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SubjectRe: [PATCH 3/8] sched/wait: Use __add_wait_queue{_tail}_exclusive() as possible.
On Tue, Apr 15, 2014 at 09:32:52PM +0900, Dongsheng Yang wrote:
> From: Dongsheng <yangds.fnst@cn.fujitsu.com>
>
> 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@cn.fujitsu.com>
> ---
> 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


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