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Wed, 01 Feb 2023 02:03:24 -0800 (PST) Date: Wed, 1 Feb 2023 19:03:20 +0900 From: Hyunmin Lee To: Mike Rapoport Cc: Andrew Morton , Uladzislau Rezki , Christoph Hellwig , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Gwan-gyeong Mun , Jeungwoo Yoo , Sangyun Kim , Hyeonggon Yoo <42.hyeyoo@gmail.com> Subject: Re: [PATCH] replace BUG_ON to WARN_ON Message-ID: <20230201100320.GA5460@min-iamroot> References: <20230127115844.GA1124261@min-iamroot> <20230131105629.GA1195431@min-iamroot> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 2AA4A1A0011 X-Stat-Signature: y8e5fj3bq6it6xfwnk39thpghjmpkaq8 X-HE-Tag: 1675245805-85576 X-HE-Meta: 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 +7F9CzN6 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jan 31, 2023 at 03:47:05PM +0200, Mike Rapoport wrote: > On Tue, Jan 31, 2023 at 07:56:29PM +0900, Hyunmin Lee wrote: > > On Mon, Jan 30, 2023 at 12:14:04PM +0200, Mike Rapoport wrote: > > > Hi, > > > > > > On Fri, Jan 27, 2023 at 08:58:44PM +0900, Hyunmin Lee wrote: > > > > Replace unnacessary BUG_ON to WARN_ON. These BUG_ONs verify aruguments of a function. Thus, the WARN_ONs return an EINVAL error when their condition is true. > > > > > > Some users enable panic_on_warn, so for them WARN_ON will still crash a > > > machine. > > > > > > I think a simple if() will be sufficient. > > > > > Hi Mike, > > > > Thank you for your advice. > > Would you please give feedback about the below opinion? > > - Printing warning messages is helpful to inform what happened in the system to the users. > > - When a simple if() is used instead of WARN_ON, the if() should print a warning message. > > - The condition of the simple if() should also have unlikely() for optimization of system performance. > > - WARN_ON is a macro doing like thoes easily. It has a notifying function and unlikely optimization. > > - Eventhough WARN_ON will still crash like BUG_ON by some users who enable panic_on_warn, it is their intention. They should accept the crash by WARN_ON. > > - Therefore, using WARN_ON looks like natural and efficient. > > As this is a validation of the function parameters, there is no need in > warning messages and if(unlikely()) will do. There is really no point in > WARN_ON() for something that's totally recoverable and very unlikely to > happen. > > > Best, > > Hyunmin > > -- > Sincerely yours, > Mike. Hi Mike, According to your guidance, I will send a v3 patch. Thanks a lot. Best, Min