On 05/13, Paul E. McKenney wrote: > > On Tue, May 13, 2014 at 05:44:35PM +0200, Peter Zijlstra wrote: > > > > Ah, yes, so I'll defer to Oleg and Linus to explain that one. As per the > > name: smp_mb__before_spinlock() should of course imply a full barrier. > > How about if I queue a name change to smp_wmb__before_spinlock()? I agree, this is more accurate, simply because it describes what it actually does. But just in case, as for try_to_wake_up() it does not actually need wmb() between "CONDITION = T" and "task->state = RUNNING". It would be fine if these 2 STORE's are re-ordered, we can rely on rq->lock. What it actually needs is a barrier between "CONDITION = T" and "task->state & state" check. But since we do not have a store-load barrier, wmb() was added to ensure that "CONDITION = T" can't leak into the critical section. But it seems that set_tlb_flush_pending() already assumes that it acts as wmb(), so probably smp_wmb__before_spinlock() is fine. Oleg. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>