linux-kernel - [PATCH 3/3] PM / Sleep: Make __pm_stay_awake() delete wakeup source timers

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Date:	Wed, 15 Feb 2012 23:24:07 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Linux PM list <linux-pm@...r.kernel.org>
Cc:	Arve Hjønnevåg <arve@...roid.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 3/3] PM / Sleep: Make __pm_stay_awake() delete wakeup source timers

From: Rafael J. Wysocki <rjw@...k.pl>

If __pm_stay_awake() is called after __pm_wakeup_event() for the same
wakep source object before its timer expires, it won't cancel the
timer, so the wakeup source will be deactivated from the timer
function as scheduled by __pm_wakeup_event().  In that case
__pm_stay_awake() doesn't have any effect beyond incrementing
the wakeup source's event_count field, although it should cancel
the timer and make the wakeup source stay active until __pm_relax()
is called for it.

Conversely, if __pm_wakeup_event() is called for a wakeup source
that has been activated by __pm_stay_awake() before, it will set up
the timer to deactivate the wakeup source, although it should leave
it active until __pm_relax() is called for it.

To fix the first of these problems make __pm_stay_awake() delete the
wakeup source's timer and ensure that it won't be deactivated from
the timer funtion afterwards by clearing its timer_expires field.

To fix the second one, make __pm_wakeup_event() skip setting up the
timer if it sees that the wakeup source is active and its
timer_expires field is zero, which means that it has been activated
by __pm_stay_awake().

Reported-by: Arve Hjønnevåg <arve@...roid.com>
Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
---
 drivers/base/power/wakeup.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Index: linux/drivers/base/power/wakeup.c
===================================================================
--- linux.orig/drivers/base/power/wakeup.c
+++ linux/drivers/base/power/wakeup.c
@@ -365,9 +365,15 @@ void __pm_stay_awake(struct wakeup_sourc
 		return;

 	spin_lock_irqsave(&ws->lock, flags);
+
+	del_timer(&ws->timer);
+	ws->timer_expires = 0;
+
 	ws->event_count++;
+
 	if (!ws->active)
 		wakeup_source_activate(ws);
+
 	spin_unlock_irqrestore(&ws->lock, flags);
 }
 EXPORT_SYMBOL_GPL(__pm_stay_awake);
@@ -529,8 +535,12 @@ void __pm_wakeup_event(struct wakeup_sou
 	spin_lock_irqsave(&ws->lock, flags);

 	ws->event_count++;
-	if (!ws->active)
+	if (ws->active) {
+		if (!ws->timer_expires)
+			goto unlock;
+	} else {
 		wakeup_source_activate(ws);
+	}

 	if (!msec) {
 		wakeup_source_deactivate(ws);

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