Messages in this thread | | | Subject | Re: Warning from swake_up_all in 4.14.15-rt13 non-RT | From | Corey Minyard <> | Date | Fri, 9 Mar 2018 16:02:42 -0600 |
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On 03/09/2018 11:46 AM, Peter Zijlstra wrote: > On Fri, Mar 09, 2018 at 12:04:18PM +0100, Sebastian Andrzej Siewior wrote: >> +void swake_add_all_wq(struct swait_queue_head *q, struct wake_q_head *wq) >> { >> struct swait_queue *curr; >> >> while (!list_empty(&q->task_list)) { >> >> curr = list_first_entry(&q->task_list, typeof(*curr), >> task_list); >> list_del_init(&curr->task_list); >> + wake_q_add(wq, curr->task); >> } >> } >> +EXPORT_SYMBOL(swake_add_all_wq); >> >> void swake_up(struct swait_queue_head *q) >> { >> @@ -66,25 +62,14 @@ EXPORT_SYMBOL(swake_up); >> */ >> void swake_up_all(struct swait_queue_head *q) >> { >> + unsigned long flags; >> + DEFINE_WAKE_Q(wq); >> >> + raw_spin_lock_irqsave(&q->lock, flags); >> + swake_add_all_wq(q, &wq); >> + raw_spin_unlock_irqrestore(&q->lock, flags); >> >> + wake_up_q(&wq); >> } >> EXPORT_SYMBOL(swake_up_all); > This is fundamentally wrong. The whole point of wake_up_all() is that > _all_ is unbounded and should not ever land in a single critical > section, be it IRQ or PREEMPT disabled. The above does both.
It seems to me to be better than what was there, certainly more efficient.
And if I understand this correctly it is unbounded when !RT, but it is bounded on RT.
And I'm biased, because it should fix my problem :).
> Yes, wake_up_all() is crap, it is also fundamentally incompatible with > in-*irq usage. Nothing to be done about that. > > So NAK on this.
So what would you suggest? At this point getting rid of all the users of wake_up_all() from interrupt context is not really an option, though as an eventual goal it would be good.
-corey
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