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From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Michal Hocko <mhocko@kernel.org>,
	Johannes Weiner <hannes@cmpxchg.org>,
	linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, guro@fb.com,
	kirill.shutemov@linux.intel.com, linux-kernel@vger.kernel.org,
	rientjes@google.com, yang.s@alibaba-inc.com,
	Andrew Morton <akpm@linux-foundation.org>,
	Petr Mladek <pmladek@suse.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	syzbot <syzbot+77e6b28a7a7106ad0def@syzkaller.appspotmail.com>,
	Calvin Owens <calvinowens@fb.com>
Subject: Re: [PATCH v3] mm: memcontrol: Don't flood OOM messages with no eligible task.
Date: Tue, 23 Oct 2018 09:47:26 +0900	[thread overview]
Message-ID: <20181023004726.GA4612@jagdpanzerIV> (raw)
In-Reply-To: <5d472476-7852-f97b-9412-63536dffaa0e@i-love.sakura.ne.jp>

On (10/19/18 19:35), Tetsuo Handa wrote:
> > 
> > OK, that's a fair point. There was a patch from FB, which would allow us
> > to set a log_level on per-console basis. So the noise goes to heav^W net
> > console; only critical stuff goes to the serial console (if I recall it
> > correctly). I'm not sure what happened to that patch, it was a while ago.
> > I'll try to find that out.
> 
> Per a console loglevel setting would help for several environments.
> But syzbot environment cannot count on netconsole. We can't expect that
> unlimited printk() will become safe.

This target is moving too fast :) RCU stall -> user interaction -> syzbot

I talked to Calvin Owens (who's working on the per-console loglevel
patch set; CC-ed) and Calvin said that "It's in-progress". So we probably
will have this functionality one day. That's all we can do from printk
side wrt user-interaction problem.

> > The problem you are talking about is not MM specific. You can have a
> > faulty SCSI device, corrupted FS, and so and on.
> 
> "a faulty SCSI device, corrupted FS, and so and on" are reporting problems
> which will complete a request. They can use (and are using) ratelimit,
> aren't they?

Looking at scsi_request_fn(), the answer is probably "sure they can;
but no, they aren't". In majority of cases the reason we replace printk
with printk_ratelimit is because someone reports a stall or a lockup.
Otherwise, people use printk(), which is absolutely fine.

	-ss

  reply	other threads:[~2018-10-23  0:47 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-17 10:06 Tetsuo Handa
2018-10-17 10:28 ` Michal Hocko
2018-10-17 11:17   ` Sergey Senozhatsky
2018-10-17 11:29     ` Michal Hocko
2018-10-18  2:46     ` Tetsuo Handa
2018-10-18  2:46       ` Tetsuo Handa
2018-10-18  4:27       ` Sergey Senozhatsky
2018-10-18  5:26         ` Tetsuo Handa
2018-10-18  5:26           ` Tetsuo Handa
2018-10-18  6:10           ` Sergey Senozhatsky
2018-10-18  7:56             ` Michal Hocko
2018-10-18  8:13               ` Sergey Senozhatsky
2018-10-18 11:58                 ` Tetsuo Handa
2018-10-18 23:54                   ` Sergey Senozhatsky
2018-10-19 10:35                     ` Tetsuo Handa
2018-10-19 10:35                       ` Tetsuo Handa
2018-10-23  0:47                       ` Sergey Senozhatsky [this message]
2018-10-23  8:37                       ` Petr Mladek
2018-10-23  8:54                         ` Michal Hocko
2018-10-18 14:30         ` Petr Mladek
2018-10-19  0:18           ` Tetsuo Handa
2018-10-23  8:21             ` Petr Mladek
2018-10-23 10:23               ` Tetsuo Handa
2018-10-18  6:55       ` Michal Hocko
2018-10-18 10:37         ` Tetsuo Handa
2018-10-18 11:23           ` Michal Hocko

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