allow
> > +user-space to decide whether a keystroke received while the system is suspended
> > +should cause the screen to be turned back on or allow the system to go back into
> > +suspend.
> 
> That's not right.  Handling the screen doesn't need suspend blockers:
> The program decides what to do and then either turns on the screen or
> else writes "mem" to /sys/power/state.  What suspend blockers add is
> the ability to resolve races and satisfy multiple constraints when
> going into suspend -- which has nothing to do with operating the
> screen.
> 
> I _think_ what you're trying to get at can be expressed this way:
> 
> 	Here's an example showing how a cell phone or other embedded
> 	system can handle keystrokes (or other input events) in the 
> 	presence of suspend blockers.  Use set_irq_wake...
> 
> 	...
> 
>       - The user-space input-event thread returns from read.  It 
> 	carries out whatever activities are appropriate (for example,
> 	powering up the display screen, running other programs, and so 
> 	on).  When it is finished, it calls suspend_unblock on the
> 	process_input_events suspend_blocker and then calls select or
> 	poll.  The system will automatically suspend again when it is
> 	idle and no suspend blockers remain active.

Yeah, that sounds better.  Arve, what do you think?

> > +/**
> > + * suspend_block() - Block suspend
> > + * @blocker:	The suspend blocker to use
> > + *
> > + * It is safe to call this function from interrupt context.
> > + */
> > +void suspend_block(struct suspend_blocker *blocker)
> > +{
> > +	unsigned long irqflags;
> > +
> > +	if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
> > +		return;
> > +
> > +	spin_lock_irqsave(&list_lock, irqflags);
> > +	blocker->flags |= SB_ACTIVE;
> > +	list_del(&blocker->link);
> > +
> > +	if (debug_mask & DEBUG_SUSPEND_BLOCKER)
> > +		pr_info("suspend_block: %s\n", blocker->name);
> > +
> > +	list_add(&blocker->link, &active_blockers);
> 
> Here and in suspend_unblock(), you can use list_move() in place of 
> list_del() followed by list_add().

Indeed.  And the debug statement might be moved out of the critical section IMHO.

Thanks,
Rafael

Re: [PATCH 6/8] PM: Add suspend blocking work.

[Arve Hjønnevåg]

2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
> On Wednesday 28 April 2010, Oleg Nesterov wrote:
>> On 04/27, Arve Hjønnevåg wrote:
>> >
>> > Allow work to be queued that will block suspend while it is pending
>> > or executing. To get the same functionality in the calling code often
>> > requires a separate suspend_blocker for pending and executing work, or
>> > additional state and locking. This implementation does add additional
>> > state and locking, but this can be removed later if we add support for
>> > suspend blocking work to the core workqueue code.
>>
>> I think this patch is fine.
>>
>> Just one silly question,
>>
>> > +int queue_suspend_blocking_work(struct workqueue_struct *wq,
>> > +                           struct suspend_blocking_work *work)
>> > +{
>> > +   int ret;
>> > +   unsigned long flags;
>> > +
>> > +   spin_lock_irqsave(&work->lock, flags);
>> > +   suspend_block(&work->suspend_blocker);
>> > +   ret = queue_work(wq, &work->work);
>> > +   if (ret)
>> > +           work->active++;
>>
>> why not
>>
>>       ret = queue_work(wq, &work->work);
>>       if (ret) {
>>               suspend_block(&work->suspend_blocker);
>>               work->active++;
>>       }
>>
>> ?
>>
>> Afaics, we can't race with work->func() doing unblock, we hold work-lock.
>> And this way the code looks more clear.
>
> Agreed.  Arve, any objections to doing that?
>

I need to fix the race, but I can easily fix it in
cancel_suspend_blocking_work_sync instead. If the suspend blocker is
active for a long time, and DEBUG_SUSPEND_BLOCKER is enabled, we can
tell if the work is constantly re-queued or if the workqueue is stuck.

>> Sorry, I had no chance to read the previous patches. After the quick look
>> at 1/8 I think it is OK to call suspend_block() twice, but still...
>
> It is.
>
>> Or I missed something? Just curious.
>>
>>
>> Hmm... actually, queue_work() can also fail if we race with cancel_ which
>> temporary sets WORK_STRUCT_PENDING. In that case suspend_block() won't
>> be paired by unblock ?
>>
>>
>> > +int schedule_suspend_blocking_work(struct suspend_blocking_work *work)
>> > +{
>> > ...
>> > +   ret = schedule_work(&work->work);
>>
>> Off-topic. We should probably export keventd_wq to avoid the duplications
>> like this.
>
> Please see my reply to Tejun. :-)
>
> Rafael
>



-- 
Arve Hjønnevåg

Re: [PATCH 6/8] PM: Add suspend blocking work.

[Rafael J. Wysocki]

On Thursday 29 April 2010, Arve Hjønnevåg wrote:
> 2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
> > On Wednesday 28 April 2010, Oleg Nesterov wrote:
> >> On 04/27, Arve Hjønnevåg wrote:
> >> >
> >> > Allow work to be queued that will block suspend while it is pending
> >> > or executing. To get the same functionality in the calling code often
> >> > requires a separate suspend_blocker for pending and executing work, or
> >> > additional state and locking. This implementation does add additional
> >> > state and locking, but this can be removed later if we add support for
> >> > suspend blocking work to the core workqueue code.
> >>
> >> I think this patch is fine.
> >>
> >> Just one silly question,
> >>
> >> > +int queue_suspend_blocking_work(struct workqueue_struct *wq,
> >> > +                           struct suspend_blocking_work *work)
> >> > +{
> >> > +   int ret;
> >> > +   unsigned long flags;
> >> > +
> >> > +   spin_lock_irqsave(&work->lock, flags);
> >> > +   suspend_block(&work->suspend_blocker);
> >> > +   ret = queue_work(wq, &work->work);
> >> > +   if (ret)
> >> > +           work->active++;
> >>
> >> why not
> >>
> >>       ret = queue_work(wq, &work->work);
> >>       if (ret) {
> >>               suspend_block(&work->suspend_blocker);
> >>               work->active++;
> >>       }
> >>
> >> ?
> >>
> >> Afaics, we can't race with work->func() doing unblock, we hold work-lock.
> >> And this way the code looks more clear.
> >
> > Agreed.  Arve, any objections to doing that?
> >
> 
> I need to fix the race, but I can easily fix it in
> cancel_suspend_blocking_work_sync instead. If the suspend blocker is
> active for a long time, and DEBUG_SUSPEND_BLOCKER is enabled, we can
> tell if the work is constantly re-queued or if the workqueue is stuck.

Well, perhaps that's worth adding a comment to the code.  The debug part is not
immediately visible from the code itself.

Rafael

Re: [PATCH 2/8] PM: suspend_block: Add driver to access suspend blockers from user-space

[Arve Hjønnevåg]

2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
> On Wednesday 28 April 2010, Arve Hjønnevåg wrote:
>> Add a misc device, "suspend_blocker", that allows user-space processes
>> to block auto suspend. The device has ioctls to create a suspend_blocker,
>> and to block and unblock suspend. To delete the suspend_blocker, close
>> the device.
>>
>> Signed-off-by: Arve Hjønnevåg <arve@android.com>
> ...
>> +
>> +#include <linux/fs.h>
>> +#include <linux/miscdevice.h>
>> +#include <linux/module.h>
>> +#include <linux/uaccess.h>
>> +#include <linux/slab.h>
>> +#include <linux/suspend_blocker.h>
>> +#include <linux/suspend_block_dev.h>
>> +
>> +enum {
>> +     DEBUG_FAILURE   = BIT(0),
>> +};
>> +static int debug_mask = DEBUG_FAILURE;
>
> What's the exact purpose of this?

To show errors returned to user space. I can turn it off by default if you want.

>
>> +module_param_named(debug_mask, debug_mask, int, S_IRUGO | S_IWUSR | S_IWGRP);
>> +
>> +static DEFINE_MUTEX(ioctl_lock);
>> +
>> +struct user_suspend_blocker {
>> +     struct suspend_blocker  blocker;
>> +     char                    name[0];
>> +};
>
> Why is this not in a header?

It's private to this file.

>
> Rafael
> --
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>



-- 
Arve Hjønnevåg

Re: [PATCH 2/8] PM: suspend_block: Add driver to access suspend blockers from user-space

[Rafael J. Wysocki]

On Thursday 29 April 2010, Arve Hjønnevåg wrote:
> 2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
> > On Wednesday 28 April 2010, Arve Hjønnevåg wrote:
> >> Add a misc device, "suspend_blocker", that allows user-space processes
> >> to block auto suspend. The device has ioctls to create a suspend_blocker,
> >> and to block and unblock suspend. To delete the suspend_blocker, close
> >> the device.
> >>
> >> Signed-off-by: Arve Hjønnevåg <arve@android.com>
> > ...
> >> +
> >> +#include <linux/fs.h>
> >> +#include <linux/miscdevice.h>
> >> +#include <linux/module.h>
> >> +#include <linux/uaccess.h>
> >> +#include <linux/slab.h>
> >> +#include <linux/suspend_blocker.h>
> >> +#include <linux/suspend_block_dev.h>
> >> +
> >> +enum {
> >> +     DEBUG_FAILURE   = BIT(0),
> >> +};
> >> +static int debug_mask = DEBUG_FAILURE;
> >
> > What's the exact purpose of this?
> 
> To show errors returned to user space. I can turn it off by default if you want.

Not necessarily, but why is it a mask?  It looks like a 0/1 thing would be
sufficient.

BTW, I'd put parens around (debug_mask & DEBUG_FAILURE) for clarity.

Rafael

Re: [PATCH 1/8] PM: Add suspend block api.

[Arve Hjønnevåg]

2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
> On Wednesday 28 April 2010, Alan Stern wrote:
>> On Tue, 27 Apr 2010, [UTF-8] Arve Hjønnevåg wrote:
>>
>> > +For example, in cell phones or other embedded systems, where powering the screen
>> > +is a significant drain on the battery, suspend blockers can be used to allow
>> > +user-space to decide whether a keystroke received while the system is suspended
>> > +should cause the screen to be turned back on or allow the system to go back into
>> > +suspend. Use set_irq_wake or a platform specific api to make sure the keypad
>> > +interrupt wakes up the cpu. Once the keypad driver has resumed, the sequence of
>> > +events can look like this:
>> > +
>> > +- The Keypad driver gets an interrupt. It then calls suspend_block on the
>> > +  keypad-scan suspend_blocker and starts scanning the keypad matrix.
>> > +- The keypad-scan code detects a key change and reports it to the input-event
>> > +  driver.
>> > +- The input-event driver sees the key change, enqueues an event, and calls
>> > +  suspend_block on the input-event-queue suspend_blocker.
>> > +- The keypad-scan code detects that no keys are held and calls suspend_unblock
>> > +  on the keypad-scan suspend_blocker.
>> > +- The user-space input-event thread returns from select/poll, calls
>> > +  suspend_block on the process-input-events suspend_blocker and then calls read
>> > +  on the input-event device.
>> > +- The input-event driver dequeues the key-event and, since the queue is now
>> > +  empty, it calls suspend_unblock on the input-event-queue suspend_blocker.
>> > +- The user-space input-event thread returns from read. If it determines that
>> > +  the key should leave the screen off, it calls suspend_unblock on the
>> > +  process_input_events suspend_blocker and then calls select or poll. The
>> > +  system will automatically suspend again, since now no suspend blockers are
>> > +  active.
>> > +
>> > +                 Key pressed   Key released
>> > +                     |             |
>> > +keypad-scan          ++++++++++++++++++
>> > +input-event-queue        +++          +++
>> > +process-input-events       +++          +++
>>
>> This is better than before, but it still isn't ideal.  Here's what I
>> mean:
>>
>> >  suspend blockers can be used to allow
>> > +user-space to decide whether a keystroke received while the system is suspended
>> > +should cause the screen to be turned back on or allow the system to go back into
>> > +suspend.
>>
>> That's not right.  Handling the screen doesn't need suspend blockers:
>> The program decides what to do and then either turns on the screen or
>> else writes "mem" to /sys/power/state.

That does not work though. Unless every key turns the screen on you
will have a race every time the user presses a key you want to ignore.

>>  What suspend blockers add is
>> the ability to resolve races and satisfy multiple constraints when
>> going into suspend -- which has nothing to do with operating the
>> screen.

I'm not sure I agree with this. You cannot reliably turn the screen on
from user space when the user presses a wakeup-key without suspend
blockers.

>>
>> I _think_ what you're trying to get at can be expressed this way:
>>
>>       Here's an example showing how a cell phone or other embedded
>>       system can handle keystrokes (or other input events) in the
>>       presence of suspend blockers.  Use set_irq_wake...

OK, but the last version was what you (Alan) suggested last year.

>>
>>       ...
>>
>>       - The user-space input-event thread returns from read.  It
>>       carries out whatever activities are appropriate (for example,
>>       powering up the display screen, running other programs, and so
>>       on).  When it is finished, it calls suspend_unblock on the
>>       process_input_events suspend_blocker and then calls select or
>>       poll.  The system will automatically suspend again when it is
>>       idle and no suspend blockers remain active.
>
> Yeah, that sounds better.  Arve, what do you think?
>

Idle is irrelevant and needs to be removed. This new last step is also
no longer a concrete example, but if you really think is it better I
can change it.

>> > +/**
>> > + * suspend_block() - Block suspend
>> > + * @blocker:       The suspend blocker to use
>> > + *
>> > + * It is safe to call this function from interrupt context.
>> > + */
>> > +void suspend_block(struct suspend_blocker *blocker)
>> > +{
>> > +   unsigned long irqflags;
>> > +
>> > +   if (WARN_ON(!(blocker->flags & SB_INITIALIZED)))
>> > +           return;
>> > +
>> > +   spin_lock_irqsave(&list_lock, irqflags);
>> > +   blocker->flags |= SB_ACTIVE;
>> > +   list_del(&blocker->link);
>> > +
>> > +   if (debug_mask & DEBUG_SUSPEND_BLOCKER)
>> > +           pr_info("suspend_block: %s\n", blocker->name);
>> > +
>> > +   list_add(&blocker->link, &active_blockers);
>>
>> Here and in suspend_unblock(), you can use list_move() in place of
>> list_del() followed by list_add().
>

OK.

> Indeed.  And the debug statement might be moved out of the critical section IMHO.
>

If I move the debug statements out of the critical section you could
end entering suspend while the debug log claims a suspend blocker was
active, but I can move the debug statement to the start of the
critical section.

-- 
Arve Hjønnevåg

Re: [PATCH 2/8] PM: suspend_block: Add driver to access suspend blockers from user-space

[Arve Hjønnevåg]

2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
> On Thursday 29 April 2010, Arve Hjønnevåg wrote:
>> 2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
>> > On Wednesday 28 April 2010, Arve Hjønnevåg wrote:
>> >> Add a misc device, "suspend_blocker", that allows user-space processes
>> >> to block auto suspend. The device has ioctls to create a suspend_blocker,
>> >> and to block and unblock suspend. To delete the suspend_blocker, close
>> >> the device.
>> >>
>> >> Signed-off-by: Arve Hjønnevåg <arve@android.com>
>> > ...
>> >> +
>> >> +#include <linux/fs.h>
>> >> +#include <linux/miscdevice.h>
>> >> +#include <linux/module.h>
>> >> +#include <linux/uaccess.h>
>> >> +#include <linux/slab.h>
>> >> +#include <linux/suspend_blocker.h>
>> >> +#include <linux/suspend_block_dev.h>
>> >> +
>> >> +enum {
>> >> +     DEBUG_FAILURE   = BIT(0),
>> >> +};
>> >> +static int debug_mask = DEBUG_FAILURE;
>> >
>> > What's the exact purpose of this?
>>
>> To show errors returned to user space. I can turn it off by default if you want.
>
> Not necessarily, but why is it a mask?  It looks like a 0/1 thing would be
> sufficient.

I may want to add a bit to print all user-space block and unblock calls.

>
> BTW, I'd put parens around (debug_mask & DEBUG_FAILURE) for clarity.

OK.

-- 
Arve Hjønnevåg

Re: [PATCH 1/8] PM: Add suspend block api.

[Arve Hjønnevåg]

2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
...
>>
>> +/**
>> + *   policy - set policy for state
>> + */
>> +
>> +static ssize_t policy_show(struct kobject *kobj,
>> +                        struct kobj_attribute *attr, char *buf)
>> +{
>> +     char *s = buf;
>> +     int i;
>> +
>> +     for (i = 0; i < ARRAY_SIZE(policies); i++) {
>> +             if (i == policy)
>> +                     s += sprintf(s, "[%s] ", policies[i].name);
>> +             else
>> +                     s += sprintf(s, "%s ", policies[i].name);
>> +     }
>> +     if (s != buf)
>> +             /* convert the last space to a newline */
>> +             *(s-1) = '\n';
>> +     return (s - buf);
>> +}
>> +
>> +static ssize_t policy_store(struct kobject *kobj,
>> +                         struct kobj_attribute *attr,
>> +                         const char *buf, size_t n)
>> +{
>> +     const char *s;
>> +     char *p;
>> +     int len;
>> +     int i;
>> +
>> +     p = memchr(buf, '\n', n);
>> +     len = p ? p - buf : n;
>> +
>> +     for (i = 0; i < ARRAY_SIZE(policies); i++) {
>> +             s = policies[i].name;
>> +             if (s && len == strlen(s) && !strncmp(buf, s, len)) {
>> +                     mutex_lock(&pm_mutex);
>> +                     policies[policy].set_state(PM_SUSPEND_ON);
>> +                     policy = i;
>> +                     mutex_unlock(&pm_mutex);
>> +                     return n;
>> +             }
>> +     }
>> +     return -EINVAL;
>> +}
>> +
>> +power_attr(policy);
>> +
>>  #ifdef CONFIG_PM_TRACE
>>  int pm_trace_enabled;
>>
>
> Would you mind if I changed the above so that "policy" doesn't even show up
> if CONFIG_OPPORTUNISTIC_SUSPEND is unset?
>
I don't mind, but It did not seem worth the trouble to hide it. It
will only list the supported policies, and it is easy to add or remove
policies this way.

> ...
>> +static void suspend_worker(struct work_struct *work)
>> +{
>> +     int ret;
>> +     int entry_event_num;
>> +
>> +     enable_suspend_blockers = true;
>> +     while (!suspend_is_blocked()) {
>> +             entry_event_num = current_event_num;
>> +
>> +             if (debug_mask & DEBUG_SUSPEND)
>> +                     pr_info("suspend: enter suspend\n");
>> +
>> +             ret = pm_suspend(requested_suspend_state);
>> +
>> +             if (debug_mask & DEBUG_EXIT_SUSPEND)
>> +                     pr_info_time("suspend: exit suspend, ret = %d ", ret);
>> +
>> +             if (current_event_num == entry_event_num)
>> +                     pr_info("suspend: pm_suspend returned with no event\n");
>
> Hmm, what exactly is this for?  It looks like a debug thing to me.  I'd use
> pr_debug() here and in both debug printk()s above.  Would you agree?
>

If the driver that caused the wakeup does not use suspend blockers, we
the only choice is to try to suspend again. I want to know if this
happened. The stats patch disable this printk by default since it will
show up in the stats, and the timeout patch (not included here) delays
the retry.

...
>> +EXPORT_SYMBOL(suspend_blocker_init);
>
> Is there a strong objection to changing that (and the other instances below) to
> EXPORT_SYMBOL_GPL?
>

I don't know if it is a strong objection, but I prefer that this api
is available to all drivers. I don't want to prevent a user from using
opportunistic suspend because a non-gpl driver could not use suspend
blockers. I changed the suspend blocking work functions to be gpl only
though, since they are not required, and the workqueue api is
available to gpl code anyway.

...
>> +bool request_suspend_valid_state(suspend_state_t state)
>> +{
>> +     return (state == PM_SUSPEND_ON) || valid_state(state);
>> +}
>> +
>> +int request_suspend_state(suspend_state_t state)
>> +{
>> +     unsigned long irqflags;
>> +
>> +     if (!request_suspend_valid_state(state))
>> +             return -ENODEV;
>> +
>> +     spin_lock_irqsave(&state_lock, irqflags);
>> +
>> +     if (debug_mask & DEBUG_USER_STATE)
>> +             pr_info_time("request_suspend_state: %s (%d->%d) at %lld ",
>> +                          state != PM_SUSPEND_ON ? "sleep" : "wakeup",
>> +                          requested_suspend_state, state,
>> +                          ktime_to_ns(ktime_get()));
>> +
>> +     requested_suspend_state = state;
>> +     if (state == PM_SUSPEND_ON)
>> +             suspend_block(&main_suspend_blocker);
>> +     else
>> +             suspend_unblock(&main_suspend_blocker);
>> +     spin_unlock_irqrestore(&state_lock, irqflags);
>> +     return 0;
>> +}
>
> I think the two functions above should be static, shouldn't they?

No, they are used from main.c.

>
>> +static int __init suspend_block_init(void)
>> +{
>> +     suspend_work_queue = create_singlethread_workqueue("suspend");
>> +     if (!suspend_work_queue)
>> +             return -ENOMEM;
>> +
>> +     suspend_blocker_init(&main_suspend_blocker, "main");
>> +     suspend_block(&main_suspend_blocker);
>> +     return 0;
>> +}
>> +
>> +core_initcall(suspend_block_init);
>
> Hmm.  Why don't you want to put that initialization into pm_init() (in
> kernel/power/main.c)?

It was not needed before, but I changed pm_init to call
suspend_block_init after creating pm_wq.

>
> Also, we already have one PM workqueue.  It is used for runtime PM, but I guess
> it may be used just as well for the opportunistic suspend.  It is freezable,
> but would it hurt?

No, it works, the freezable flag is just ignored when I call
pm_suspend and I don't run anything else on the workqueue while
threads are frozen. It does need to be a single threaded workqueue
though, so make sure you don't just change that.

-- 
Arve Hjønnevåg

Re: [PATCH 6/8] PM: Add suspend blocking work.

[Arve Hjønnevåg]

2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
> On Thursday 29 April 2010, Arve Hjønnevåg wrote:
>> 2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
>> > On Wednesday 28 April 2010, Oleg Nesterov wrote:
>> >> On 04/27, Arve Hjønnevåg wrote:
>> >> >
>> >> > Allow work to be queued that will block suspend while it is pending
>> >> > or executing. To get the same functionality in the calling code often
>> >> > requires a separate suspend_blocker for pending and executing work, or
>> >> > additional state and locking. This implementation does add additional
>> >> > state and locking, but this can be removed later if we add support for
>> >> > suspend blocking work to the core workqueue code.
>> >>
>> >> I think this patch is fine.
>> >>
>> >> Just one silly question,
>> >>
>> >> > +int queue_suspend_blocking_work(struct workqueue_struct *wq,
>> >> > +                           struct suspend_blocking_work *work)
>> >> > +{
>> >> > +   int ret;
>> >> > +   unsigned long flags;
>> >> > +
>> >> > +   spin_lock_irqsave(&work->lock, flags);
>> >> > +   suspend_block(&work->suspend_blocker);
>> >> > +   ret = queue_work(wq, &work->work);
>> >> > +   if (ret)
>> >> > +           work->active++;
>> >>
>> >> why not
>> >>
>> >>       ret = queue_work(wq, &work->work);
>> >>       if (ret) {
>> >>               suspend_block(&work->suspend_blocker);
>> >>               work->active++;
>> >>       }
>> >>
>> >> ?
>> >>
>> >> Afaics, we can't race with work->func() doing unblock, we hold work-lock.
>> >> And this way the code looks more clear.
>> >
>> > Agreed.  Arve, any objections to doing that?
>> >
>>
>> I need to fix the race, but I can easily fix it in
>> cancel_suspend_blocking_work_sync instead. If the suspend blocker is
>> active for a long time, and DEBUG_SUSPEND_BLOCKER is enabled, we can
>> tell if the work is constantly re-queued or if the workqueue is stuck.
>
> Well, perhaps that's worth adding a comment to the code.  The debug part is not
> immediately visible from the code itself.

On second thought, this only makes a difference if both conditions are
true. If we are constantly re-queuing the work but it is not stuck,
either method will show the debug message, so I used Oleg's
suggestion.

-- 
Arve Hjønnevåg

Re: [PATCH 1/8] PM: Add suspend block api.

[Alan Stern]

On Wed, 28 Apr 2010, Arve Hjønnevåg wrote:

> >> >  suspend blockers can be used to allow
> >> > +user-space to decide whether a keystroke received while the system is suspended
> >> > +should cause the screen to be turned back on or allow the system to go back into
> >> > +suspend.
> >>
> >> That's not right.  Handling the screen doesn't need suspend blockers:
> >> The program decides what to do and then either turns on the screen or
> >> else writes "mem" to /sys/power/state.
> 
> That does not work though. Unless every key turns the screen on you
> will have a race every time the user presses a key you want to ignore.

Of course.  You are confirming what I wrote immediately below: Suspend
blockers help resolve races.  Note that this race has nothing to do
with the _screen_ in particular -- exactly the same race occurs if you
decide to turn on the audio speaker or some other piece of hardware.

> >>  What suspend blockers add is
> >> the ability to resolve races and satisfy multiple constraints when
> >> going into suspend -- which has nothing to do with operating the
> >> screen.
> 
> I'm not sure I agree with this. You cannot reliably turn the screen on
> from user space when the user presses a wakeup-key without suspend
> blockers.

Let's say that it has nothing to do _specifically_ with the screen.  
_Any_ action you want to take in userspace is difficult to coordinate 
with system suspends if you don't have suspend blockers.

> >>
> >> I _think_ what you're trying to get at can be expressed this way:
> >>
> >>       Here's an example showing how a cell phone or other embedded
> >>       system can handle keystrokes (or other input events) in the
> >>       presence of suspend blockers.  Use set_irq_wake...
> 
> OK, but the last version was what you (Alan) suggested last year.

So at least my mental processes have remained consistent over the span
of a year.  Nice to know I haven't undergone a complete personality 
change...  :-)

> >>       ...
> >>
> >>       - The user-space input-event thread returns from read.  It
> >>       carries out whatever activities are appropriate (for example,
> >>       powering up the display screen, running other programs, and so
> >>       on).  When it is finished, it calls suspend_unblock on the
> >>       process_input_events suspend_blocker and then calls select or
> >>       poll.  The system will automatically suspend again when it is
> >>       idle and no suspend blockers remain active.
> >
> > Yeah, that sounds better.  Arve, what do you think?
> >
> 
> Idle is irrelevant and needs to be removed. This new last step is also
> no longer a concrete example, but if you really think is it better I
> can change it.

Perhaps you would prefer to change this completely.  Write up a 
description of what can go wrong when suspend blockers _aren't_ used, 
and show how suspend blockers can prevent the problem from occurring.

But whatever you do, don't make it appear that suspend blockers allow
user programs to make decisions (which is what you wrote before).  They 
don't -- programs can make whatever decisions they want.  Suspend 
blockers merely help them carry out the actions they have decided upon 
in a safe manner.

And don't make it appear that suspend blockers can only be used for
solving screen-related problems.

Alan Stern

Re: [PATCH 6/8] PM: Add suspend blocking work.

[Oleg Nesterov]

On 04/28, Rafael J. Wysocki wrote:
>
> On Wednesday 28 April 2010, Tejun Heo wrote:
> > On 04/28/2010 09:40 PM, Oleg Nesterov wrote:
> > >> +int schedule_suspend_blocking_work(struct suspend_blocking_work *work)
> > >> +{
> > >> ...
> > >> +	ret = schedule_work(&work->work);
> > >
> > > Off-topic. We should probably export keventd_wq to avoid the duplications
> > > like this.
> >
> > Yeah, had about the same thought.  cmwq exports it so I didn't suggest
> > it at this point but then again we don't really know whether or when
> > that series is going in
>
> As soon as there are no major objections.  At least to my tree.
>
> > so it might be a good idea to make that change now.  Hmm...
>
> I'd rather like a follow-up patch changing that, if poss.

Confused. Rafael, do you mean you dislike this change now?

I don't really care, this change is trivial. But to me it makes more
sense to push the trivial/simple changes ahead. Unless they really
complicate the maintainging of the pending cmwq changes.

Hmm... Speaking about keventd_wq, I just noticed flush_delayed_work()
needs the fix:

	--- a/kernel/workqueue.c
	+++ b/kernel/workqueue.c
	@@ -774,7 +774,7 @@ void flush_delayed_work(struct delayed_w
	 {
		if (del_timer_sync(&dwork->timer)) {
			struct cpu_workqueue_struct *cwq;
	-		cwq = wq_per_cpu(keventd_wq, get_cpu());
	+		cwq = wq_per_cpu(get_wq_data(&dwork->work)->wq, get_cpu());
			__queue_work(cwq, &dwork->work);
			put_cpu();
		}

Oleg.

[PATCH 0/2] workqueue fixlets (Was: PM: Add suspend blocking work.)

[Oleg Nesterov]

On 04/29, Oleg Nesterov wrote:
>
> I don't really care, this change is trivial. But to me it makes more
> sense to push the trivial/simple changes ahead. Unless they really
> complicate the maintainging of the pending cmwq changes.
>
> Hmm... Speaking about keventd_wq, I just noticed flush_delayed_work()
> needs the fix:

So. I'd suggestd these 2 simple patches for now.

Please note that 2/2 is really trivial, it only adds EXPORT_SYMBOL but
avoids the possible cleanups to minimize the conflicts with the pending
cmwq changes. However, please feel free to ignore this patch.

As for 1/2, imho it is always better to fix the bug asap, even if it is
minor.

Oleg.

[PATCH 1/2] workqueues: flush_delayed_work: keep the original workqueue for re-queueing

[Oleg Nesterov]

flush_delayed_work() always uses keventd_wq for re-queueing,
but it should use the workqueue this dwork was queued on.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---

 kernel/workqueue.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- 34-rc1/kernel/workqueue.c~FDW_DONT_USE_KEVENT_WQ	2009-12-18 19:05:38.000000000 +0100
+++ 34-rc1/kernel/workqueue.c	2010-04-29 21:08:32.000000000 +0200
@@ -774,7 +774,7 @@ void flush_delayed_work(struct delayed_w
 {
 	if (del_timer_sync(&dwork->timer)) {
 		struct cpu_workqueue_struct *cwq;
-		cwq = wq_per_cpu(keventd_wq, get_cpu());
+		cwq = wq_per_cpu(get_wq_data(&dwork->work)->wq, get_cpu());
 		__queue_work(cwq, &dwork->work);
 		put_cpu();
 	}

[PATCH 2/2] workqueues: export keventd_wq

[Oleg Nesterov]

Export keventd_wq. Otherwise, any helper on top of queue_work() has
to be copy-and-pasted to create the version which uses keventd_wq.

Note: we can do more cleanups with this change and kill EXPORT_SYMBOLs,
almost any function which currently uses keventd_wq can become the
trivial inline.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---

 include/linux/workqueue.h |    1 +
 kernel/workqueue.c        |    3 ++-
 2 files changed, 3 insertions(+), 1 deletion(-)

--- 34-rc1/include/linux/workqueue.h~EXPORT_KEVENT_WQ	2009-12-18 19:05:38.000000000 +0100
+++ 34-rc1/include/linux/workqueue.h	2010-04-29 21:25:12.000000000 +0200
@@ -12,6 +12,7 @@
 #include <asm/atomic.h>
 
 struct workqueue_struct;
+extern struct workqueue_struct *keventd_wq;
 
 struct work_struct;
 typedef void (*work_func_t)(struct work_struct *work);
--- 34-rc1/kernel/workqueue.c~EXPORT_KEVENT_WQ	2010-04-29 21:08:32.000000000 +0200
+++ 34-rc1/kernel/workqueue.c	2010-04-29 21:23:46.000000000 +0200
@@ -717,7 +717,8 @@ int cancel_delayed_work_sync(struct dela
 }
 EXPORT_SYMBOL(cancel_delayed_work_sync);
 
-static struct workqueue_struct *keventd_wq __read_mostly;
+struct workqueue_struct *keventd_wq __read_mostly;
+EXPORT_SYMBOL(keventd_wq);
 
 /**
  * schedule_work - put work task in global workqueue

Re: [PATCH 6/8] PM: Add suspend blocking work.

[Rafael J. Wysocki]

On Thursday 29 April 2010, Oleg Nesterov wrote:
> On 04/28, Rafael J. Wysocki wrote:
> >
> > On Wednesday 28 April 2010, Tejun Heo wrote:
> > > On 04/28/2010 09:40 PM, Oleg Nesterov wrote:
> > > >> +int schedule_suspend_blocking_work(struct suspend_blocking_work *work)
> > > >> +{
> > > >> ...
> > > >> +	ret = schedule_work(&work->work);
> > > >
> > > > Off-topic. We should probably export keventd_wq to avoid the duplications
> > > > like this.
> > >
> > > Yeah, had about the same thought.  cmwq exports it so I didn't suggest
> > > it at this point but then again we don't really know whether or when
> > > that series is going in
> >
> > As soon as there are no major objections.  At least to my tree.
> >
> > > so it might be a good idea to make that change now.  Hmm...
> >
> > I'd rather like a follow-up patch changing that, if poss.
> 
> Confused. Rafael, do you mean you dislike this change now?

No, I'm fine with the change itself, but I wouldn't like to make the suspend
blockers patchset depend on something in a different tree.  If it's not the
case, I have no objections.

Rafael

Re: [PATCH 6/8] PM: Add suspend blocking work.

[Rafael J. Wysocki]

On Thursday 29 April 2010, Arve Hjønnevåg wrote:
> 2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
> > On Thursday 29 April 2010, Arve Hjønnevåg wrote:
> >> 2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
> >> > On Wednesday 28 April 2010, Oleg Nesterov wrote:
> >> >> On 04/27, Arve Hjønnevåg wrote:
> >> >> >
> >> >> > Allow work to be queued that will block suspend while it is pending
> >> >> > or executing. To get the same functionality in the calling code often
> >> >> > requires a separate suspend_blocker for pending and executing work, or
> >> >> > additional state and locking. This implementation does add additional
> >> >> > state and locking, but this can be removed later if we add support for
> >> >> > suspend blocking work to the core workqueue code.
> >> >>
> >> >> I think this patch is fine.
> >> >>
> >> >> Just one silly question,
> >> >>
> >> >> > +int queue_suspend_blocking_work(struct workqueue_struct *wq,
> >> >> > +                           struct suspend_blocking_work *work)
> >> >> > +{
> >> >> > +   int ret;
> >> >> > +   unsigned long flags;
> >> >> > +
> >> >> > +   spin_lock_irqsave(&work->lock, flags);
> >> >> > +   suspend_block(&work->suspend_blocker);
> >> >> > +   ret = queue_work(wq, &work->work);
> >> >> > +   if (ret)
> >> >> > +           work->active++;
> >> >>
> >> >> why not
> >> >>
> >> >>       ret = queue_work(wq, &work->work);
> >> >>       if (ret) {
> >> >>               suspend_block(&work->suspend_blocker);
> >> >>               work->active++;
> >> >>       }
> >> >>
> >> >> ?
> >> >>
> >> >> Afaics, we can't race with work->func() doing unblock, we hold work-lock.
> >> >> And this way the code looks more clear.
> >> >
> >> > Agreed.  Arve, any objections to doing that?
> >> >
> >>
> >> I need to fix the race, but I can easily fix it in
> >> cancel_suspend_blocking_work_sync instead. If the suspend blocker is
> >> active for a long time, and DEBUG_SUSPEND_BLOCKER is enabled, we can
> >> tell if the work is constantly re-queued or if the workqueue is stuck.
> >
> > Well, perhaps that's worth adding a comment to the code.  The debug part is not
> > immediately visible from the code itself.
> 
> On second thought, this only makes a difference if both conditions are
> true. If we are constantly re-queuing the work but it is not stuck,
> either method will show the debug message, so I used Oleg's
> suggestion.

OK, great.

Rafael

Re: [PATCH 2/8] PM: suspend_block: Add driver to access suspend blockers from user-space

[Rafael J. Wysocki]

On Thursday 29 April 2010, Arve Hjønnevåg wrote:
> 2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
> > On Thursday 29 April 2010, Arve Hjønnevåg wrote:
> >> 2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
> >> > On Wednesday 28 April 2010, Arve Hjønnevåg wrote:
> >> >> Add a misc device, "suspend_blocker", that allows user-space processes
> >> >> to block auto suspend. The device has ioctls to create a suspend_blocker,
> >> >> and to block and unblock suspend. To delete the suspend_blocker, close
> >> >> the device.
> >> >>
> >> >> Signed-off-by: Arve Hjønnevåg <arve@android.com>
> >> > ...
> >> >> +
> >> >> +#include <linux/fs.h>
> >> >> +#include <linux/miscdevice.h>
> >> >> +#include <linux/module.h>
> >> >> +#include <linux/uaccess.h>
> >> >> +#include <linux/slab.h>
> >> >> +#include <linux/suspend_blocker.h>
> >> >> +#include <linux/suspend_block_dev.h>
> >> >> +
> >> >> +enum {
> >> >> +     DEBUG_FAILURE   = BIT(0),
> >> >> +};
> >> >> +static int debug_mask = DEBUG_FAILURE;
> >> >
> >> > What's the exact purpose of this?
> >>
> >> To show errors returned to user space. I can turn it off by default if you want.
> >
> > Not necessarily, but why is it a mask?  It looks like a 0/1 thing would be
> > sufficient.
> 
> I may want to add a bit to print all user-space block and unblock calls.

Alternatively, you can add a new parameter for that, which I think I would prefer.

Rafael

Re: [PATCH 1/8] PM: Add suspend block api.

[Rafael J. Wysocki]

On Thursday 29 April 2010, Arve Hjønnevåg wrote:
> 2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
> ...
> >>
> >> +/**
> >> + *   policy - set policy for state
> >> + */
> >> +
> >> +static ssize_t policy_show(struct kobject *kobj,
> >> +                        struct kobj_attribute *attr, char *buf)
> >> +{
> >> +     char *s = buf;
> >> +     int i;
> >> +
> >> +     for (i = 0; i < ARRAY_SIZE(policies); i++) {
> >> +             if (i == policy)
> >> +                     s += sprintf(s, "[%s] ", policies[i].name);
> >> +             else
> >> +                     s += sprintf(s, "%s ", policies[i].name);
> >> +     }
> >> +     if (s != buf)
> >> +             /* convert the last space to a newline */
> >> +             *(s-1) = '\n';
> >> +     return (s - buf);
> >> +}
> >> +
> >> +static ssize_t policy_store(struct kobject *kobj,
> >> +                         struct kobj_attribute *attr,
> >> +                         const char *buf, size_t n)
> >> +{
> >> +     const char *s;
> >> +     char *p;
> >> +     int len;
> >> +     int i;
> >> +
> >> +     p = memchr(buf, '\n', n);
> >> +     len = p ? p - buf : n;
> >> +
> >> +     for (i = 0; i < ARRAY_SIZE(policies); i++) {
> >> +             s = policies[i].name;
> >> +             if (s && len == strlen(s) && !strncmp(buf, s, len)) {
> >> +                     mutex_lock(&pm_mutex);
> >> +                     policies[policy].set_state(PM_SUSPEND_ON);
> >> +                     policy = i;
> >> +                     mutex_unlock(&pm_mutex);
> >> +                     return n;
> >> +             }
> >> +     }
> >> +     return -EINVAL;
> >> +}
> >> +
> >> +power_attr(policy);
> >> +
> >>  #ifdef CONFIG_PM_TRACE
> >>  int pm_trace_enabled;
> >>
> >
> > Would you mind if I changed the above so that "policy" doesn't even show up
> > if CONFIG_OPPORTUNISTIC_SUSPEND is unset?
> >
> I don't mind, but It did not seem worth the trouble to hide it. It
> will only list the supported policies, and it is easy to add or remove
> policies this way.
> 
> > ...
> >> +static void suspend_worker(struct work_struct *work)
> >> +{
> >> +     int ret;
> >> +     int entry_event_num;
> >> +
> >> +     enable_suspend_blockers = true;
> >> +     while (!suspend_is_blocked()) {
> >> +             entry_event_num = current_event_num;
> >> +
> >> +             if (debug_mask & DEBUG_SUSPEND)
> >> +                     pr_info("suspend: enter suspend\n");
> >> +
> >> +             ret = pm_suspend(requested_suspend_state);
> >> +
> >> +             if (debug_mask & DEBUG_EXIT_SUSPEND)
> >> +                     pr_info_time("suspend: exit suspend, ret = %d ", ret);
> >> +
> >> +             if (current_event_num == entry_event_num)
> >> +                     pr_info("suspend: pm_suspend returned with no event\n");
> >
> > Hmm, what exactly is this for?  It looks like a debug thing to me.  I'd use
> > pr_debug() here and in both debug printk()s above.  Would you agree?
> >
> 
> If the driver that caused the wakeup does not use suspend blockers, we
> the only choice is to try to suspend again. I want to know if this
> happened. The stats patch disable this printk by default since it will
> show up in the stats, and the timeout patch (not included here) delays
> the retry.
> 
> ...
> >> +EXPORT_SYMBOL(suspend_blocker_init);
> >
> > Is there a strong objection to changing that (and the other instances below) to
> > EXPORT_SYMBOL_GPL?
> >
> 
> I don't know if it is a strong objection, but I prefer that this api
> is available to all drivers. I don't want to prevent a user from using
> opportunistic suspend because a non-gpl driver could not use suspend
> blockers. I changed the suspend blocking work functions to be gpl only
> though, since they are not required, and the workqueue api is
> available to gpl code anyway.
> 
> ...
> >> +bool request_suspend_valid_state(suspend_state_t state)
> >> +{
> >> +     return (state == PM_SUSPEND_ON) || valid_state(state);
> >> +}
> >> +
> >> +int request_suspend_state(suspend_state_t state)
> >> +{
> >> +     unsigned long irqflags;
> >> +
> >> +     if (!request_suspend_valid_state(state))
> >> +             return -ENODEV;
> >> +
> >> +     spin_lock_irqsave(&state_lock, irqflags);
> >> +
> >> +     if (debug_mask & DEBUG_USER_STATE)
> >> +             pr_info_time("request_suspend_state: %s (%d->%d) at %lld ",
> >> +                          state != PM_SUSPEND_ON ? "sleep" : "wakeup",
> >> +                          requested_suspend_state, state,
> >> +                          ktime_to_ns(ktime_get()));
> >> +
> >> +     requested_suspend_state = state;
> >> +     if (state == PM_SUSPEND_ON)
> >> +             suspend_block(&main_suspend_blocker);
> >> +     else
> >> +             suspend_unblock(&main_suspend_blocker);
> >> +     spin_unlock_irqrestore(&state_lock, irqflags);
> >> +     return 0;
> >> +}
> >
> > I think the two functions above should be static, shouldn't they?
> 
> No, they are used from main.c.
> 
> >
> >> +static int __init suspend_block_init(void)
> >> +{
> >> +     suspend_work_queue = create_singlethread_workqueue("suspend");
> >> +     if (!suspend_work_queue)
> >> +             return -ENOMEM;
> >> +
> >> +     suspend_blocker_init(&main_suspend_blocker, "main");
> >> +     suspend_block(&main_suspend_blocker);
> >> +     return 0;
> >> +}
> >> +
> >> +core_initcall(suspend_block_init);
> >
> > Hmm.  Why don't you want to put that initialization into pm_init() (in
> > kernel/power/main.c)?
> 
> It was not needed before, but I changed pm_init to call
> suspend_block_init after creating pm_wq.
> 
> >
> > Also, we already have one PM workqueue.  It is used for runtime PM, but I guess
> > it may be used just as well for the opportunistic suspend.  It is freezable,
> > but would it hurt?
> 
> No, it works, the freezable flag is just ignored when I call
> pm_suspend and I don't run anything else on the workqueue while
> threads are frozen. It does need to be a single threaded workqueue
> though, so make sure you don't just change that.

Freezable workqueues have to be singlethread or else there will be unfixable
races, so you can safely assume things will stay as they are in this respect.

Rafael


> 
> 

Re: [PATCH 1/8] PM: Add suspend block api.

[Arve Hjønnevåg]

2010/4/29 Alan Stern <stern@rowland.harvard.edu>:
> On Wed, 28 Apr 2010, Arve Hjønnevåg wrote:
>
>> >> >  suspend blockers can be used to allow
>> >> > +user-space to decide whether a keystroke received while the system is suspended
>> >> > +should cause the screen to be turned back on or allow the system to go back into
>> >> > +suspend.
>> >>
>> >> That's not right.  Handling the screen doesn't need suspend blockers:
>> >> The program decides what to do and then either turns on the screen or
>> >> else writes "mem" to /sys/power/state.
>>
>> That does not work though. Unless every key turns the screen on you
>> will have a race every time the user presses a key you want to ignore.
>
> Of course.  You are confirming what I wrote immediately below: Suspend
Yet you offered it as an example of why "Handling the screen doesn't
need suspend blockers".

> blockers help resolve races.  Note that this race has nothing to do
> with the _screen_ in particular -- exactly the same race occurs if you
> decide to turn on the audio speaker or some other piece of hardware.
>
I agree with this, but that does not mean that describing how you can
handle the screen with suspend blockers is a bad example.

>> >>  What suspend blockers add is
>> >> the ability to resolve races and satisfy multiple constraints when
>> >> going into suspend -- which has nothing to do with operating the
>> >> screen.
>>
>> I'm not sure I agree with this. You cannot reliably turn the screen on
>> from user space when the user presses a wakeup-key without suspend
>> blockers.
>
> Let's say that it has nothing to do _specifically_ with the screen.
> _Any_ action you want to take in userspace is difficult to coordinate
> with system suspends if you don't have suspend blockers.
>
>> >>
>> >> I _think_ what you're trying to get at can be expressed this way:
>> >>
>> >>       Here's an example showing how a cell phone or other embedded
>> >>       system can handle keystrokes (or other input events) in the
>> >>       presence of suspend blockers.  Use set_irq_wake...
>>
>> OK, but the last version was what you (Alan) suggested last year.
>
> So at least my mental processes have remained consistent over the span
> of a year.  Nice to know I haven't undergone a complete personality
> change...  :-)
>
>> >>       ...
>> >>
>> >>       - The user-space input-event thread returns from read.  It
>> >>       carries out whatever activities are appropriate (for example,
>> >>       powering up the display screen, running other programs, and so
>> >>       on).  When it is finished, it calls suspend_unblock on the
>> >>       process_input_events suspend_blocker and then calls select or
>> >>       poll.  The system will automatically suspend again when it is
>> >>       idle and no suspend blockers remain active.
>> >
>> > Yeah, that sounds better.  Arve, what do you think?
>> >
>>
>> Idle is irrelevant and needs to be removed. This new last step is also
>> no longer a concrete example, but if you really think is it better I
>> can change it.
>
> Perhaps you would prefer to change this completely.  Write up a
> description of what can go wrong when suspend blockers _aren't_ used,
> and show how suspend blockers can prevent the problem from occurring.
>
> But whatever you do, don't make it appear that suspend blockers allow
> user programs to make decisions (which is what you wrote before).  They
> don't -- programs can make whatever decisions they want.  Suspend
> blockers merely help them carry out the actions they have decided upon
> in a safe manner.

I think suspend blockers do allow user programs to make decisions.
Without suspend blockers some decisions can only be safely be made in
the kernel/drivers.

>
> And don't make it appear that suspend blockers can only be used for
> solving screen-related problems.

How about:

- The user-space input-event thread returns from read. If it
determines that the key should be ignored, it calls suspend_unblock on
the process_input_events suspend_blocker and then calls select or
poll. The system will automatically suspend again, since now no
suspend blockers are active.

If the key that was pressed instead should preform a simple action
(for example, adjusting the volume), this action can be performed
right before calling suspend_unblock on the process_input_events
suspend_blocker. However, if the key triggers a longer-running action,
that action needs its own suspend_blocker and suspend_block must be
called on that suspend blocker before calling suspend_unblock on the
process_input_events suspend_blocker.

-- 
Arve Hjønnevåg

Re: [PATCH 2/8] PM: suspend_block: Add driver to access suspend blockers from user-space

[Arve Hjønnevåg]

2010/4/29 Rafael J. Wysocki <rjw@sisk.pl>:
> On Thursday 29 April 2010, Arve Hjønnevåg wrote:
>> 2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
>> > On Thursday 29 April 2010, Arve Hjønnevåg wrote:
>> >> 2010/4/28 Rafael J. Wysocki <rjw@sisk.pl>:
>> >> > On Wednesday 28 April 2010, Arve Hjønnevåg wrote:
>> >> >> Add a misc device, "suspend_blocker", that allows user-space processes
>> >> >> to block auto suspend. The device has ioctls to create a suspend_blocker,
>> >> >> and to block and unblock suspend. To delete the suspend_blocker, close
>> >> >> the device.
>> >> >>
>> >> >> Signed-off-by: Arve Hjønnevåg <arve@android.com>
>> >> > ...
>> >> >> +
>> >> >> +#include <linux/fs.h>
>> >> >> +#include <linux/miscdevice.h>
>> >> >> +#include <linux/module.h>
>> >> >> +#include <linux/uaccess.h>
>> >> >> +#include <linux/slab.h>
>> >> >> +#include <linux/suspend_blocker.h>
>> >> >> +#include <linux/suspend_block_dev.h>
>> >> >> +
>> >> >> +enum {
>> >> >> +     DEBUG_FAILURE   = BIT(0),
>> >> >> +};
>> >> >> +static int debug_mask = DEBUG_FAILURE;
>> >> >
>> >> > What's the exact purpose of this?
>> >>
>> >> To show errors returned to user space. I can turn it off by default if you want.
>> >
>> > Not necessarily, but why is it a mask?  It looks like a 0/1 thing would be
>> > sufficient.
>>
>> I may want to add a bit to print all user-space block and unblock calls.
>
> Alternatively, you can add a new parameter for that, which I think I would prefer.
>

I use a bit-mask in the main suspend blocker code. This makes it easy
to turn on or off all the messages.

-- 
Arve Hjønnevåg

Re: [PATCH 1/8] PM: Add suspend block api.

[Tejun Heo]

Hello,

On 04/29/2010 11:16 PM, Rafael J. Wysocki wrote:
>>> Also, we already have one PM workqueue.  It is used for runtime PM, but I guess
>>> it may be used just as well for the opportunistic suspend.  It is freezable,
>>> but would it hurt?
>>
>> No, it works, the freezable flag is just ignored when I call
>> pm_suspend and I don't run anything else on the workqueue while
>> threads are frozen. It does need to be a single threaded workqueue
>> though, so make sure you don't just change that.
> 
> Freezable workqueues have to be singlethread or else there will be unfixable
> races, so you can safely assume things will stay as they are in this respect.

Rafael, can you elaborate a bit more on this?  Just in case I missed
something while doing cmwq as it currently doesn't have such limit.

Thanks.

-- 
tejun

Re: [PATCH 1/2] workqueues: flush_delayed_work: keep the original workqueue for re-queueing

[Tejun Heo]

Hello,

On 04/29/2010 09:45 PM, Oleg Nesterov wrote:
> flush_delayed_work() always uses keventd_wq for re-queueing,
> but it should use the workqueue this dwork was queued on.
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Acked-by: Tejun Heo <tj@kernel.org>

I'll queue it through the wq tree I have.

Thanks.

-- 
tejun

Re: [PATCH 2/2] workqueues: export keventd_wq

[Tejun Heo]

Hello,

On 04/29/2010 09:45 PM, Oleg Nesterov wrote:
> -static struct workqueue_struct *keventd_wq __read_mostly;
> +struct workqueue_struct *keventd_wq __read_mostly;
> +EXPORT_SYMBOL(keventd_wq);

Umm... does it have to be EXPORTed?  Suspend block API can't be built
as a module, right?

-- 
tejun

Re: [PATCH 2/2] workqueues: export keventd_wq

[Arve Hjønnevåg]

On Thu, Apr 29, 2010 at 10:16 PM, Tejun Heo <tj@kernel.org> wrote:
> Hello,
>
> On 04/29/2010 09:45 PM, Oleg Nesterov wrote:
>> -static struct workqueue_struct *keventd_wq __read_mostly;
>> +struct workqueue_struct *keventd_wq __read_mostly;
>> +EXPORT_SYMBOL(keventd_wq);
>
> Umm... does it have to be EXPORTed?  Suspend block API can't be built
> as a module, right?

The suspend block api cannot be built as a module, but if
schedule_suspend_blocking_work will just call
queue_suspend_blocking_work(keventd_wq, work) it may as well be an
inline function which would require the export.

-- 
Arve Hjønnevåg

Re: [PATCH 2/2] workqueues: export keventd_wq

[Tejun Heo]

On 04/30/2010 07:39 AM, Arve Hjønnevåg wrote:
> On Thu, Apr 29, 2010 at 10:16 PM, Tejun Heo <tj@kernel.org> wrote:
>> Hello,
>>
>> On 04/29/2010 09:45 PM, Oleg Nesterov wrote:
>>> -static struct workqueue_struct *keventd_wq __read_mostly;
>>> +struct workqueue_struct *keventd_wq __read_mostly;
>>> +EXPORT_SYMBOL(keventd_wq);
>>
>> Umm... does it have to be EXPORTed?  Suspend block API can't be built
>> as a module, right?
> 
> The suspend block api cannot be built as a module, but if
> schedule_suspend_blocking_work will just call
> queue_suspend_blocking_work(keventd_wq, work) it may as well be an
> inline function which would require the export.

I think it would be better to keep the thing inside the kernel, at
least for now.  It's not like we need to save cpu cycles spent on a
function call here (in block suspend API and in workqueue general).

Thanks.

-- 
tejun

Re: [PATCH 1/8] PM: Add suspend block api.

[Alan Stern]

On Thu, 29 Apr 2010, Arve Hjønnevåg wrote:

> >> That does not work though. Unless every key turns the screen on you
> >> will have a race every time the user presses a key you want to ignore.
> >
> > Of course.  You are confirming what I wrote immediately below: Suspend
> Yet you offered it as an example of why "Handling the screen doesn't
> need suspend blockers".

What I meant was this: Without suspend blockers you can still turn the
screen on and off, but you can't avoid races.  Therefore: You don't
need suspend blockers to handle the screen, but you do need them to
handle races.

> > blockers help resolve races.  Note that this race has nothing to do
> > with the _screen_ in particular -- exactly the same race occurs if you
> > decide to turn on the audio speaker or some other piece of hardware.
> >
> I agree with this, but that does not mean that describing how you can
> handle the screen with suspend blockers is a bad example.

Agreed; it's not a bad example.  My objection is to the way the example
is presented.

> I think suspend blockers do allow user programs to make decisions.
> Without suspend blockers some decisions can only be safely be made in
> the kernel/drivers.

This is our real disagreement -- it's mainly a question of the meaning
of words.  When one says "A allows B to make a decision", this means
that without A, B would literally be unable to decide what to do.  It
wouldn't be able to "make up its mind" (like the donkey that starves
while stuck halfway between two piles of hay because it can't decide 
which pile to eat).

That's not what you mean to say.  In your case there's no difficulty in
making the choice -- the program knows exactly what it wants to do.  
The problem is that without suspend blockers, it can't _carry out_ the
chosen action.  To put it another way, the suspend blockers don't help
with deciding which action to take; rather they help with taking the
action after it has been decided upon.

Or put this way: Suppose suspend blockers were not available.  Then the
desired action would not be safe, so the program wouldn't be able to
take it.  The decision would thus be even simpler, since one of the
choices would be eliminated.  In this way, lack of suspend blockers
makes the decision easier, not harder.  So you shouldn't say that
suspend blockers allow the program to make the decision.

What your example _really_ shows is how a program can carry out a 
prolonged action that requires the system to be awake for an extended 
period of time.  Even with suspend blockers, the right way to do this 
safely isn't necessarily obvious.  That's how the example helps.

> How about:
> 
> - The user-space input-event thread returns from read. If it
> determines that the key should be ignored, it calls suspend_unblock on
> the process_input_events suspend_blocker and then calls select or
> poll. The system will automatically suspend again, since now no
> suspend blockers are active.

Do you want to mention here that everything will work correctly even if 
the system suspends before the thread can call select or poll?

> If the key that was pressed instead should preform a simple action
> (for example, adjusting the volume), this action can be performed
> right before calling suspend_unblock on the process_input_events
> suspend_blocker. However, if the key triggers a longer-running action,
> that action needs its own suspend_blocker and suspend_block must be
> called on that suspend blocker before calling suspend_unblock on the
> process_input_events suspend_blocker.

That's good!  I like it.  Now if you can change the beginning of the
example, to say that it shows how programs should use suspend blockers
instead of showing that suspend blockers allow programs to make
decisions.

Alan Stern

Re: [PATCH 1/8] PM: Add suspend block api.

[Oleg Nesterov]

On 04/30, Tejun Heo wrote:
>
> On 04/29/2010 11:16 PM, Rafael J. Wysocki wrote:
> >>> Also, we already have one PM workqueue.  It is used for runtime PM, but I guess
> >>> it may be used just as well for the opportunistic suspend.  It is freezable,
> >>> but would it hurt?
> >>
> > Freezable workqueues have to be singlethread or else there will be unfixable
> > races, so you can safely assume things will stay as they are in this respect.
>
> Rafael, can you elaborate a bit more on this?  Just in case I missed
> something while doing cmwq as it currently doesn't have such limit.

Currently _cpu_down() can't flush and/or stop the frozen cwq->thread.

IIRC this is fixable, but needs the nasty complications. We should
thaw + stop the frozen cwq->thread, then move the pending works to
another CPU.

Oleg.

Re: [PATCH 2/2] workqueues: export keventd_wq

[Oleg Nesterov]

On 04/30, Tejun Heo wrote:
>
> On 04/30/2010 07:39 AM, Arve Hjønnevåg wrote:
> > On Thu, Apr 29, 2010 at 10:16 PM, Tejun Heo <tj@kernel.org> wrote:
> >> Hello,
> >>
> >> On 04/29/2010 09:45 PM, Oleg Nesterov wrote:
> >>> -static struct workqueue_struct *keventd_wq __read_mostly;
> >>> +struct workqueue_struct *keventd_wq __read_mostly;
> >>> +EXPORT_SYMBOL(keventd_wq);
> >>
> >> Umm... does it have to be EXPORTed?  Suspend block API can't be built
> >> as a module, right?

Right, but this allows to make schedule_xxx/flush_scheduled_work
inline and kill more EXPORT_SYMBOL's, and cmwq exports it anyway
(iirc it also renames it).

> > The suspend block api cannot be built as a module, but if
> > schedule_suspend_blocking_work will just call
> > queue_suspend_blocking_work(keventd_wq, work) it may as well be an
> > inline function which would require the export.
>
> I think it would be better to keep the thing inside the kernel, at
> least for now.

But then schedule_suspend_blocking_work() in turn needs EXPORT_SYMBOL().


OK. Let's forget this patch. We can unify schedule_suspend_blocking_work
and queue_suspend_blocking_work later, or Arve can add this export into
his patch (without EXPORT_SYMBOL) - either way I agree. This is very
minor issue, I regret I originated this almost offtopic noise ;)

Oleg.

Re: [PATCH 2/2] workqueues: export keventd_wq

[Tejun Heo]

Hello,

On 04/30/2010 08:05 PM, Oleg Nesterov wrote:
> Right, but this allows to make schedule_xxx/flush_scheduled_work
> inline and kill more EXPORT_SYMBOL's, and cmwq exports it anyway
> (iirc it also renames it).

Yeah, the 'iirc' part was why I didn't want to export it at this point. :-)

> OK. Let's forget this patch. We can unify schedule_suspend_blocking_work
> and queue_suspend_blocking_work later, or Arve can add this export into
> his patch (without EXPORT_SYMBOL) - either way I agree. This is very
> minor issue, I regret I originated this almost offtopic noise ;)

And, again, yeah, let's do it later.

Thanks.

-- 
tejun

Re: [PATCH 1/8] PM: Add suspend block api.

[Alan Stern]

On Tue, 27 Apr 2010, [UTF-8] Arve Hjønnevåg wrote:

> +static void suspend_worker(struct work_struct *work)
> +{
> +	int ret;
> +	int entry_event_num;
> +
> +	enable_suspend_blockers = true;
> +	while (!suspend_is_blocked()) {
> +		entry_event_num = current_event_num;
> +
> +		if (debug_mask & DEBUG_SUSPEND)
> +			pr_info("suspend: enter suspend\n");
> +
> +		ret = pm_suspend(requested_suspend_state);
> +
> +		if (debug_mask & DEBUG_EXIT_SUSPEND)
> +			pr_info_time("suspend: exit suspend, ret = %d ", ret);
> +
> +		if (current_event_num == entry_event_num)
> +			pr_info("suspend: pm_suspend returned with no event\n");
> +	}
> +	enable_suspend_blockers = false;
> +}

Here's a completely new issue.  When using opportunistic suspends on an
SMP system, it could happen that the system gets a wakeup event and
this routine starts running again before the event's IRQ handler has
finished (or has enabled a suspend blocker).  The system would 
re-suspend too soon.

Is there anything in the PM core that waits until all outstanding IRQs 
have been handled before unfreezing processes?  If there is, I can't 
find it.  Should such a thing be added?

Alan Stern

Re: [PATCH 1/8] PM: Add suspend block api.

[Rafael J. Wysocki]

On Thursday 06 May 2010, Alan Stern wrote:
> On Tue, 27 Apr 2010, [UTF-8] Arve Hjønnevåg wrote:
> 
> > +static void suspend_worker(struct work_struct *work)
> > +{
> > +	int ret;
> > +	int entry_event_num;
> > +
> > +	enable_suspend_blockers = true;
> > +	while (!suspend_is_blocked()) {
> > +		entry_event_num = current_event_num;
> > +
> > +		if (debug_mask & DEBUG_SUSPEND)
> > +			pr_info("suspend: enter suspend\n");
> > +
> > +		ret = pm_suspend(requested_suspend_state);
> > +
> > +		if (debug_mask & DEBUG_EXIT_SUSPEND)
> > +			pr_info_time("suspend: exit suspend, ret = %d ", ret);
> > +
> > +		if (current_event_num == entry_event_num)
> > +			pr_info("suspend: pm_suspend returned with no event\n");
> > +	}
> > +	enable_suspend_blockers = false;
> > +}
> 
> Here's a completely new issue.  When using opportunistic suspends on an
> SMP system, it could happen that the system gets a wakeup event and
> this routine starts running again before the event's IRQ handler has
> finished (or has enabled a suspend blocker).  The system would 
> re-suspend too soon.

This routine will be run from a freezable workqueue.

Rafael

Re: [PATCH 1/8] PM: Add suspend block api.

[Alan Stern]

On Thu, 6 May 2010, Rafael J. Wysocki wrote:

> > Here's a completely new issue.  When using opportunistic suspends on an
> > SMP system, it could happen that the system gets a wakeup event and
> > this routine starts running again before the event's IRQ handler has
> > finished (or has enabled a suspend blocker).  The system would 
> > re-suspend too soon.
> 
> This routine will be run from a freezable workqueue.

But how do you know that processes won't get unfrozen until all the 
pending IRQs have been handled?  Imagine something like this:

	CPU 0			CPU 1
	-----			-----
	Wake up non-boot CPUs
	Resume devices		Invoke the IRQ handler

	[ CPU 0 should wait here for the handler to finish, 
	  but it doesn't ]

	Defrost threads		Handler running...
	Workqueue routine runs
	Start another suspend
				Handler enables a suspend blocker,
				but it's too late

Alan Stern

Re: [PATCH 1/8] PM: Add suspend block api.

[Arve Hjønnevåg]

On Thu, May 6, 2010 at 12:40 PM, Alan Stern <stern@rowland.harvard.edu> wrote:
> On Thu, 6 May 2010, Rafael J. Wysocki wrote:
>
>> > Here's a completely new issue.  When using opportunistic suspends on an
>> > SMP system, it could happen that the system gets a wakeup event and
>> > this routine starts running again before the event's IRQ handler has
>> > finished (or has enabled a suspend blocker).  The system would
>> > re-suspend too soon.
>>
>> This routine will be run from a freezable workqueue.
>
> But how do you know that processes won't get unfrozen until all the
> pending IRQs have been handled?  Imagine something like this:
>
>        CPU 0                   CPU 1
>        -----                   -----
>        Wake up non-boot CPUs
>        Resume devices          Invoke the IRQ handler
>
>        [ CPU 0 should wait here for the handler to finish,
>          but it doesn't ]
>
>        Defrost threads         Handler running...
>        Workqueue routine runs
>        Start another suspend
>                                Handler enables a suspend blocker,
>                                but it's too late

It is not optimal, but it is not too late. We check if any suspend
blockers block suspend after disabling non-boot cpus so as long as
this is done in a way that does not lose interrupts the resuspend
attempt will not succeed.

-- 
Arve Hjønnevåg

Re: [PATCH 1/8] PM: Add suspend block api.

[Alan Stern]

On Thu, 6 May 2010, Arve Hjønnevåg wrote:

> On Thu, May 6, 2010 at 12:40 PM, Alan Stern <stern@rowland.harvard.edu> wrote:
> > On Thu, 6 May 2010, Rafael J. Wysocki wrote:
> >
> >> > Here's a completely new issue.  When using opportunistic suspends on an
> >> > SMP system, it could happen that the system gets a wakeup event and
> >> > this routine starts running again before the event's IRQ handler has
> >> > finished (or has enabled a suspend blocker).  The system would
> >> > re-suspend too soon.
> >>
> >> This routine will be run from a freezable workqueue.
> >
> > But how do you know that processes won't get unfrozen until all the
> > pending IRQs have been handled?  Imagine something like this:
> >
> >        CPU 0                   CPU 1
> >        -----                   -----
> >        Wake up non-boot CPUs
> >        Resume devices          Invoke the IRQ handler
> >
> >        [ CPU 0 should wait here for the handler to finish,
> >          but it doesn't ]
> >
> >        Defrost threads         Handler running...
> >        Workqueue routine runs
> >        Start another suspend
> >                                Handler enables a suspend blocker,
> >                                but it's too late
> 
> It is not optimal, but it is not too late. We check if any suspend
> blockers block suspend after disabling non-boot cpus so as long as
> this is done in a way that does not lose interrupts the resuspend
> attempt will not succeed.

Is it possible for the resuspend to disable CPU 1 before the IRQ
handler can enable its suspend blocker?  (Probably not -- but I don't
know enough about how non-boot CPUs are enabled or disabled.)

Alan Stern

Re: [PATCH 1/8] PM: Add suspend block api.

[Tejun Heo]

Hello,

(sorry about late reply)

On 04/30/2010 07:26 PM, Oleg Nesterov wrote:
> Currently _cpu_down() can't flush and/or stop the frozen cwq->thread.
> 
> IIRC this is fixable, but needs the nasty complications. We should
> thaw + stop the frozen cwq->thread, then move the pending works to
> another CPU.

Oh, this isn't an issue w/ cmwq.  While frozen all new works are
collected into per-cpu delayed worklist and while frozen trustee in
charge of the cpu will keep waiting.  Once thawed, trustee will
execute all works including the delayed ones unbound to any cpu.

Thanks.

-- 
tejun

Re: [PATCH 1/8] PM: Add suspend block api.

[Rafael J. Wysocki]

On Thursday 20 May 2010, Tejun Heo wrote:
> Hello,
> 
> (sorry about late reply)
> 
> On 04/30/2010 07:26 PM, Oleg Nesterov wrote:
> > Currently _cpu_down() can't flush and/or stop the frozen cwq->thread.
> > 
> > IIRC this is fixable, but needs the nasty complications. We should
> > thaw + stop the frozen cwq->thread, then move the pending works to
> > another CPU.
> 
> Oh, this isn't an issue w/ cmwq.  While frozen all new works are
> collected into per-cpu delayed worklist and while frozen trustee in
> charge of the cpu will keep waiting.  Once thawed, trustee will
> execute all works including the delayed ones unbound to any cpu.

So, does it require any intrusive changes to make it possible to create
multithread freezable workqueues?

Rafael

Re: [PATCH 1/8] PM: Add suspend block api.

[Tejun Heo]

Hello,

On 05/21/2010 12:27 AM, Rafael J. Wysocki wrote:
>> Oh, this isn't an issue w/ cmwq.  While frozen all new works are
>> collected into per-cpu delayed worklist and while frozen trustee in
>> charge of the cpu will keep waiting.  Once thawed, trustee will
>> execute all works including the delayed ones unbound to any cpu.
> 
> So, does it require any intrusive changes to make it possible to create
> multithread freezable workqueues?

cmwq itself is quite intrusive changes but w/ cmwq it just takes
flipping a flag when creating the queue.

Thanks.

-- 
tejun