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SubjectRe: [PATCH 10/11] qspinlock: Paravirt support
Il 17/06/2014 00:08, Waiman Long ha scritto:
>> +void __pv_queue_unlock(struct qspinlock *lock)
>> +{
>> + int val = atomic_read(&lock->val);
>> +
>> + native_queue_unlock(lock);
>> +
>> + if (val & _Q_LOCKED_SLOW)
>> + ___pv_kick_head(lock);
>> +}
>> +
>
> Again a race can happen here between the reading and writing of the lock
> value. I can't think of a good way to do that without using cmpxchg.

Could you just use xchg on the locked byte?

Paolo


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