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From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: mhocko@kernel.org, linux-mm@kvack.org
Cc: rientjes@google.com, oleg@redhat.com, vdavydov@parallels.com,
	akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	mhocko@suse.com
Subject: Re: [PATCH 10/10] mm, oom: hide mm which is shared with kthread or global init
Date: Fri, 10 Jun 2016 00:15:18 +0900	[thread overview]
Message-ID: <201606100015.HBB65678.LSOFFJOFMQHOVt@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <1465473137-22531-11-git-send-email-mhocko@kernel.org>

Michal Hocko wrote:
> The only case where the oom_reaper is not triggered for the oom victim
> is when it shares the memory with a kernel thread (aka use_mm) or with
> the global init. After "mm, oom: skip vforked tasks from being selected"
> the victim cannot be a vforked task of the global init so we are left
> with clone(CLONE_VM) (without CLONE_SIGHAND). use_mm() users are quite
> rare as well.

CONFIG_MMU=n is the other case where the oom_reaper is not triggered for
the oom victim.

> 
> In order to guarantee a forward progress for the OOM killer make
> sure that this really rare cases will not get into the way and hide
> the mm from the oom killer by setting MMF_OOM_REAPED flag for it.
> oom_scan_process_thread will ignore any TIF_MEMDIE task if it has
> MMF_OOM_REAPED flag set to catch these oom victims.

Nobody will set MMF_OOM_REAPED flag if can_oom_reap == true on
CONFIG_MMU=n kernel. If a TIF_MEMDIE thread in CONFIG_MMU=n kernel
is blocked before exit_oom_victim() in exit_mm() from do_exit() is
called, the system will lock up. This is not handled in the patch
nor explained in the changelog.

> 
> After this patch we should guarantee a forward progress for the OOM
> killer even when the selected victim is sharing memory with a kernel
> thread or global init.

  reply	other threads:[~2016-06-09 15:15 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-09 11:52 [PATCH 0/10 -v4] Handle oom bypass more gracefully Michal Hocko
2016-06-09 11:52 ` [PATCH 01/10] proc, oom: drop bogus task_lock and mm check Michal Hocko
2016-06-09 11:52 ` [PATCH 02/10] proc, oom: drop bogus sighand lock Michal Hocko
2016-06-09 11:52 ` [PATCH 03/10] proc, oom_adj: extract oom_score_adj setting into a helper Michal Hocko
2016-06-09 11:52 ` [PATCH 04/10] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Michal Hocko
2016-06-15 15:03   ` Oleg Nesterov
2016-06-09 11:52 ` [PATCH 05/10] mm, oom: skip vforked tasks from being selected Michal Hocko
2016-06-15 14:51   ` Oleg Nesterov
2016-06-16  6:24     ` Michal Hocko
2016-06-09 11:52 ` [PATCH 06/10] mm, oom: kill all tasks sharing the mm Michal Hocko
2016-06-09 11:52 ` [PATCH 07/10] mm, oom: fortify task_will_free_mem Michal Hocko
2016-06-09 13:18   ` Tetsuo Handa
2016-06-09 14:20     ` Michal Hocko
2016-06-11  8:10       ` Tetsuo Handa
2016-06-13 11:27         ` Michal Hocko
2016-06-16 12:54           ` Tetsuo Handa
2016-06-16 14:29             ` Michal Hocko
2016-06-16 15:40               ` Tetsuo Handa
2016-06-16 15:53                 ` Michal Hocko
2016-06-17 11:38                   ` Tetsuo Handa
2016-06-17 12:26                     ` Michal Hocko
2016-06-17 13:12                       ` Tetsuo Handa
2016-06-17 13:29                         ` Michal Hocko
2016-06-09 11:52 ` [PATCH 08/10] mm, oom: task_will_free_mem should skip oom_reaped tasks Michal Hocko
2016-06-17 11:35   ` Tetsuo Handa
2016-06-17 12:56     ` Michal Hocko
2016-06-09 11:52 ` [PATCH 09/10] mm, oom_reaper: do not attempt to reap a task more than twice Michal Hocko
2016-06-15 14:48   ` Oleg Nesterov
2016-06-16  6:28     ` Michal Hocko
2016-06-09 11:52 ` [PATCH 10/10] mm, oom: hide mm which is shared with kthread or global init Michal Hocko
2016-06-09 15:15   ` Tetsuo Handa [this message]
2016-06-09 15:41     ` Michal Hocko
2016-06-16 13:15       ` Tetsuo Handa
2016-06-16 13:36         ` Tetsuo Handa
2016-06-15 14:37   ` Oleg Nesterov
2016-06-16  6:31     ` Michal Hocko
2016-06-13 11:23 ` [PATCH 0/10 -v4] Handle oom bypass more gracefully Michal Hocko
2016-06-13 14:13   ` Michal Hocko
2016-06-14 20:17     ` Oleg Nesterov
2016-06-14 20:44       ` Oleg Nesterov
2016-06-16  6:33       ` Michal Hocko
2016-06-15 15:09 ` Oleg Nesterov
2016-06-16  6:34   ` Michal Hocko
2016-06-20 12:43 [PATCH 0/10 -v5] " Michal Hocko
2016-06-20 12:43 ` [PATCH 10/10] mm, oom: hide mm which is shared with kthread or global init Michal Hocko
2016-07-19 12:05   ` Michal Hocko
2016-07-19 23:27     ` Andrew Morton
2016-07-20  6:29       ` Michal Hocko

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