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sched: Make wakeup side and atomic variants of completion API irq safe

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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>
This commit is contained in:
Rafael J. Wysocki 2009-12-13 00:07:30 +01:00 committed by Ingo Molnar
parent f40542532e
commit 7539a3b3d1
1 changed files with 6 additions and 4 deletions
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10
kernel/sched.c
View 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);