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Mon, 29 Aug 2022 04:49:26 +0000 Received: from BY5PR12MB4130.namprd12.prod.outlook.com ([fe80::508d:221c:9c9e:e1a5]) by BY5PR12MB4130.namprd12.prod.outlook.com ([fe80::508d:221c:9c9e:e1a5%8]) with mapi id 15.20.5566.021; Mon, 29 Aug 2022 04:49:26 +0000 Message-ID: <29fb251b-4622-4eb6-538d-bab6ac6a76f6@nvidia.com> Date: Sun, 28 Aug 2022 21:49:23 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH RFC 1/2] coding-style.rst: document BUG() and WARN() rules ("do not crash the kernel") Content-Language: en-US To: Linus Torvalds , Dave Young Cc: David Hildenbrand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, kexec@lists.infradead.org, Andrew Morton , Ingo Molnar , David Laight , Jonathan Corbet , Andy Whitcroft , Joe Perches , Dwaipayan Ray , Lukas Bulwahn , Baoquan He , Vivek Goyal , Stephen Johnston , Prarit Bhargava References: <20220824163100.224449-1-david@redhat.com> <20220824163100.224449-2-david@redhat.com> <0db131cf-013e-6f0e-c90b-5c1e840d869c@nvidia.com> From: John Hubbard In-Reply-To: Content-Type: text/plain; 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b=FCo1gCT7sNckewCb+ruZWifSpTt45x4uy2aLSoH3TlIx/1KLpZD2tlIBzwUcEcMU2XICDl Zgw5nEW33Id3BaXlhU+97avI0+MGnt3RWFLsvHRtalZgFKPybRS3kS38hiaWMT2AhgHOro LpzBk1MQ0GcKM05Hds+PacMsY8M7mDc= X-Stat-Signature: k43ckw9s1ae58w3yreujxtkgynpa8ru5 X-Rspamd-Queue-Id: 554DF4001F X-Rspam-User: X-Rspamd-Server: rspam06 Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=Nvidia.com header.s=selector2 header.b="QK/Hv/at"; spf=pass (imf12.hostedemail.com: domain of jhubbard@nvidia.com designates 40.107.212.56 as permitted sender) smtp.mailfrom=jhubbard@nvidia.com; dmarc=pass (policy=reject) header.from=nvidia.com; arc=pass ("microsoft.com:s=arcselector9901:i=1") X-HE-Tag: 1661748574-666057 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 8/28/22 20:07, Linus Torvalds wrote: > On Sun, Aug 28, 2022 at 6:56 PM Dave Young wrote: >> >>> John mentioned PANIC_ON(). >> >> I would vote for PANIC_ON(), it sounds like a good idea, because >> BUG_ON() is not obvious and, PANIC_ON() can alert the code author that >> this will cause a kernel panic and one will be more careful before >> using it. > > People, NO. > > We're trying to get rid of BUG_ON() because it kills the machine. > > Not replace it with another bogus thing that kills a machine. OK, this guidance, and the write-up that follows it, is all very clear, except for one point... > > So no PANIC_ON(). We used to have "panic()" many many years ago, we > got rid of it. We're not re-introducing it. ...here. I count ~1000 calls to panic() in today's kernel, to a function in kernel/panic.c that shows no hint of being removed, nor even deprecated. $ git grep -nw panic\( | wc -l 1321 Could you please clarify that point? (I'm not trying to debate policy, but rather, to figure out what we should write in the documentation of the policy.) thanks, -- John Hubbard NVIDIA