Patch "PM / s2idle: Clear the events_check_enabled flag" has been added to the 4.14-stable tree

This is a note to let you know that I've just added the patch titled

PM / s2idle: Clear the events_check_enabled flag

to the 4.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
pm-s2idle-clear-the-events_check_enabled-flag.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Rajat Jain <[email protected]>
Date: Tue, 31 Oct 2017 14:44:24 -0700
Subject: PM / s2idle: Clear the events_check_enabled flag

From: Rajat Jain <[email protected]>

[ Upstream commit 95b982b45122c57da2ee0b46cce70775e1d987af ]

Problem: This flag does not get cleared currently in the suspend or resume path in the following cases:

* In case some driver's suspend routine returns an error.
* Successful s2idle case
* etc?

Why is this a problem: What happens is that the next suspend attempt could fail even though the user did not enable the flag by writing to /sys/power/wakeup_count. This is 1 use case how the issue can be seen (but similar use case with driver suspend failure can be thought of):

1. Read /sys/power/wakeup_count
2. echo count > /sys/power/wakeup_count
3. echo freeze > /sys/power/wakeup_count
4. Let the system suspend, and wakeup the system using some wake source that calls pm_wakeup_event() e.g. power button or something.
5. Note that the combined wakeup count would be incremented due to the pm_wakeup_event() in the resume path.
6. After resuming the events_check_enabled flag is still set.

At this point if the user attempts to freeze again (without writing to /sys/power/wakeup_count), the suspend would fail even though there has been no wake event since the past resume.

Address that by clearing the flag just before a resume is completed, so that it is always cleared for the corner cases mentioned above.

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

@@ -437,7 +437,6 @@ static int suspend_enter(suspend_state_t
 			error = suspend_ops->enter(state);
 			trace_suspend_resume(TPS("machine_suspend"),
 				state, false);
-			events_check_enabled = false;
 		} else if (*wakeup) {
 			error = -EBUSY;
 		}

@@ -582,6 +581,7 @@ static int enter_state(suspend_state_t s
 	pm_restore_gfp_mask();
 
  Finish:
+	events_check_enabled = false;
 	pm_pr_dbg("Finishing wakeup.\n");
 	suspend_finish();
  Unlock:

Patches currently in stable-queue which might be from [email protected] are

queue-4.14/pm-s2idle-clear-the-events_check_enabled-flag.patch