linux-kernel - [PATCH 4.14 057/178] PM / s2idle: Clear the events_check

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Date:   Mon, 18 Dec 2017 16:48:13 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Rajat Jain <rajatja@...gle.com>,
        Pavel Machek <pavel@....cz>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.14 057/178] PM / s2idle: Clear the events_check_enabled flag

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

------------------

From: Rajat Jain <rajatja@...gle.com>

[ 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@...gle.com>
Acked-by: Pavel Machek <pavel@....cz>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 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);
 			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: