linux-kernel - Re: [PATCH] sched: fix rt_nr_migratory corruption raised in push_rt

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Message-ID: <BANLkTi=YXK7pCJqei6oz4dzLzHgJC_m=2g@mail.gmail.com>
Date:	Tue, 31 May 2011 21:56:39 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	Mike Galbraith <efault@....de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Yong Zhang <yong.zhang0@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] sched: fix rt_nr_migratory corruption raised in push_rt_task()

On Tue, May 31, 2011 at 3:36 PM, Mike Galbraith <efault@....de> wrote:
> On Mon, 2011-05-30 at 21:39 +0800, Hillf Danton wrote:
>> When pushing, if a pushable task could not be pushed, it is dequeued with no
>> updating the rt_nr_migratory element of RT run-queue, then rt_nr_migratory is
>> corrupted, which is fixed by removing the dequeue operation.
>
> Hm.  I think you're right that this dequeue_pushable_task() call can be
> removed, at least I didn't see it's reason for existing.  I'd word it a
> bit differently though, and not return 1 unless we really did push.
>

Hi Mike

Your message shows what is called professional work, but something lost,

> From: Hillf Danton <dhillf@...il.com>
>
> sched, rt: fix rq->rt.pushable_tasks bug in push_rt_task()
>
> Do not call dequeue_pushable_task() when failing to push an eligible
> task, as it remains pushable, merely not at this particular moment.
>
> Signed-off-by: Hillf Danton <dhillf@...il.com>

Signed-off-by: Mike Galbraith <efault@....de>

right?

> ---
>  kernel/sched_rt.c |   15 ++++++++-------
>  1 file changed, 8 insertions(+), 7 deletions(-)
>
> Index: linux-2.6.40.git/kernel/sched_rt.c
> ===================================================================

And how to drive git to print the above two lines?

thanks
            Hillf
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