Re: [PATCH 10/11] qspinlock: Paravirt support

[Paolo Bonzini]

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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/