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From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: Michal Hocko <mhocko@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	David Rientjes <rientjes@google.com>,
	syzbot <syzbot+f0fc7f62e88b1de99af3@syzkaller.appspotmail.com>,
	'Dmitry Vyukov' via syzkaller-upstream-moderation
	<syzkaller-upstream-moderation@googlegroups.com>,
	linux-mm <linux-mm@kvack.org>
Subject: Re: [PATCH] mm, oom: Introduce time limit for dump_tasks duration.
Date: Thu, 6 Sep 2018 20:25:19 +0900	[thread overview]
Message-ID: <1de89f00-42f7-16e3-e718-02fb9f125db1@i-love.sakura.ne.jp> (raw)
In-Reply-To: <CACT4Y+Zx6Jrpjfo_sDMNuHcrPvcN3GRprtJM_bCAts7f3Cp0_g@mail.gmail.com>

On 2018/09/06 20:07, Dmitry Vyukov wrote:
>> Since printk() is slow, printing one line takes nearly 0.01 second.
>> As a result, syzbot is stalling for 52 seconds trying to dump 5600
> 
> I wonder why there are so many of them?
> We have at most 8 test processes (each having no more than 16 threads
> if that matters).
> No more than 1 instance of syz-executor1 at a time. But we see output
> like the one below. It has lots of instances of syz-executor1 with
> different pid's. So does it print all tasks that ever existed (kernel
> does not store that info, right)? Or it livelocks picking up new and
> new tasks as they are created slower than they are created? Or we have
> tons of zombies?
> 
> ...

I don't think they are zombies. Since tasks which already released ->mm
are not printed, these tasks are still alive.

  [  pid  ]   uid  tgid total_vm      rss pgtables_bytes swapents oom_score_adj name
> [   8037]     0  8037    17618     8738   131072        0             0 syz-executor1

Maybe something signal / fork() / exit() / wait() related regression?

  reply	other threads:[~2018-09-06 12:24 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <0000000000004a6b700575178b5a@google.com>
     [not found] ` <CACT4Y+aPRGUqAdJCMDWM=Zcy8ZQcHyrsB1ZuWS4VB_+wvLfeaQ@mail.gmail.com>
2018-09-05 10:53   ` INFO: task hung in ext4_da_get_block_prep Tetsuo Handa
2018-09-05 11:06     ` Dmitry Vyukov
2018-09-06  5:53       ` Tetsuo Handa
2018-09-06  9:54         ` Dmitry Vyukov
2018-09-06 10:58           ` [PATCH] mm, oom: Introduce time limit for dump_tasks duration Tetsuo Handa
2018-09-06 11:07             ` Dmitry Vyukov
2018-09-06 11:25               ` Tetsuo Handa [this message]
2018-09-06 11:23             ` Michal Hocko
2018-09-06 11:40               ` Tetsuo Handa
2018-09-06 11:53                 ` Michal Hocko
2018-09-06 12:08                   ` Dmitry Vyukov
2018-09-06 12:16                     ` Michal Hocko
2018-09-11 16:37                       ` Oleg Nesterov
2018-09-12 16:45                         ` Oleg Nesterov
2018-09-06 13:45                   ` Tetsuo Handa
2018-09-06 14:39                     ` Michal Hocko
2018-09-06 20:58                       ` Tetsuo Handa
2018-09-07  8:27                         ` Michal Hocko
2018-09-07  9:36                           ` Dmitry Vyukov
2018-09-07 10:49                             ` Tetsuo Handa
2018-09-07 11:08                             ` Michal Hocko
2018-09-08 14:00                               ` Dmitry Vyukov
2018-09-10 14:36                                 ` Dmitry Vyukov
2018-09-07 10:20                           ` Tetsuo Handa
2019-03-03 11:33 ` INFO: task hung in ext4_da_get_block_prep syzbot

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