From: Oleg Nesterov <oleg@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
David Rientjes <rientjes@google.com>,
Vladimir Davydov <vdavydov@parallels.com>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH 1/6] proc, oom: drop bogus task_lock and mm check
Date: Mon, 30 May 2016 19:43:24 +0200 [thread overview]
Message-ID: <20160530174324.GA25382@redhat.com> (raw)
In-Reply-To: <1464613556-16708-2-git-send-email-mhocko@kernel.org>
On 05/30, Michal Hocko wrote:
>
> both oom_adj_write and oom_score_adj_write are using task_lock,
> check for task->mm and fail if it is NULL. This is not needed because
> the oom_score_adj is per signal struct so we do not need mm at all.
> The code has been introduced by 3d5992d2ac7d ("oom: add per-mm oom
> disable count") but we do not do per-mm oom disable since c9f01245b6a7
> ("oom: remove oom_disable_count").
>
> The task->mm check is even not correct because the current thread might
> have exited but the thread group might be still alive - e.g. thread
> group leader would lead that echo $VAL > /proc/pid/oom_score_adj would
> always fail with EINVAL while /proc/pid/task/$other_tid/oom_score_adj
> would succeed. This is unexpected at best.
>
> Remove the lock along with the check to fix the unexpected behavior
> and also because there is not real need for the lock in the first place.
ACK
and we should also remove lock_task_sighand(). as for oom_adj_read() and
oom_score_adj_read() we can just remove it right now; it was previously
needed to ensure the task->signal != NULL, today this is always true.
Oleg.
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WARNING: multiple messages have this Message-ID (diff)
From: Oleg Nesterov <oleg@redhat.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: linux-mm@kvack.org,
Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
David Rientjes <rientjes@google.com>,
Vladimir Davydov <vdavydov@parallels.com>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH 1/6] proc, oom: drop bogus task_lock and mm check
Date: Mon, 30 May 2016 19:43:24 +0200 [thread overview]
Message-ID: <20160530174324.GA25382@redhat.com> (raw)
In-Reply-To: <1464613556-16708-2-git-send-email-mhocko@kernel.org>
On 05/30, Michal Hocko wrote:
>
> both oom_adj_write and oom_score_adj_write are using task_lock,
> check for task->mm and fail if it is NULL. This is not needed because
> the oom_score_adj is per signal struct so we do not need mm at all.
> The code has been introduced by 3d5992d2ac7d ("oom: add per-mm oom
> disable count") but we do not do per-mm oom disable since c9f01245b6a7
> ("oom: remove oom_disable_count").
>
> The task->mm check is even not correct because the current thread might
> have exited but the thread group might be still alive - e.g. thread
> group leader would lead that echo $VAL > /proc/pid/oom_score_adj would
> always fail with EINVAL while /proc/pid/task/$other_tid/oom_score_adj
> would succeed. This is unexpected at best.
>
> Remove the lock along with the check to fix the unexpected behavior
> and also because there is not real need for the lock in the first place.
ACK
and we should also remove lock_task_sighand(). as for oom_adj_read() and
oom_score_adj_read() we can just remove it right now; it was previously
needed to ensure the task->signal != NULL, today this is always true.
Oleg.
next prev parent reply other threads:[~2016-05-30 17:43 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-30 13:05 [PATCH 0/6 -v2] Handle oom bypass more gracefully Michal Hocko
2016-05-30 13:05 ` Michal Hocko
2016-05-30 13:05 ` [PATCH 1/6] proc, oom: drop bogus task_lock and mm check Michal Hocko
2016-05-30 13:05 ` Michal Hocko
2016-05-30 13:49 ` Vladimir Davydov
2016-05-30 13:49 ` Vladimir Davydov
2016-05-30 17:43 ` Oleg Nesterov [this message]
2016-05-30 17:43 ` Oleg Nesterov
2016-05-31 7:32 ` Michal Hocko
2016-05-31 7:32 ` Michal Hocko
2016-05-31 22:53 ` Oleg Nesterov
2016-05-31 22:53 ` Oleg Nesterov
2016-06-01 6:53 ` Michal Hocko
2016-06-01 6:53 ` Michal Hocko
2016-06-01 10:41 ` Tetsuo Handa
2016-06-01 10:41 ` Tetsuo Handa
2016-06-01 10:48 ` Michal Hocko
2016-06-01 10:48 ` Michal Hocko
2016-05-30 13:05 ` [PATCH 2/6] proc, oom_adj: extract oom_score_adj setting into a helper Michal Hocko
2016-05-30 13:05 ` Michal Hocko
2016-05-30 13:05 ` [PATCH 3/6] mm, oom_adj: make sure processes sharing mm have same view of oom_score_adj Michal Hocko
2016-05-30 13:05 ` Michal Hocko
2016-05-31 7:41 ` Michal Hocko
2016-05-31 7:41 ` Michal Hocko
2016-05-30 13:05 ` [PATCH 4/6] mm, oom: skip vforked tasks from being selected Michal Hocko
2016-05-30 13:05 ` Michal Hocko
2016-05-30 19:28 ` Oleg Nesterov
2016-05-30 19:28 ` Oleg Nesterov
2016-05-31 7:42 ` Michal Hocko
2016-05-31 7:42 ` Michal Hocko
2016-05-31 21:43 ` Oleg Nesterov
2016-05-31 21:43 ` Oleg Nesterov
2016-06-01 7:09 ` Michal Hocko
2016-06-01 7:09 ` Michal Hocko
2016-06-01 14:12 ` Tetsuo Handa
2016-06-01 14:25 ` Michal Hocko
2016-06-02 10:45 ` Tetsuo Handa
2016-06-02 11:20 ` Michal Hocko
2016-06-02 11:31 ` Tetsuo Handa
2016-06-02 12:55 ` Michal Hocko
2016-05-30 13:05 ` [PATCH 5/6] mm, oom: kill all tasks sharing the mm Michal Hocko
2016-05-30 13:05 ` Michal Hocko
2016-05-30 18:18 ` Oleg Nesterov
2016-05-30 18:18 ` Oleg Nesterov
2016-05-31 7:43 ` Michal Hocko
2016-05-31 7:43 ` Michal Hocko
2016-05-31 21:48 ` Oleg Nesterov
2016-05-31 21:48 ` Oleg Nesterov
2016-05-30 13:05 ` [PATCH 6/6] mm, oom: fortify task_will_free_mem Michal Hocko
2016-05-30 13:05 ` Michal Hocko
2016-05-30 17:35 ` Oleg Nesterov
2016-05-30 17:35 ` Oleg Nesterov
2016-05-31 7:46 ` Michal Hocko
2016-05-31 7:46 ` Michal Hocko
2016-05-31 22:29 ` Oleg Nesterov
2016-05-31 22:29 ` Oleg Nesterov
2016-06-01 7:03 ` Michal Hocko
2016-06-01 7:03 ` Michal Hocko
2016-05-31 15:03 ` Tetsuo Handa
2016-05-31 15:10 ` Michal Hocko
2016-05-31 15:29 ` Tetsuo Handa
2016-06-01 7:25 ` Michal Hocko
2016-06-01 12:04 ` Tetsuo Handa
2016-06-01 12:43 ` Michal Hocko
2016-06-02 14:03 ` [PATCH 7/6] mm, oom: task_will_free_mem should skip oom_reaped tasks Michal Hocko
2016-06-02 14:03 ` Michal Hocko
2016-06-02 15:24 ` Tetsuo Handa
2016-06-02 15:50 ` Michal Hocko
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