Re: [PATCH 3/8] sched/wait: Use __add_wait_queue{_tail}_exclusive() as possible.

[Dongsheng Yang]

On 04/15/2014 10:49 PM, Peter Zijlstra wrote:
> On Tue, Apr 15, 2014 at 09:32:52PM +0900, Dongsheng Yang wrote:
> > From: Dongsheng <yangds.fnst@xxxxxxxxxxxxxx>
> >
> > There is already a function in include/linux/wait.h to cover the
> > 'exclusive' usage. So we can use it in sched/wait.c to replace
> > the opened implementation of it.
> >
> > Signed-off-by: Dongsheng <yangds.fnst@xxxxxxxxxxxxxx>
> > ---
> >   kernel/sched/wait.c | 6 ++----
> >   1 file changed, 2 insertions(+), 4 deletions(-)
> >
> > diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
> > index 283750e..b04827e 100644
> > --- a/kernel/sched/wait.c
> > +++ b/kernel/sched/wait.c
> > @@ -38,9 +38,8 @@ void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait)
> >   	unsigned long flags;
> >   
> >   	trace_sched_wait(current);
> > -	wait->flags |= WQ_FLAG_EXCLUSIVE;
> >   	spin_lock_irqsave(&q->lock, flags);
> > -	__add_wait_queue_tail(q, wait);
> > +	__add_wait_queue_tail_exclusive(q, wait);
> >   	spin_unlock_irqrestore(&q->lock, flags);
> >   }
> >   EXPORT_SYMBOL(add_wait_queue_exclusive);
> > @@ -192,10 +191,9 @@ prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state)
> >   	unsigned long flags;
> >   
> >   	trace_sched_wait(current);
> > -	wait->flags |= WQ_FLAG_EXCLUSIVE;
> >   	spin_lock_irqsave(&q->lock, flags);
> >   	if (list_empty(&wait->task_list))
> > -		__add_wait_queue_tail(q, wait);
> > +		__add_wait_queue_tail_exclusive(q, wait);
> >   	set_current_state(state);
> >   	spin_unlock_irqrestore(&q->lock, flags);
> That is not a no-op, if !list_empty() we loose the WQ_flag

Oh, yes, my mistake. Thanx
> .

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