Messages in this thread | | | Subject | Re: [PATCH v1 3/8] sched/completion: convert completions to use simple wait queues | From | Daniel Wagner <> | Date | Mon, 12 Oct 2015 11:17:14 +0200 |
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On 09/09/2015 04:26 PM, Peter Zijlstra wrote: > On Wed, Sep 09, 2015 at 02:05:29PM +0200, Daniel Wagner wrote: >> @@ -50,10 +50,10 @@ void complete_all(struct completion *x) >> { >> unsigned long flags; >> >> - spin_lock_irqsave(&x->wait.lock, flags); >> + raw_spin_lock_irqsave(&x->wait.lock, flags); >> x->done += UINT_MAX/2; >> - __wake_up_locked(&x->wait, TASK_NORMAL, 0); >> - spin_unlock_irqrestore(&x->wait.lock, flags); >> + swake_up_locked(&x->wait); >> + raw_spin_unlock_irqrestore(&x->wait.lock, flags); >> } >> EXPORT_SYMBOL(complete_all); > > I don't think that's correct; __wake_up_locked(.nr=0) would wake all > waiters, where swake_up_locked() will only wake one.
I read that x->done should be protected via wait.lock during the whole operation. swake_up_all() will release and reacquire the lock while processing the all waiters. So we need to get
Could we play a trick like setting the highest bit in done for indicating the complete_all() operation. The UINT_MAX/2 update looks like do this by setting a value which has the biggest offset from 0 (but why adding instead of just going for assigning...).
cheers, daniel
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