From: Oleg Nesterov <oleg@redhat.com>
To: Sameer Nanda <snanda@chromium.org>
Cc: akpm@linux-foundation.org, mhocko@suse.cz, rientjes@google.com,
hannes@cmpxchg.org, rusty@rustcorp.com.au, semenzato@google.com,
murzin.v@gmail.com, dserrg@gmail.com, msb@chromium.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4] mm, oom: Fix race when selecting process to kill
Date: Tue, 12 Nov 2013 21:01:56 +0100 [thread overview]
Message-ID: <20131112200156.GA9820@redhat.com> (raw)
In-Reply-To: <1384215717-2389-1-git-send-email-snanda@chromium.org>
On 11/11, Sameer Nanda wrote:
>
> The selection of the process to be killed happens in two spots:
> first in select_bad_process and then a further refinement by
> looking for child processes in oom_kill_process. Since this is
> a two step process, it is possible that the process selected by
> select_bad_process may get a SIGKILL just before oom_kill_process
> executes. If this were to happen, __unhash_process deletes this
> process from the thread_group list. This results in oom_kill_process
> getting stuck in an infinite loop when traversing the thread_group
> list of the selected process.
>
> Fix this race by adding a pid_alive check for the selected process
> with tasklist_lock held in oom_kill_process.
OK, looks correct to me. Thanks.
Yes, this is a step backwards, hopefully we will revert this patch soon.
I am starting to think something like while_each_thread_lame_but_safe()
makes sense before we really fix this nasty (and afaics not simple)
problem with with while_each_thread() (which should die).
Oleg.
next prev parent reply other threads:[~2013-11-12 20:00 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-05 23:26 [PATCH] mm, oom: Fix race when selecting process to kill Sameer Nanda
2013-11-06 1:18 ` David Rientjes
2013-11-06 1:25 ` Luigi Semenzato
2013-11-06 1:27 ` David Rientjes
2013-11-06 3:00 ` Vladimir Murzin
[not found] ` <CANMivWZrefY1bbgpJgABqcUwKfqOR9HQtGNY6cWdutcMASeo2A@mail.gmail.com>
2013-11-06 4:45 ` Luigi Semenzato
2013-11-06 7:17 ` Luigi Semenzato
2013-11-06 16:58 ` Sameer Nanda
2013-11-07 0:35 ` David Rientjes
2013-11-07 19:34 ` Sameer Nanda
2013-11-08 18:07 ` [PATCH v2] " Sameer Nanda
2013-11-08 18:45 ` Oleg Nesterov
2013-11-08 19:49 ` [PATCH v3] " Sameer Nanda
2013-11-09 15:16 ` Oleg Nesterov
2013-11-12 0:21 ` [PATCH v4] " Sameer Nanda
2013-11-12 15:13 ` Michal Hocko
2013-11-12 20:01 ` Oleg Nesterov [this message]
2013-11-12 20:08 ` Sameer Nanda
2013-11-12 20:23 ` [PATCH v5] " Sameer Nanda
2013-11-13 2:33 ` David Rientjes
2013-11-13 16:46 ` Sameer Nanda
2013-11-13 17:18 ` [PATCH v6] " Sameer Nanda
2013-11-13 17:29 ` Oleg Nesterov
[not found] ` <CAMw+i9hi9pBPkfWHo3mh0=PATQFzbNOCSPaLkw+zqUvwK2wbxA@mail.gmail.com>
2013-11-14 17:03 ` Sameer Nanda
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