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Subject: Re: [RFC 1/2] mm: oom: expose expedite_reclaim to use oom_reaper
 outside of oom_kill.c
To:     Suren Baghdasaryan <surenb@google.com>
Cc:     akpm@linux-foundation.org, mhocko@suse.com, rientjes@google.com,
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        lsf-pc@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        kernel-team@android.com
References: <20190411014353.113252-1-surenb@google.com>
 <20190411014353.113252-2-surenb@google.com>
From:   Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Message-ID: <c745df86-b95c-e82b-42ba-519da4f448ab@i-love.sakura.ne.jp>
Date:   Fri, 26 Apr 2019 06:12:27 +0900
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On 2019/04/11 10:43, Suren Baghdasaryan wrote:
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 3a2484884cfd..6449710c8a06 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -1102,6 +1102,21 @@ bool out_of_memory(struct oom_control *oc)
>  	return !!oc->chosen;
>  }
>  
> +bool expedite_reclaim(struct task_struct *task)
> +{
> +	bool res = false;
> +
> +	task_lock(task);
> +	if (task_will_free_mem(task)) {

mark_oom_victim() needs to be called under oom_lock mutex after
checking that oom_killer_disabled == false. Since you are trying
to trigger this function from signal handler, you might want to
defer until e.g. WQ context.

> +		mark_oom_victim(task);
> +		wake_oom_reaper(task);
> +		res = true;
> +	}
> +	task_unlock(task);
> +
> +	return res;
> +}
> +
>  /*
>   * The pagefault handler calls here because it is out of memory, so kill a
>   * memory-hogging task. If oom_lock is held by somebody else, a parallel oom
>