From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
To: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH v3] mm: memcontrol: fix potential oom_lock recursion deadlock
Date: Fri, 22 Jul 2022 20:12:31 +0900 [thread overview]
Message-ID: <d1feb1b4-d7bb-0e7a-ae06-1adeb12b9c02@I-love.SAKURA.ne.jp> (raw)
In-Reply-To: <YtqEJToMl+uos+Td@dhcp22.suse.cz>
On 2022/07/22 20:04, Michal Hocko wrote:
> On Fri 22-07-22 19:45:39, Tetsuo Handa wrote:
>> syzbot is reporting GFP_KERNEL allocation with oom_lock held when reporting
>> memcg OOM [1]. Such allocation request might deadlock the system, for
>> __alloc_pages_may_oom() cannot invoke global OOM killer due to oom_lock
>> being already held by the caller.
>
> OK, I have misunderstood your previous wording and now I have realized
> that there are 2 issues here. One of them is a (less likely) dead lock on
> the oom_lock not making a fwd progress (that would require global OOM
> racing with memcg OOM) and the other is the GFP_NOFS->GFP_KERNEL dependency
> which can deadlock even without global the above race.
> Correct?
Correct.
>
> Sorry I could have realized that sooner.
>
No problem. Thanks for suggestion.
prev parent reply other threads:[~2022-07-22 11:12 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <000000000000471c2905e3c2c2c2@google.com>
2022-07-14 14:18 ` [syzbot] possible deadlock in start_this_handle (3) Jan Kara
[not found] ` <534fa596-0c29-0f1e-b292-53ad9c3dbbe3@I-love.SAKURA.ne.jp>
2022-07-15 1:39 ` Shakeel Butt
[not found] ` <03304bf8-d153-698f-0376-9e9a0ec1048e@I-love.SAKURA.ne.jp>
2022-07-20 23:49 ` [PATCH] mm: memcontrol: fix potential oom_lock recursion deadlock Tetsuo Handa
2022-07-21 8:01 ` Michal Hocko
2022-07-22 0:46 ` [PATCH v2] " Tetsuo Handa
2022-07-22 7:19 ` Michal Hocko
2022-07-22 10:45 ` [PATCH v3] " Tetsuo Handa
2022-07-22 11:04 ` Michal Hocko
2022-07-22 11:12 ` Tetsuo Handa [this message]
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