From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Andrew Morton <akpm@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>
Cc: David Rientjes <rientjes@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Yong-Taek Lee <ytk.lee@samsung.com>,
linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>,
Michal Hocko <mhocko@suse.com>
Subject: Re: [PATCH] proc, oom: do not report alien mms when setting oom_score_adj
Date: Wed, 13 Feb 2019 06:07:26 +0900 [thread overview]
Message-ID: <46b3262e-2a9a-da01-16de-14cd4d7eaa40@i-love.sakura.ne.jp> (raw)
In-Reply-To: <20190212125635.27742b5741e92a0d47690c53@linux-foundation.org>
On 2019/02/13 5:56, Andrew Morton wrote:
> On Tue, 12 Feb 2019 11:21:29 +0100 Michal Hocko <mhocko@kernel.org> wrote:
>
>> Tetsuo has reported that creating a thousands of processes sharing MM
>> without SIGHAND (aka alien threads) and setting
>> /proc/<pid>/oom_score_adj will swamp the kernel log and takes ages [1]
>> to finish. This is especially worrisome that all that printing is done
>> under RCU lock and this can potentially trigger RCU stall or softlockup
>> detector.
>>
>> The primary reason for the printk was to catch potential users who might
>> depend on the behavior prior to 44a70adec910 ("mm, oom_adj: make sure
>> processes sharing mm have same view of oom_score_adj") but after more
>> than 2 years without a single report I guess it is safe to simply remove
>> the printk altogether.
>>
>> The next step should be moving oom_score_adj over to the mm struct and
>> remove all the tasks crawling as suggested by [2]
>>
>> [1] http://lkml.kernel.org/r/97fce864-6f75-bca5-14bc-12c9f890e740@i-love.sakura.ne.jp
>> [2] http://lkml.kernel.org/r/20190117155159.GA4087@dhcp22.suse.cz
>
> I think I'll put a cc:stable on this. Deleting a might-trigger debug
> printk is safe and welcome.
>
Putting cc:stable is fine. But I doubt the usefulness of this patch.
If nobody really depends on the behavior prior to 44a70adec910,
we should remove the pointless (otherwise racy) iteration itself.
next prev parent reply other threads:[~2019-02-12 21:07 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-12 10:21 [PATCH] proc, oom: do not report alien mms when setting oom_score_adj Michal Hocko
2019-02-12 16:08 ` Johannes Weiner
2019-02-12 20:56 ` Andrew Morton
2019-02-12 21:07 ` Tetsuo Handa [this message]
2019-02-13 1:24 ` Tetsuo Handa
2019-02-13 11:47 ` Michal Hocko
2019-02-15 0:57 ` Tetsuo Handa
2019-02-15 9:37 ` Michal Hocko
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