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Subject: Re: [RFC] Getting rid of INFLIGHT_VICTIM
From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
References: <10e40484-66e2-d879-e9b7-f50fdc5846ac@i-love.sakura.ne.jp>
Message-ID: <8da59f92-8de5-99e9-c62e-c972e2a66ac4@i-love.sakura.ne.jp>
Date: Tue, 5 Jun 2018 23:10:20 +0900
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Sender: owner-linux-mm@kvack.org
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To: Michal Hocko <mhocko@kernel.org>, David Rientjes <rientjes@google.com>, Roman Gushchin <guro@fb.com>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>, Johannes Weiner <hannes@cmpxchg.org>, Andrew Morton <akpm@linux-foundation.org>, Tejun Heo <tj@kernel.org>, linux-mm <linux-mm@kvack.org>

On 2018/06/05 22:31, Tetsuo Handa wrote:
> @@ -639,15 +618,18 @@ static int oom_reaper(void *unused)
>  
>  static void wake_oom_reaper(struct task_struct *tsk)
>  {
> -	/* tsk is already queued? */
> -	if (tsk == oom_reaper_list || tsk->oom_reaper_list)
> -		return;
> -
> -	get_task_struct(tsk);
> +	struct task_struct *p = oom_reaper_th;
>  
>  	spin_lock(&oom_reaper_lock);
> -	tsk->oom_reaper_list = oom_reaper_list;
> -	oom_reaper_list = tsk;
> +	while (p != tsk && p->oom_reaper_list)
> +		p = p->oom_reaper_list;
> +	if (p != tsk) {

Oops. This is "if (p == tsk) {".

> +		spin_unlock(&oom_reaper_lock);
> +		return;
> +	}
> +	p->oom_reaper_list = tsk;
> +	tsk->oom_reaper_list = NULL;
> +	get_task_struct(tsk);
>  	spin_unlock(&oom_reaper_lock);
>  	trace_wake_reaper(tsk->pid);
>  	wake_up(&oom_reaper_wait);