sched: Make wakeup side and atomic variants of completion API irq safe
authorRafael J. Wysocki <rjw@sisk.pl>
Sat, 12 Dec 2009 23:07:30 +0000 (00:07 +0100)
committerIngo Molnar <mingo@elte.hu>
Sun, 13 Dec 2009 07:12:46 +0000 (08:12 +0100)
Alan Stern noticed that all the wakeup side (and atomic) variants of the
completion APIs should be irq safe, but the newly introduced
completion_done() and try_wait_for_completion() aren't. The use of the
irq unsafe variants in IRQ contexts can cause crashes/hangs.

Fix the problem by making them use spin_lock_irqsave() and
spin_lock_irqrestore().

Reported-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: pm list <linux-pm@lists.linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: David Chinner <david@fromorbit.com>
Cc: Lachlan McIlroy <lachlan@sgi.com>
LKML-Reference: <200912130007.30541.rjw@sisk.pl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
kernel/sched.c

index ff39cadf621e91834dcdc9116d123f8912eab225..8b3532f262d70bc7a5a306f41efa3e3ba95f253e 100644 (file)
@@ -5908,14 +5908,15 @@ EXPORT_SYMBOL(wait_for_completion_killable);
  */
 bool try_wait_for_completion(struct completion *x)
 {
+       unsigned long flags;
        int ret = 1;
 
-       spin_lock_irq(&x->wait.lock);
+       spin_lock_irqsave(&x->wait.lock, flags);
        if (!x->done)
                ret = 0;
        else
                x->done--;
-       spin_unlock_irq(&x->wait.lock);
+       spin_unlock_irqrestore(&x->wait.lock, flags);
        return ret;
 }
 EXPORT_SYMBOL(try_wait_for_completion);
@@ -5930,12 +5931,13 @@ EXPORT_SYMBOL(try_wait_for_completion);
  */
 bool completion_done(struct completion *x)
 {
+       unsigned long flags;
        int ret = 1;
 
-       spin_lock_irq(&x->wait.lock);
+       spin_lock_irqsave(&x->wait.lock, flags);
        if (!x->done)
                ret = 0;
-       spin_unlock_irq(&x->wait.lock);
+       spin_unlock_irqrestore(&x->wait.lock, flags);
        return ret;
 }
 EXPORT_SYMBOL(completion_done);