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[96.246.38.36]) by smtp.gmail.com with ESMTPSA id q18-v6sm8441882qtg.82.2018.08.06.08.28.07 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 06 Aug 2018 08:28:08 -0700 (PDT) Date: Mon, 6 Aug 2018 11:31:07 -0400 From: Johannes Weiner To: Michal Hocko Cc: Dmitry Vyukov , syzbot , cgroups@vger.kernel.org, LKML , Linux-MM , syzkaller-bugs , Vladimir Davydov , Dmitry Torokhov Subject: Re: WARNING in try_charge Message-ID: <20180806153107.GD9888@cmpxchg.org> References: <0000000000005e979605729c1564@google.com> <20180806091552.GE19540@dhcp22.suse.cz> <20180806094827.GH19540@dhcp22.suse.cz> <20180806110224.GI19540@dhcp22.suse.cz> <20180806142124.GP19540@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180806142124.GP19540@dhcp22.suse.cz> User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 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.