Messages in this thread | | | Date | Thu, 1 Sep 2016 19:26:58 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH 1/2] sched/wait: abort_exclusive_wait() should pass TASK_NORMAL to wake_up() |
| |
On 09/01, Peter Zijlstra wrote: > > So mixing INTERRUPTIBLE and UNINTERRUPTIBLE and then not using > TASK_NORMAL for wakeups is a mis-feature/abuse of waitqueues IMO.
Heh, agreed. When I was doing this fix I suddenly realize that I do not understand why do we have, say, wake_up_interruptible().
I mean, I can't imagine the "real" use-case when you actually want to wake up only the INTERRUPTIBLE tasks and leave the UNINTERRUPTIBLE sleeping. Exclusive or not.
It seems that wake_up_interruptible() is mostly used simply because the caller knows that UNINTERRUPTIBLE waiters are not possible, this is often the case.
> @@ -67,6 +70,16 @@ static void __wake_up_common(wait_queue_head_t *q, unsigned int mode, > { > wait_queue_t *curr, *next; > > +#ifdef CONFIG_DEBUG_WAITQUEUE > + if (q->state != -1) { > + /* > + * WARN if we have INTERRUPTIBLE and UNINTERRUPTIBLE > + * waiters and do not use TASK_NORMAL to wake. > + */ > + WARN_ON_ONCE(q->state != (mode & TASK_NORMAL)); > + } > +#endif
Yes, perhaps...
Actually, I think that TASK_NORMAL should be used even if wq mixes UNINTERRUPTIBLE and KILLABLE waiters. The fact that TASK_KILLABLE includes TASK_UNINTERRUPTIBLE is just "implementation detail" even if I do not think this will be ever changed.
Oleg.
| |