linux-kernel - [PATCH 4.4 224/230] PM / wakeup: Rework wakeup source timer cancellation

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Date:   Fri, 22 Mar 2019 12:16:02 +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, Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: [PATCH 4.4 224/230] PM / wakeup: Rework wakeup source timer cancellation

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

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

From: Viresh Kumar <viresh.kumar@...aro.org>

commit 1fad17fb1bbcd73159c2b992668a6957ecc5af8a upstream.

If wakeup_source_add() is called right after wakeup_source_remove()
for the same wakeup source, timer_setup() may be called for a
potentially scheduled timer which is incorrect.

To avoid that, move the wakeup source timer cancellation from
wakeup_source_drop() to wakeup_source_remove().

Moreover, make wakeup_source_remove() clear the timer function after
canceling the timer to let wakeup_source_not_registered() treat
unregistered wakeup sources in the same way as the ones that have
never been registered.

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
Cc: 4.4+ <stable@...r.kernel.org> # 4.4+
[ rjw: Subject, changelog, merged two patches together ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/base/power/wakeup.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/base/power/wakeup.c
+++ b/drivers/base/power/wakeup.c
@@ -113,7 +113,6 @@ void wakeup_source_drop(struct wakeup_so
 	if (!ws)
 		return;

-	del_timer_sync(&ws->timer);
 	__pm_relax(ws);
 }
 EXPORT_SYMBOL_GPL(wakeup_source_drop);
@@ -201,6 +200,13 @@ void wakeup_source_remove(struct wakeup_
 	list_del_rcu(&ws->entry);
 	spin_unlock_irqrestore(&events_lock, flags);
 	synchronize_srcu(&wakeup_srcu);
+
+	del_timer_sync(&ws->timer);
+	/*
+	 * Clear timer.function to make wakeup_source_not_registered() treat
+	 * this wakeup source as not registered.
+	 */
+	ws->timer.function = NULL;
 }
 EXPORT_SYMBOL_GPL(wakeup_source_remove);