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SubjectRe: Question on mutex code
On 03/16/15 00:10, Rabin Vincent wrote:
> On Sun, Mar 15, 2015 at 11:49:07PM +0200, Matthias Bonne wrote:
>> So the counter is set to 1 before taking the spinlock, which I think
>> might cause the race. Did I miss something?
>
> Yes, you miss the fact that __mutex_slowpath_needs_to_unlock() is 0 for
> the CONFIG_DEBUG_MUTEXES case:
>
> #ifdef CONFIG_DEBUG_MUTEXES
> # include "mutex-debug.h"
> # include <asm-generic/mutex-null.h>
> /*
> * Must be 0 for the debug case so we do not do the unlock outside of the
> * wait_lock region. debug_mutex_unlock() will do the actual unlock in this
> * case.
> */
> # undef __mutex_slowpath_needs_to_unlock
> # define __mutex_slowpath_needs_to_unlock() 0
>

Right, I overlooked this part. Thanks to both of you for the
clarifications.


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