linux-kernel - [PATCH] wakeup: Use irqsave/irqrestore for events

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Date:	Thu,  6 Sep 2012 14:07:37 -0400
From:	John Stultz <john.stultz@...aro.org>
To:	lkml <linux-kernel@...r.kernel.org>
Cc:	John Stultz <john.stultz@...aro.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Android Team <kernel-team@...roid.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	"Jon Medhurst (Tixy)" <tixy@...aro.org>
Subject: [PATCH] wakeup: Use irqsave/irqrestore for events_lock

Jon Medhurst (Tixy) recently noticed a problem with the
events_lock usage. One of the Android patches that uses
wakeup_sources calls wakeup_source_add() with irqs disabled.
However, the event_lock usage in wakeup_source_add() uses
spin_lock_irq()/spin_unlock_irq(), which reenables interrupts.
This results in lockdep warnings.

The fix is to use spin_lock_irqsave()/spin_lock_irqrestore()
instead for the events_lock.

Full bug report here:
https://bugs.launchpad.net/linaro-landing-team-arm/+bug/1037565

Cc: Rafael J. Wysocki <rjw@...k.pl>
Cc: Android Team <kernel-team@...roid.com>
Cc: Arve Hjønnevåg <arve@...roid.com>
Cc: Jon Medhurst (Tixy) <tixy@...aro.org>
Reported-and-debugged-by: Jon Medhurst (Tixy) <tixy@...aro.org>
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 drivers/base/power/wakeup.c |   17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
index cbb463b..0e4b093 100644
--- a/drivers/base/power/wakeup.c
+++ b/drivers/base/power/wakeup.c
@@ -127,6 +127,8 @@ EXPORT_SYMBOL_GPL(wakeup_source_destroy);
  */
 void wakeup_source_add(struct wakeup_source *ws)
 {
+	unsigned long flags;
+
 	if (WARN_ON(!ws))
 		return;
 
@@ -135,9 +137,9 @@ void wakeup_source_add(struct wakeup_source *ws)
 	ws->active = false;
 	ws->last_time = ktime_get();
 
-	spin_lock_irq(&events_lock);
+	spin_lock_irqsave(&events_lock, flags);
 	list_add_rcu(&ws->entry, &wakeup_sources);
-	spin_unlock_irq(&events_lock);
+	spin_unlock_irqrestore(&events_lock, flags);
 }
 EXPORT_SYMBOL_GPL(wakeup_source_add);
 
@@ -147,12 +149,14 @@ EXPORT_SYMBOL_GPL(wakeup_source_add);
  */
 void wakeup_source_remove(struct wakeup_source *ws)
 {
+	unsigned long flags;
+
 	if (WARN_ON(!ws))
 		return;
 
-	spin_lock_irq(&events_lock);
+	spin_lock_irqsave(&events_lock, flags);
 	list_del_rcu(&ws->entry);
-	spin_unlock_irq(&events_lock);
+	spin_unlock_irqrestore(&events_lock, flags);
 	synchronize_rcu();
 }
 EXPORT_SYMBOL_GPL(wakeup_source_remove);
@@ -723,15 +727,16 @@ bool pm_get_wakeup_count(unsigned int *count, bool block)
 bool pm_save_wakeup_count(unsigned int count)
 {
 	unsigned int cnt, inpr;
+	unsigned long flags;
 
 	events_check_enabled = false;
-	spin_lock_irq(&events_lock);
+	spin_lock_irqsave(&events_lock, flags);
 	split_counters(&cnt, &inpr);
 	if (cnt == count && inpr == 0) {
 		saved_count = count;
 		events_check_enabled = true;
 	}
-	spin_unlock_irq(&events_lock);
+	spin_unlock_irqrestore(&events_lock, flags);
 	return events_check_enabled;
 }
 
-- 
1.7.9.5

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