linux-kernel - Re: [PATCH] Fix the issue that lowmemkiller fell into a cycle that try to kill a task

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Date:	Mon, 22 Sep 2014 21:17:38 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	Hui Zhu <zhuhui@...omi.com>
Cc:	rientjes@...gle.com, vinayakm.list@...il.com,
	weijie.yang@...sung.com, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org, teawater@...il.com
Subject: Re: [PATCH] Fix the issue that lowmemkiller fell into a cycle that
 try to kill a task

On Tue, Sep 23, 2014 at 10:57:09AM +0800, Hui Zhu wrote:
> The cause of this issue is when free memroy size is low and a lot of task is
> trying to shrink the memory, the task that is killed by lowmemkiller cannot get
> CPU to exit itself.
> 
> Fix this issue with change the scheduling policy to SCHED_FIFO if a task's flag
> is TIF_MEMDIE in lowmemkiller.
> 
> Signed-off-by: Hui Zhu <zhuhui@...omi.com>
> ---
>  drivers/staging/android/lowmemorykiller.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
> index b545d3d..ca1ffac 100644
> --- a/drivers/staging/android/lowmemorykiller.c
> +++ b/drivers/staging/android/lowmemorykiller.c
> @@ -129,6 +129,10 @@ static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
>  
>  		if (test_tsk_thread_flag(p, TIF_MEMDIE) &&
>  		    time_before_eq(jiffies, lowmem_deathpending_timeout)) {
> +			struct sched_param param = { .sched_priority = 1 };
> +
> +			if (p->policy == SCHED_NORMAL)
> +				sched_setscheduler(p, SCHED_FIFO, &param);

This seems really specific to a specific scheduler pattern now.  Isn't
there some other way to resolve this?

thanks,

greg k-h
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