linux-kernel - Re: [PATCH] sched/deadline: fix rq->dl.pushable_tasks bug in push_dl

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Date:	Tue, 11 Nov 2014 15:44:06 +0800
From:	Wanpeng Li <kernellwp@...il.com>
To:	Wanpeng Li <wanpeng.li@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@....com>
CC:	Kirill Tkhai <ktkhai@...allels.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/deadline: fix rq->dl.pushable_tasks bug in push_dl_task()

Ping Juri, could you review this one and other deadline patches of mine? 
;-)
On 14/11/6 下午3:22, Wanpeng Li wrote:
> Do not call dequeue_pushable_dl_task() when failing to push an eligible
> task, as it remains pushable, merely not at this particular moment.
> Actually the patch is the same behavior as commit 311e800e16f6 ("sched,
> rt: Fix rq->rt.pushable_tasks bug in push_rt_task()" in -rt side.
>
> Signed-off-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
> ---
>   kernel/sched/deadline.c | 5 +++--
>   1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index f3d7776..00324af 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -1331,6 +1331,7 @@ static int push_dl_task(struct rq *rq)
>   {
>   	struct task_struct *next_task;
>   	struct rq *later_rq;
> +	int ret = 0;
>   
>   	if (!rq->dl.overloaded)
>   		return 0;
> @@ -1376,7 +1377,6 @@ retry:
>   			 * The task is still there. We don't try
>   			 * again, some other cpu will pull it when ready.
>   			 */
> -			dequeue_pushable_dl_task(rq, next_task);
>   			goto out;
>   		}
>   
> @@ -1392,6 +1392,7 @@ retry:
>   	deactivate_task(rq, next_task, 0);
>   	set_task_cpu(next_task, later_rq->cpu);
>   	activate_task(later_rq, next_task, 0);
> +	ret = 1;
>   
>   	resched_curr(later_rq);
>   
> @@ -1400,7 +1401,7 @@ retry:
>   out:
>   	put_task_struct(next_task);
>   
> -	return 1;
> +	return ret;
>   }
>   
>   static void push_dl_tasks(struct rq *rq)

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