[RFC][PATCH 7/7] PM / Sleep: Add user space interface for manipulating wakeup sources

["Rafael J. Wysocki" <rjw@sisk.pl>]

From: Rafael J. Wysocki <rjw@sisk.pl>

Android allows user space to manipulate wakelocks using two
sysfs file located in /sys/power/, wake_lock and wake_unlock.
Writing a wakelock name and optionally a timeout to the wake_lock
file causes the wakelock whose name was written to be acquired (it
is created before is necessary), optionally with the given timeout.
Writing the name of a wakelock to wake_unlock causes that wakelock
to be released.

Implement an analogous interface for user space using wakeup sources.
Add the /sys/power/wake_lock and /sys/power/wake_unlock files
allowing user space to create, activate and deactivate wakeup
sources, such that writing a name and optionally a timeout to
wake_lock causes the wakeup source of that name to be activated,
optionally with the given timeout.  If that wakeup source doesn't
exist, it will be created and then activated.  Writing a name to
wake_unlock causes the wakeup source of that name, if there is one,
to be deactivated.  Wakeup sources created with the help of
wake_lock that haven't been used for more than 5 minutes are garbage
collected and destroyed.  Moreover, there can be only WL_NUMBER_LIMIT
wakeup sources created with the help of wake_lock present at a time.

The data type used to track wakeup sources created by user space is
called "struct wakelock" to indicate the origins of this feature.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
 Documentation/ABI/testing/sysfs-power |   42 ++++++
 drivers/base/power/wakeup.c           |    1 
 kernel/power/Kconfig                  |    8 +
 kernel/power/Makefile                 |    1 
 kernel/power/main.c                   |   41 ++++++
 kernel/power/power.h                  |    9 +
 kernel/power/wakelock.c               |  218 ++++++++++++++++++++++++++++++++++
 7 files changed, 320 insertions(+)

Index: linux/kernel/power/main.c
===================================================================
--- linux.orig/kernel/power/main.c
+++ linux/kernel/power/main.c
@@ -422,6 +422,43 @@ static ssize_t autosleep_store(struct ko
 
 power_attr(autosleep);
 #endif /* CONFIG_PM_AUTOSLEEP */
+
+#ifdef CONFIG_PM_WAKELOCKS
+static ssize_t wake_lock_show(struct kobject *kobj,
+			      struct kobj_attribute *attr,
+			      char *buf)
+{
+	return pm_show_wakelocks(buf, true);
+}
+
+static ssize_t wake_lock_store(struct kobject *kobj,
+			       struct kobj_attribute *attr,
+			       const char *buf, size_t n)
+{
+	int error = pm_wake_lock(buf);
+	return error ? error : n;
+}
+
+power_attr(wake_lock);
+
+static ssize_t wake_unlock_show(struct kobject *kobj,
+				struct kobj_attribute *attr,
+				char *buf)
+{
+	return pm_show_wakelocks(buf, false);
+}
+
+static ssize_t wake_unlock_store(struct kobject *kobj,
+				 struct kobj_attribute *attr,
+				 const char *buf, size_t n)
+{
+	int error = pm_wake_unlock(buf);
+	return error ? error : n;
+}
+
+power_attr(wake_unlock);
+
+#endif /* CONFIG_PM_WAKELOCKS */
 #endif /* CONFIG_PM_SLEEP */
 
 #ifdef CONFIG_PM_TRACE
@@ -478,6 +515,10 @@ static struct attribute * g[] = {
 #ifdef CONFIG_PM_AUTOSLEEP
 	&autosleep_attr.attr,
 #endif
+#ifdef CONFIG_PM_WAKELOCKS
+	&wake_lock_attr.attr,
+	&wake_unlock_attr.attr,
+#endif
 #ifdef CONFIG_PM_DEBUG
 	&pm_test_attr.attr,
 #endif
Index: linux/kernel/power/power.h
===================================================================
--- linux.orig/kernel/power/power.h
+++ linux/kernel/power/power.h
@@ -282,3 +282,12 @@ static inline void pm_autosleep_unlock(v
 static inline suspend_state_t pm_autosleep_state(void) { return PM_SUSPEND_ON; }
 
 #endif /* !CONFIG_PM_AUTOSLEEP */
+
+#ifdef CONFIG_PM_WAKELOCKS
+
+/* kernel/power/wakelock.c */
+extern ssize_t pm_show_wakelocks(char *buf, bool show_active);
+extern int pm_wake_lock(const char *buf);
+extern int pm_wake_unlock(const char *buf);
+
+#endif /* !CONFIG_PM_WAKELOCKS */
Index: linux/kernel/power/Kconfig
===================================================================
--- linux.orig/kernel/power/Kconfig
+++ linux/kernel/power/Kconfig
@@ -111,6 +111,14 @@ config PM_AUTOSLEEP
 	Allow the kernel to trigger a system transition into a global sleep
 	state automatically whenever there are no active wakeup sources.
 
+config PM_WAKELOCKS
+	bool "User space wakeup sources interface"
+	depends on PM_SLEEP
+	default n
+	---help---
+	Allow user space to create, activate and deactivate wakeup source
+	objects with the help of a sysfs-based interface.
+
 config PM_RUNTIME
 	bool "Run-time PM core functionality"
 	depends on !IA64_HP_SIM
Index: linux/kernel/power/wakelock.c
===================================================================
--- /dev/null
+++ linux/kernel/power/wakelock.c
@@ -0,0 +1,218 @@
+/*
+ * kernel/power/wakelock.c
+ *
+ * User space wakeup sources support.
+ *
+ * Copyright (C) 2012 Rafael J. Wysocki <rjw@sisk.pl>
+ *
+ * This code is based on the analogous interface allowing user space to
+ * manipulate wakelocks on Android.
+ */
+
+#include <linux/ctype.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/hrtimer.h>
+#include <linux/list.h>
+#include <linux/rbtree.h>
+#include <linux/slab.h>
+
+#define WL_NUMBER_LIMIT	100
+#define WL_GC_COUNT_MAX	100
+#define WL_GC_TIME_SEC	300
+
+static DEFINE_MUTEX(wakelocks_lock);
+
+struct wakelock {
+	char			*name;
+	struct rb_node		node;
+	struct wakeup_source	ws;
+	struct list_head	lru;
+};
+
+static struct rb_root wakelocks_tree = RB_ROOT;
+static LIST_HEAD(wakelocks_lru_list);
+static unsigned int number_of_wakelocks;
+static unsigned int wakelocks_gc_count;
+
+ssize_t pm_show_wakelocks(char *buf, bool show_active)
+{
+	struct rb_node *node;
+	struct wakelock *wl;
+	char *str = buf;
+	char *end = buf + PAGE_SIZE;
+
+	mutex_lock(&wakelocks_lock);
+
+	for (node = rb_first(&wakelocks_tree); node; node = rb_next(node)) {
+		bool active;
+
+		wl = rb_entry(node, struct wakelock, node);
+		spin_lock_irq(&wl->ws.lock);
+		active = wl->ws.active;
+		spin_unlock_irq(&wl->ws.lock);
+		if (active == show_active)
+			str += scnprintf(str, end - str, "%s ", wl->name);
+	}
+	str += scnprintf(str, end - str, "\n");
+
+	mutex_unlock(&wakelocks_lock);
+	return (str - buf);
+}
+
+static struct wakelock *wakelock_lookup_add(const char *name, size_t len,
+					    bool add_if_not_found)
+{
+	struct rb_node **node = &wakelocks_tree.rb_node;
+	struct rb_node *parent = *node;
+	struct wakelock *wl;
+
+	while (*node) {
+		int diff;
+
+		wl = rb_entry(*node, struct wakelock, node);
+		diff = strncmp(name, wl->name, len);
+		if (diff == 0) {
+			if (wl->name[len])
+				diff = -1;
+			else
+				return wl;
+		}
+		if (diff < 0)
+			node = &(*node)->rb_left;
+		else
+			node = &(*node)->rb_right;
+
+		parent = *node;
+	}
+	if (!add_if_not_found)
+		return ERR_PTR(-EINVAL);
+
+	if (number_of_wakelocks > WL_NUMBER_LIMIT)
+		return ERR_PTR(-ENOSPC);
+
+	/* Not found, we have to add a new one. */
+	wl = kzalloc(sizeof(*wl), GFP_KERNEL);
+	if (!wl)
+		return ERR_PTR(-ENOMEM);
+
+	wl->name = kstrndup(name, len, GFP_KERNEL);
+	if (!wl->name) {
+		kfree(wl);
+		return ERR_PTR(-ENOMEM);
+	}
+	wl->ws.name = wl->name;
+	wakeup_source_add(&wl->ws);
+	rb_link_node(&wl->node, parent, node);
+	rb_insert_color(&wl->node, &wakelocks_tree);
+	list_add(&wl->lru, &wakelocks_lru_list);
+	number_of_wakelocks++;
+	return wl;
+}
+
+int pm_wake_lock(const char *buf)
+{
+	const char *str = buf;
+	struct wakelock *wl;
+	u64 timeout_ns = 0;
+	size_t len;
+	int ret = 0;
+
+	while (*str && !isspace(*str))
+		str++;
+
+	len = str - buf;
+	if (!len)
+		return -EINVAL;
+
+	if (*str && *str != '\n') {
+		/* Find out if there's a valid timeout string appended. */
+		ret = kstrtou64(skip_spaces(str), 10, &timeout_ns);
+		if (ret)
+			return -EINVAL;
+	}
+
+	mutex_lock(&wakelocks_lock);
+
+	wl = wakelock_lookup_add(buf, len, true);
+	if (IS_ERR(wl)) {
+		ret = PTR_ERR(wl);
+		goto out;
+	}
+	if (timeout_ns) {
+		u64 timeout_ms = timeout_ns + NSEC_PER_MSEC - 1;
+
+		do_div(timeout_ms, NSEC_PER_MSEC);
+		__pm_wakeup_event(&wl->ws, timeout_ms);
+	} else {
+		__pm_stay_awake(&wl->ws);
+	}
+
+	list_move(&wl->lru, &wakelocks_lru_list);
+
+ out:
+	mutex_unlock(&wakelocks_lock);
+	return ret;
+}
+
+static void wakelocks_gc(void)
+{
+	struct wakelock *wl, *aux;
+	ktime_t now = ktime_get();
+
+	list_for_each_entry_safe_reverse(wl, aux, &wakelocks_lru_list, lru) {
+		u64 idle_time_ns;
+		bool active;
+
+		spin_lock_irq(&wl->ws.lock);
+		idle_time_ns = ktime_to_ns(ktime_sub(now, wl->ws.last_time));
+		active = wl->ws.active;
+		spin_unlock_irq(&wl->ws.lock);
+
+		if (idle_time_ns < ((u64)WL_GC_TIME_SEC * NSEC_PER_SEC))
+			break;
+
+		if (!active) {
+			wakeup_source_remove(&wl->ws);
+			rb_erase(&wl->node, &wakelocks_tree);
+			list_del(&wl->lru);
+			kfree(wl->name);
+			kfree(wl);
+			number_of_wakelocks--;
+		}
+	}
+	wakelocks_gc_count = 0;
+}
+
+int pm_wake_unlock(const char *buf)
+{
+	struct wakelock *wl;
+	size_t len;
+	int ret = 0;
+
+	len = strlen(buf);
+	if (!len)
+		return -EINVAL;
+
+	if (buf[len-1] == '\n')
+		len--;
+
+	if (!len)
+		return -EINVAL;
+
+	mutex_lock(&wakelocks_lock);
+
+	wl = wakelock_lookup_add(buf, len, false);
+	if (IS_ERR(wl)) {
+		ret = PTR_ERR(wl);
+		goto out;
+	}
+	__pm_relax(&wl->ws);
+	list_move(&wl->lru, &wakelocks_lru_list);
+	if (++wakelocks_gc_count > WL_GC_COUNT_MAX)
+		wakelocks_gc();
+
+ out:
+	mutex_unlock(&wakelocks_lock);
+	return ret;
+}
Index: linux/kernel/power/Makefile
===================================================================
--- linux.orig/kernel/power/Makefile
+++ linux/kernel/power/Makefile
@@ -10,5 +10,6 @@ obj-$(CONFIG_PM_TEST_SUSPEND)	+= suspend
 obj-$(CONFIG_HIBERNATION)	+= hibernate.o snapshot.o swap.o user.o \
 				   block_io.o
 obj-$(CONFIG_PM_AUTOSLEEP)	+= autosleep.o
+obj-$(CONFIG_PM_WAKELOCKS)	+= wakelock.o
 
 obj-$(CONFIG_MAGIC_SYSRQ)	+= poweroff.o
Index: linux/drivers/base/power/wakeup.c
===================================================================
--- linux.orig/drivers/base/power/wakeup.c
+++ linux/drivers/base/power/wakeup.c
@@ -132,6 +132,7 @@ void wakeup_source_add(struct wakeup_sou
 	spin_lock_init(&ws->lock);
 	setup_timer(&ws->timer, pm_wakeup_timer_fn, (unsigned long)ws);
 	ws->active = false;
+	ws->last_time = ktime_get();
 
 	spin_lock_irq(&events_lock);
 	list_add_rcu(&ws->entry, &wakeup_sources);
Index: linux/Documentation/ABI/testing/sysfs-power
===================================================================
--- linux.orig/Documentation/ABI/testing/sysfs-power
+++ linux/Documentation/ABI/testing/sysfs-power
@@ -189,3 +189,45 @@ Description:
 
 		Reading from this file causes the last string successfully
 		written to it to be displayed.
+
+What:		/sys/power/wake_lock
+Date:		February 2012
+Contact:	Rafael J. Wysocki <rjw@sisk.pl>
+Description:
+		The /sys/power/wake_lock file allows user space to create
+		wakeup source objects and activate them on demand (if one of
+		those wakeup sources is active, reads from the
+		/sys/power/wakeup_count file block or return false).  When a
+		string without white space is written to /sys/power/wake_lock,
+		it will be assumed to represent a wakeup source name.  If there
+		is a wakeup source object with that name, it will be activated
+		(unless active already).  Otherwise, a new wakeup source object
+		will be registered, assigned the given name and activated.
+		If a string written to /sys/power/wake_lock contains white
+		space, the part of the string preceding the white space will be
+		regarded as a wakeup source name and handled as descrived above.
+		The other part of the string will be regarded as a timeout (in
+		nanoseconds) such that the wakeup source will be automatically
+		deactivated after it has expired.  The timeout, if present, is
+		set regardless of the current state of the wakeup source object
+		in question.
+
+		Reads from this file return a string consisting of the names of
+		wakeup sources created with the help of it that are active at
+		the moment, separated with spaces.
+
+
+What:		/sys/power/wake_unlock
+Date:		February 2012
+Contact:	Rafael J. Wysocki <rjw@sisk.pl>
+Description:
+		The /sys/power/wake_unlock file allows user space to deactivate
+		wakeup sources created with the help of /sys/power/wake_lock.
+		When a string is written to /sys/power/wake_unlock, it will be
+		assumed to represent the name of a wakeup source to deactivate.
+		If a wakeup source object of that name exists and is active at
+		the moment, it will be deactivated.
+
+		Reads from this file return a string consisting of the names of
+		wakeup sources created with the help of /sys/power/wake_lock
+		that are inactive at the moment, separated with spaces.