On 08/05/15 10:36, Jan Beulich wrote:
>>
>> + }
>> + }
>> smp_mb();
>> }
>
> The old code had smp_mb() before _and_ after the check - is it really
> correct to drop the one before (or effectively replace it by smp_rmb()
> in observe_{lock,head}())?
Typical usage is:
d->is_dying = DOMDYING_dying;
spin_barrier(&d->domain_lock);
So there needs to be a barrier before we check that the lock is
released. i.e., I removed the wrong smp_mb().
I don't see the need for the second barrier since there's no stores in
_spin_barrier() and observe_lock() and observe_head() both have their
required read barriers.
David
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