On 12/10, Paul E. McKenney wrote: > > On Tue, Dec 10, 2013 at 06:04:04PM +0100, Oleg Nesterov wrote: > > > > I am wondering, perhaps smp_mb__after_unlock() makes more sense? > > > > Note that it already has the potential user: > > > > --- x/kernel/sched/wait.c > > +++ x/kernel/sched/wait.c > > @@ -176,8 +176,9 @@ prepare_to_wait(wait_queue_head_t *q, wa > > spin_lock_irqsave(&q->lock, flags); > > if (list_empty(&wait->task_list)) > > __add_wait_queue(q, wait); > > - set_current_state(state); > > + __set_current_state(state); > > spin_unlock_irqrestore(&q->lock, flags); > > + smp_mb__after_unlock(); > > } > > EXPORT_SYMBOL(prepare_to_wait); > > > > @@ -190,8 +191,9 @@ prepare_to_wait_exclusive(wait_queue_hea > > spin_lock_irqsave(&q->lock, flags); > > if (list_empty(&wait->task_list)) > > __add_wait_queue_tail(q, wait); > > - set_current_state(state); > > + __set_current_state(state); > > spin_unlock_irqrestore(&q->lock, flags); > > + smp_mb__after_unlock(); > > } > > EXPORT_SYMBOL(prepare_to_wait_exclusive); > > > > > > Assuming it can also be used "later", after another LOCK, like in > > your example in 5/7. > > I am fine either way. But there was an objection to tying this to the > unlock because it costs more on many architectures than tying this to > the lock. OK, I see, thanks. > But if you are saying "in addition to" rather than "instead of" that > would be a different conversation. Yes, please forget for now. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
