Commit 95b982b4 authored Oct 31, 2017 by Rajat Jain Committed by Rafael J. Wysocki Nov 08, 2017

PM / s2idle: Clear the events_check_enabled flag



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.

Signed-off-by: Rajat Jain <rajatja@google.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent 0e708fc6

kernel/power/suspend.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -437,7 +437,6 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
		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 state)
		pm_restore_gfp_mask();

		Finish:
		events_check_enabled = false;
		pm_pr_dbg("Finishing wakeup.\n");
		suspend_finish();
		Unlock: