Messages in this thread | | | Date | Mon, 31 Jul 2006 13:49:31 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] bug in futex unqueue_me |
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* Christian Borntraeger <borntrae@de.ibm.com> wrote:
> On Sunday 30 July 2006 08:38, Ingo Molnar wrote: > > interesting, how is this possible? We do a spin_lock(lock_ptr), and > > taking a spinlock is an implicit barrier(). So gcc must not delay > > evaluating lock_ptr to inside the critical section. And as far as i can > > see the s390 spinlock implementation goes through an 'asm volatile' > > piece of code, which is a barrier already. So how could this have > > happened? > > spin_lock is a barrier, but isnt the barrierness too late here? The > compiler reloads the value of lock_ptr after the "if(lock_ptr)" and > *before* calling spin_lock(lock_ptr):
ah, indeed. So your patch is a real fix. Thanks,
Acked-by: Ingo Molnar <mingo@elte.hu>
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