[PATCH 4.14 057/178] PM / s2idle: Clear the events_check_enabled flag

From: Greg Kroah-Hartman
Date: Mon Dec 18 2017 - 11:47:12 EST

4.14-stable review patch. If anyone has any objections, please let me know.


From: Rajat Jain <rajatja@xxxxxxxxxx>

[ 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.

Signed-off-by: Rajat Jain <rajatja@xxxxxxxxxx>
Acked-by: Pavel Machek <pavel@xxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
kernel/power/suspend.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -437,7 +437,6 @@ static int suspend_enter(suspend_state_t
error = suspend_ops->enter(state);
state, false);
- events_check_enabled = false;
} else if (*wakeup) {
error = -EBUSY;
@@ -582,6 +581,7 @@ static int enter_state(suspend_state_t s

+ events_check_enabled = false;
pm_pr_dbg("Finishing wakeup.\n");