lkml.org 
[lkml]   [2015]   [Oct]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v1 3/8] sched/completion: convert completions to use simple wait queues
From
Date
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



\
 
 \ /
  Last update: 2015-10-12 11:41    [W:0.103 / U:0.276 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site