Re: [RFC][PATCH -mm 1/3] PM: Hibernation and suspend notifiers

Rafael J. Wysocki
2007-05-29T22:24:31Z

On Monday, 28 May 2007 17:56, Alan Stern wrote:
> On Sun, 27 May 2007, Rafael J. Wysocki wrote:
>
> > From: Rafael J. Wysocki <rjw@sisk.pl>
> >
> > Make it possible to register hibernation and suspend notifiers, so that
> > subsystems can perform hibernation-related or suspend-related operations that
> > should not be carried out by device drivers' .suspend() and .resume() routines.
>
> > +static DEFINE_MUTEX(pm_notifier_lock);
> > +
> > +static RAW_NOTIFIER_HEAD(pm_chain);
>
> Is there any particular reason you chose to use a RAW_NOTIFIER_HEAD
> with an explicit mutex instead of using a BLOCKING_NOTIFIER_HEAD?

Yes, this makes the patch simpler.

I have also followed the Pavel's suggestion to limit the nubmer of events.

Please have a look at the updated version of the patch (appended).

Greetings,
Rafael

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

Make it possible to register hibernation and suspend notifiers, so that
subsystems can perform hibernation-related or suspend-related operations that
should not be carried out by device drivers' .suspend() and .resume() routines.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

Documentation/power/notifiers.txt | 57 ++++++++++++++++++++++++++++++++++++++
include/linux/notifier.h | 8 +++++
include/linux/suspend.h | 37 ++++++++++++++++++++++--
kernel/power/disk.c | 24 ++++++++++++----
kernel/power/main.c | 14 +++++++++
kernel/power/power.h | 10 ++++++
kernel/power/user.c | 11 +++++--
7 files changed, 150 insertions(+), 11 deletions(-)

Index: linux-2.6.22-rc3/include/linux/suspend.h
===================================================================
--- linux-2.6.22-rc3.orig/include/linux/suspend.h 2007-05-27 19:57:21.000000000 +0200
+++ linux-2.6.22-rc3/include/linux/suspend.h 2007-05-29 22:52:24.000000000 +0200
@@ -54,7 +54,8 @@ struct hibernation_ops {
void (*restore_cleanup)(void);
};

-#if defined(CONFIG_PM) && defined(CONFIG_SOFTWARE_SUSPEND)
+#ifdef CONFIG_PM
+#ifdef CONFIG_SOFTWARE_SUSPEND
/* kernel/power/snapshot.c */
extern void __register_nosave_region(unsigned long b, unsigned long e, int km);
static inline void register_nosave_region(unsigned long b, unsigned long e)
@@ -72,7 +73,7 @@ extern unsigned long get_safe_page(gfp_t

extern void hibernation_set_ops(struct hibernation_ops *ops);
extern int hibernate(void);
-#else
+#else /* CONFIG_SOFTWARE_SUSPEND */
static inline void register_nosave_region(unsigned long b, unsigned long e) {}
static inline void register_nosave_region_late(unsigned long b, unsigned long e) {}
static inline int swsusp_page_is_forbidden(struct page *p) { return 0; }
@@ -81,7 +82,7 @@ static inline void swsusp_unset_page_fre

static inline void hibernation_set_ops(struct hibernation_ops *ops) {}
static inline int hibernate(void) { return -ENOSYS; }
-#endif /* defined(CONFIG_PM) && defined(CONFIG_SOFTWARE_SUSPEND) */
+#endif /* CONFIG_SOFTWARE_SUSPEND */

void save_processor_state(void);
void restore_processor_state(void);
@@ -89,4 +90,34 @@ struct saved_context;
void __save_processor_state(struct saved_context *ctxt);
void __restore_processor_state(struct saved_context *ctxt);

+/* kernel/power/main.c */
+extern struct blocking_notifier_head pm_chain_head;
+
+static inline int register_pm_notifier(struct notifier_block *nb)
+{
+ return blocking_notifier_chain_register(&pm_chain_head, nb);
+}
+
+static inline int unregister_pm_notifier(struct notifier_block *nb)
+{
+ return blocking_notifier_chain_unregister(&pm_chain_head, nb);
+}
+
+#define pm_notifier(fn, pri) { \
+ static struct notifier_block fn##_nb = \
+ { .notifier_call = fn, .priority = pri }; \
+ register_pm_notifier(&fn##_nb); \
+}
+#else /* CONFIG_PM */
+static inline int register_pm_notifier(struct notifier_block *nb) {
+ return 0;
+}
+
+static inline int unregister_pm_notifier(struct notifier_block *nb) {
+ return 0;
+}
+
+#define pm_notifier(fn, pri) do { (void)(fn); } while (0)
+#endif /* CONFIG_PM */
+
#endif /* _LINUX_SWSUSP_H */
Index: linux-2.6.22-rc3/kernel/power/power.h
===================================================================
--- linux-2.6.22-rc3.orig/kernel/power/power.h 2007-05-27 19:57:21.000000000 +0200
+++ linux-2.6.22-rc3/kernel/power/power.h 2007-05-29 22:53:12.000000000 +0200
@@ -173,5 +173,15 @@ extern void swsusp_close(void);
extern int suspend_enter(suspend_state_t state);

struct timeval;
+/* kernel/power/swsusp.c */
extern void swsusp_show_speed(struct timeval *, struct timeval *,
unsigned int, char *);
+
+/* kernel/power/main.c */
+extern struct blocking_notifier_head pm_chain_head;
+
+static inline int pm_notifier_call_chain(unsigned long val)
+{
+ return (blocking_notifier_call_chain(&pm_chain_head, val, NULL)
+ == NOTIFY_BAD) ? -EINVAL : 0;
+}
Index: linux-2.6.22-rc3/include/linux/notifier.h
===================================================================
--- linux-2.6.22-rc3.orig/include/linux/notifier.h 2007-05-27 19:57:21.000000000 +0200
+++ linux-2.6.22-rc3/include/linux/notifier.h 2007-05-29 22:58:13.000000000 +0200
@@ -209,5 +209,13 @@ extern int __srcu_notifier_call_chain(st
#define CPU_DOWN_FAILED_FROZEN (CPU_DOWN_FAILED | CPU_TASKS_FROZEN)
#define CPU_DEAD_FROZEN (CPU_DEAD | CPU_TASKS_FROZEN)

+/* Hibernation and suspend events */
+#define PM_PRE_FREEZE 0x0001 /* Going to freeze tasks */
+#define PM_POST_THAW 0x0002 /* Tasks have just been thawed */
+#define PM_HIBERNATION_PREPARE 0x0003 /* Tasks frozen, going to hibernate */
+#define PM_POST_HIBERNATION 0x0004 /* Hibernation finished, thawing tasks */
+#define PM_SUSPEND_PREPARE 0x0005 /* Going to suspend the system */
+#define PM_POST_SUSPEND 0x0006 /* Suspend finished */
+
#endif /* __KERNEL__ */
#endif /* _LINUX_NOTIFIER_H */
Index: linux-2.6.22-rc3/kernel/power/disk.c
===================================================================
--- linux-2.6.22-rc3.orig/kernel/power/disk.c 2007-05-27 19:57:21.000000000 +0200
+++ linux-2.6.22-rc3/kernel/power/disk.c 2007-05-30 00:26:41.000000000 +0200
@@ -130,10 +130,14 @@ int hibernation_snapshot(int platform_mo
{
int error;

+ error = pm_notifier_call_chain(PM_HIBERNATION_PREPARE);
+ if (error)
+ return error;
+
/* Free memory before shutting down devices. */
error = swsusp_shrink_memory();
if (error)
- return error;
+ goto Finish;

suspend_console();
error = device_suspend(PMSG_FREEZE);
@@ -161,6 +165,8 @@ int hibernation_snapshot(int platform_mo
device_resume();
Resume_console:
resume_console();
+ Finish:
+ pm_notifier_call_chain(PM_POST_HIBERNATION);
return error;
}

@@ -259,12 +265,17 @@ static void unprepare_processes(void)
{
thaw_processes();
pm_restore_console();
+ pm_notifier_call_chain(PM_POST_THAW);
}

static int prepare_processes(void)
{
int error = 0;

+ error = pm_notifier_call_chain(PM_PRE_FREEZE);
+ if (error)
+ return error;
+
pm_prepare_console();
if (freeze_processes()) {
error = -EBUSY;
@@ -281,9 +292,12 @@ int hibernate(void)
{
int error;

+ mutex_lock(&pm_mutex);
/* The snapshot device should not be opened while we're running */
- if (!atomic_add_unless(&snapshot_device_available, -1, 0))
- return -EBUSY;
+ if (!atomic_add_unless(&snapshot_device_available, -1, 0)) {
+ error = -EBUSY;
+ goto Unlock;
+ }

/* Allocate memory management structures */
error = create_basic_memory_bitmaps();
@@ -294,7 +308,6 @@ int hibernate(void)
if (error)
goto Finish;

- mutex_lock(&pm_mutex);
if (hibernation_mode == HIBERNATION_TESTPROC) {
printk("swsusp debug: Waiting for 5 seconds.\n");
mdelay(5000);
@@ -316,12 +329,13 @@ int hibernate(void)
swsusp_free();
}
Thaw:
- mutex_unlock(&pm_mutex);
unprepare_processes();
Finish:
free_basic_memory_bitmaps();
Exit:
atomic_inc(&snapshot_device_available);
+ Unlock:
+ mutex_unlock(&pm_mutex);
return error;
}

Index: linux-2.6.22-rc3/kernel/power/main.c
===================================================================
--- linux-2.6.22-rc3.orig/kernel/power/main.c 2007-05-27 19:57:21.000000000 +0200
+++ linux-2.6.22-rc3/kernel/power/main.c 2007-05-29 22:54:30.000000000 +0200
@@ -24,6 +24,8 @@

#include "power.h"

+BLOCKING_NOTIFIER_HEAD(pm_chain_head);
+
/*This is just an arbitrary number */
#define FREE_PAGE_NUMBER (100)

@@ -82,6 +84,10 @@ static int suspend_prepare(suspend_state
if (!pm_ops || !pm_ops->enter)
return -EPERM;

+ error = pm_notifier_call_chain(PM_PRE_FREEZE);
+ if (error)
+ return error;
+
pm_prepare_console();

if (freeze_processes()) {
@@ -89,6 +95,10 @@ static int suspend_prepare(suspend_state
goto Thaw;
}

+ error = pm_notifier_call_chain(PM_SUSPEND_PREPARE);
+ if (error)
+ return error;
+
if ((free_pages = global_page_state(NR_FREE_PAGES))
< FREE_PAGE_NUMBER) {
pr_debug("PM: free some memory\n");
@@ -121,9 +131,11 @@ static int suspend_prepare(suspend_state
device_resume();
Resume_console:
resume_console();
+ pm_notifier_call_chain(PM_POST_SUSPEND);
Thaw:
thaw_processes();
pm_restore_console();
+ pm_notifier_call_chain(PM_POST_THAW);
return error;
}

@@ -173,8 +185,10 @@ static void suspend_finish(suspend_state
pm_finish(state);
device_resume();
resume_console();
+ pm_notifier_call_chain(PM_POST_SUSPEND);
thaw_processes();
pm_restore_console();
+ pm_notifier_call_chain(PM_POST_THAW);
}

Index: linux-2.6.22-rc3/kernel/power/user.c
===================================================================
--- linux-2.6.22-rc3.orig/kernel/power/user.c 2007-05-27 19:57:21.000000000 +0200
+++ linux-2.6.22-rc3/kernel/power/user.c 2007-05-29 22:35:08.000000000 +0200
@@ -149,9 +149,13 @@ static int snapshot_ioctl(struct inode *
if (data->frozen)
break;
mutex_lock(&pm_mutex);
- if (freeze_processes()) {
- thaw_processes();
- error = -EBUSY;
+ error = pm_notifier_call_chain(PM_PRE_FREEZE);
+ if (!error) {
+ error = freeze_processes();
+ if (error) {
+ thaw_processes();
+ pm_notifier_call_chain(PM_POST_THAW);
+ }
}
mutex_unlock(&pm_mutex);
if (!error)
@@ -163,6 +167,7 @@ static int snapshot_ioctl(struct inode *
break;
mutex_lock(&pm_mutex);
thaw_processes();
+ pm_notifier_call_chain(PM_POST_THAW);
mutex_unlock(&pm_mutex);
data->frozen = 0;
break;
Index: linux-2.6.22-rc3/Documentation/power/notifiers.txt
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.22-rc3/Documentation/power/notifiers.txt 2007-05-29 23:04:20.000000000 +0200
@@ -0,0 +1,57 @@
+Suspend notifiers
+ (C) 2007 Rafael J. Wysocki <rjw@sisk.pl>, GPL
+
+There are some operations that device drivers may want to carry out in their
+.suspend() routines, but shouldn't, because they can cause the hibernation or
+suspend to fail. For example, a driver may want to allocate a substantial amount
+of memory (like 50 MB) in .suspend(), but that shouldn't be done after the
+swsusp's memory shrinker has run.
+
+Also, there may be some operations, that subsystems want to carry out before a
+hibernation/suspend or after a restore/resume, requiring the system to be fully
+functional, so the drivers' .suspend() and .resume() routines are not suitable
+for this purpose. For example, device drivers may want to upload firmware to
+their devices after a restore from a hibernation image, but they cannot do it by
+calling request_firmware() from their .resume() routines (user land processes
+are frozen at this point). The solution may be to load the firmware into
+memory before processes are frozen and upload it from there in the .resume()
+routine. Of course, a hibernation notifier may be used for this purpose.
+
+The subsystems that have such needs can register suspend notifiers that will be
+called upon the following events by the suspend core:
+
+PM_PRE_FREEZE The system is going to hibernate or suspend, tasks will
+ be frozen immediately
+
+PM_POST_THAW Tasks have just been thawed after a resume or restore
+ from a hibernation image
+
+PM_HIBERNATION_PREPARE The system is preparing for hibernation. Tasks have
+ been frozen, memory is going to be freed and devices
+ are going to be suspended.
+
+PM_POST_HIBERNATION The system memory state has been restored from a
+ hibernation image or an error occured during the
+ hibernation. Device drivers' .resume() callbacks have
+ been executed, tasks will be thawed immediately.
+
+PM_SUSPEND_PREPARE The system is preparing for a suspend. Tasks have been
+ frozen, devices are going to be suspended.
+
+PM_POST_SUSPEND The system has just resumed or an error occured during
+ the suspend. Device drivers' .resume() callbacks have
+ been executed, tasks will be thawed immediately.
+
+It is generally assumed that whatever the notifiers do for PM_PRE_FREEZE,
+should be undone for PM_POST_THAW. Moreover, what is done for
+PM_HIBERNATION_PREPARE, should be undone for PM_POST_HIBERNATION (eg. if memory
+is allocated for PM_HIBERNATION_PREPARE, it should be freed for
+PM_POST_HIBERNATION). Analogously, operations performed for PM_SUSPEND_PREPARE
+should be reversed for PM_POST_SUSPEND.
+
+The hibernation and suspend notifiers are called with pm_mutex held. They are
+defined in the usual way, but their last argument is meaningless (it is always
+NULL). To register and/or unregister a suspend notifier use the functions
+register_pm_notifier() and unregister_pm_notifier(), respectively, defined in
+include/linux/suspend.h . If you don't need to unregister the notifier, you can
+also use the pm_notifier() macro defined in include/linux/suspend.h .