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

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Message-Id: <201707272308.GHD90652.OSHQtOOVJFLFMF@I-love.SAKURA.ne.jp>
Date:   Thu, 27 Jul 2017 23:08:42 +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

Tetsuo Handa wrote:
> 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.
> 
Oops. "MMF_OOM_SKIP mm selects new victim." according to
http://lkml.kernel.org/r/201706271952.FEB21375.SFJFHOQLOtVOMF@I-love.SAKURA.ne.jp .