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[37.188.169.187]) by smtp.gmail.com with ESMTPSA id m2sm30929496wmg.0.2020.07.20.00.16.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jul 2020 00:16:08 -0700 (PDT) Date: Mon, 20 Jul 2020 09:16:07 +0200 From: Michal Hocko To: Yafang Shao Cc: rientjes@google.com, penguin-kernel@i-love.sakura.ne.jp, akpm@linux-foundation.org, linux-mm@kvack.org Subject: Re: [PATCH] mm, oom: show process exiting information in __oom_kill_process() Message-ID: <20200720071607.GA18535@dhcp22.suse.cz> References: <1595166795-27587-1-git-send-email-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1595166795-27587-1-git-send-email-laoar.shao@gmail.com> X-Rspamd-Queue-Id: 4B3A610062CB3 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Sun 19-07-20 09:53:15, Yafang Shao wrote: > When the OOM killer finding a victim and trying to kill it, if the victim > is already exiting, the task mm will be NULL and no process will be killed. > But the dump_header() has been already executed, so it will be strange to > dump so many information without killing a process. We'd better show some > helpful information to indicate why this happens. > > Suggested-by: David Rientjes > Signed-off-by: Yafang Shao > Cc: Michal Hocko > Cc: Tetsuo Handa > --- > mm/oom_kill.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > index 6e94962..0480dde 100644 > --- a/mm/oom_kill.c > +++ b/mm/oom_kill.c > @@ -863,9 +863,13 @@ static void __oom_kill_process(struct task_struct *victim, const char *message) > > p = find_lock_task_mm(victim); > if (!p) { > + pr_info("Process %d (%s) is already exiting\n", > + task_pid_nr(victim), victim->comm); > put_task_struct(victim); I do agree that a silent bail out is not the best thing to do. The above message would be more useful if it also explained what the oom killer does (or does not): "OOM victim %d (%s) is already exiting. Skip killing the task\n" > return; > - } else if (victim != p) { > + } > + > + if (victim != p) { Why do we need this? > get_task_struct(p); > put_task_struct(victim); > victim = p; > -- > 1.8.3.1 -- Michal Hocko SUSE Labs