wakeup: Use irqsave/irqrestore for events_lock
John Stultz [Thu, 6 Sep 2012 18:07:37 +0000 (14:07 -0400)]
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@sisk.pl>
Cc: Android Team <kernel-team@android.com>
Cc: Arve Hjønnevåg <arve@android.com>
Cc: Jon Medhurst (Tixy) <tixy@linaro.org>
Reported-and-debugged-by: Jon Medhurst (Tixy) <tixy@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Change-Id: Id455188931229f04e353969af389e49b069cb34c

drivers/base/power/wakeup.c

index f39cb39..c9a15bc 100644 (file)
@@ -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);
@@ -760,15 +764,16 @@ 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;
 }