linux-kernel - Re: [PATCH 2/2] mm: replace TIF_MEMDIE checks by tsk_is_oom

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Message-Id: <201707272301.EII82876.tOOJOFLMHFQSFV@I-love.SAKURA.ne.jp>
Date:   Thu, 27 Jul 2017 23:01:05 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     mhocko@...nel.org, akpm@...ux-foundation.org
Cc:     rientjes@...gle.com, hannes@...xchg.org, guro@...com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org, mhocko@...e.com
Subject: Re: [PATCH 2/2] mm: replace TIF_MEMDIE checks by tsk_is_oom_victim

Michal Hocko wrote:
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 544d47e5cbbd..86a48affb938 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1896,7 +1896,7 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
>  	 * bypass the last charges so that they can exit quickly and
>  	 * free their memory.
>  	 */
> -	if (unlikely(test_thread_flag(TIF_MEMDIE) ||
> +	if (unlikely(tsk_is_oom_victim(current) ||
>  		     fatal_signal_pending(current) ||
>  		     current->flags & PF_EXITING))
>  		goto force;

Did we check http://lkml.kernel.org/r/20160909140508.GO4844@dhcp22.suse.cz ?

> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index c9f3569a76c7..65cc2f9aaa05 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -483,7 +483,7 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
>  	 *				[...]
>  	 *				out_of_memory
>  	 *				  select_bad_process
> -	 *				    # no TIF_MEMDIE task selects new victim
> +	 *				    # no TIF_MEMDIE, selects new victim
>  	 *  unmap_page_range # frees some memory
>  	 */
>  	mutex_lock(&oom_lock);

This comment is wrong. No MMF_OOM_SKIP mm selects new victim.