On Thursday, July 16, 2015 09:33:02 AM Pali Rohár wrote:

On Thursday 16 July 2015 03:02:03 Rafael J. Wysocki wrote:

quoted

On Sunday, June 21, 2015 01:20:32 PM Pali Rohár wrote:

quoted

To prevent race conditions on userspace processes with I/O some taks must be
called after processes are freezed. This patch adds new events which are
delivered by pm_notifier_call_chain() after freezing processes when doing
suspend or hibernate action.

Signed-off-by: Pali Rohár <redacted>
---
 include/linux/suspend.h  |    2 ++
 kernel/power/hibernate.c |    2 ++
 kernel/power/suspend.c   |    4 +++-
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/include/linux/suspend.h b/include/linux/suspend.h
index 5efe743..bc743c8 100644
--- a/include/linux/suspend.h
+++ b/include/linux/suspend.h

@@ -368,6 +368,8 @@ static inline bool hibernation_available(void) { return false; }
 #define PM_POST_SUSPEND		0x0004 /* Suspend finished */
 #define PM_RESTORE_PREPARE	0x0005 /* Going to restore a saved image */
 #define PM_POST_RESTORE		0x0006 /* Restore failed */
+#define PM_HIBERNATION_AFTER_FREEZE	0x0007 /* After hibernation freeze */
+#define PM_SUSPEND_AFTER_FREEZE		0x0008 /* After suspend freeze */
 
 extern struct mutex pm_mutex;
 

diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 2329daa..184f7ee 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c

@@ -671,6 +671,8 @@ int hibernate(void)
 	if (error)
 		goto Exit;
 
+	pm_notifier_call_chain(PM_HIBERNATION_AFTER_FREEZE);

Don't we need to check errors from these?

If yes, what to do in this case? Fail hibernation and goto Exit?

Yes, fail the transition in progress.

quoted

Also, if you're adding AFTER_FREEZE, it would be good to add BEFORE_THAW too
for symmetry.

But there is no use case for BEFORE_THAW. At least it is not needed for now.

For your use case, a single function pointer would be sufficient too.

quoted

quoted

+
 	lock_device_hotplug();
 	/* Allocate memory management structures */
 	error = create_basic_memory_bitmaps();

diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 8d7a1ef..ba2a945 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c

@@ -277,8 +277,10 @@ static int suspend_prepare(suspend_state_t state)
 	trace_suspend_resume(TPS("freeze_processes"), 0, true);
 	error = suspend_freeze_processes();
 	trace_suspend_resume(TPS("freeze_processes"), 0, false);
-	if (!error)
+	if (!error) {
+		pm_notifier_call_chain(PM_SUSPEND_AFTER_FREEZE);
 		return 0;
+	}
 
 	suspend_stats.failed_freeze++;
 	dpm_save_failed_step(SUSPEND_FREEZE);

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.