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From: Johannes Weiner <hannes@cmpxchg.org>
To: Michal Hocko <mhocko@kernel.org>
Cc: Dmitry Vyukov <dvyukov@google.com>,
	syzbot <syzbot+bab151e82a4e973fa325@syzkaller.appspotmail.com>,
	cgroups@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
	Linux-MM <linux-mm@kvack.org>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Dmitry Torokhov <dtor@google.com>
Subject: Re: WARNING in try_charge
Date: Mon, 6 Aug 2018 11:31:07 -0400
Message-ID: <20180806153107.GD9888@cmpxchg.org> (raw)
In-Reply-To: <20180806142124.GP19540@dhcp22.suse.cz>

On Mon, Aug 06, 2018 at 04:21:24PM +0200, Michal Hocko wrote:
> On Mon 06-08-18 13:57:38, Dmitry Vyukov wrote:
> > On Mon, Aug 6, 2018 at 1:02 PM, Michal Hocko <mhocko@kernel.org> wrote:
> > > If you have a strong reason to believe that this is an abuse of WARN I
> > > am all happy to change that. But I haven't heard any yet, to be honest.
> > 
> > WARN must not be used for anything that is not kernel bugs. If this is
> > not kernel bug, WARN must not be used here.
> 
> This is rather strong wording without any backing arguments. I strongly
> doubt 90% of existing WARN* match this expectation. WARN* has
> traditionally been a way to tell that something suspicious is going on.
> Those situation are mostly likely not fatal but it is good to know they
> are happening.

I have to agree with Dmitry here. WARN should indicate a real kernel
issue, not user input that knowingly triggers undesirable behavior in
the kernel. It's our assert() for states we don't think are possible.

I would wager that MOST developers and users understand it that way.

  parent reply index

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-04 13:33 syzbot
2018-08-04 13:45 ` Tetsuo Handa
2018-08-05 11:33   ` Tetsuo Handa
2018-08-05  8:14 ` syzbot
2018-08-06  9:15 ` Michal Hocko
2018-08-06  9:30   ` Dmitry Vyukov
2018-08-06  9:48     ` Michal Hocko
2018-08-06 10:34       ` Dmitry Vyukov
2018-08-06 11:02         ` Michal Hocko
2018-08-06 11:57           ` Dmitry Vyukov
2018-08-06 14:21             ` Michal Hocko
2018-08-06 14:58               ` Dmitry Vyukov
2018-08-06 17:30                 ` Michal Hocko
2018-08-06 17:53                   ` Dmitry Vyukov
2018-08-06 15:07               ` Dmitry Vyukov
2018-08-06 15:31               ` Johannes Weiner [this message]
2018-08-06 10:39       ` Dmitry Vyukov
2018-08-06 10:47         ` Tetsuo Handa
2018-08-06 11:09           ` Michal Hocko
2018-08-06 11:27           ` syzbot
2018-08-06 11:32             ` Michal Hocko
2018-08-06 11:58               ` Dmitry Vyukov
2018-08-06 14:41               ` Tetsuo Handa
2018-08-06 14:58                 ` Michal Hocko
2018-08-06 15:12                   ` Tetsuo Handa
2018-08-06 14:54               ` David Howells
2018-08-06 15:04                 ` Tetsuo Handa
2018-08-06 11:00         ` syzbot
2018-08-06 15:32         ` Tetsuo Handa
2018-08-06 15:42           ` syzbot
2018-08-06 16:02             ` Tetsuo Handa
2018-08-06 17:44             ` Michal Hocko
2018-08-06 17:49               ` Dmitry Vyukov
2018-08-06 17:56               ` Michal Hocko
2018-08-06 18:13                 ` Michal Hocko
2018-08-06 18:23                   ` syzbot
2018-08-06 18:55                     ` Michal Hocko
2018-08-06 19:12                       ` syzbot
2018-08-06 19:45                         ` Michal Hocko
2018-08-06 19:46                           ` Michal Hocko
2018-08-07 11:18                       ` Dmitry Vyukov
2018-08-07 11:25                         ` Michal Hocko
2018-08-06 18:39                   ` Michal Hocko
2018-08-06 20:26                 ` Tetsuo Handa
2018-08-06 20:34                   ` Michal Hocko
2018-08-06 20:46                     ` Tetsuo Handa
2018-08-06 20:55                       ` Michal Hocko
2018-08-06 21:50                         ` Tetsuo Handa
2018-08-07 10:19                           ` Tetsuo Handa
2018-08-09 13:57 ` Tetsuo Handa
2018-08-09 15:07   ` Michal Hocko
2018-08-09 21:05     ` Tetsuo Handa
2018-08-09 15:34   ` Johannes Weiner

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