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[2003:cb:c707:c500:5445:cf40:2e32:6e73]) by smtp.gmail.com with ESMTPSA id w5-20020a5d5445000000b0021e571a99d5sm17290174wrv.17.2022.08.24.12.00.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 24 Aug 2022 12:00:13 -0700 (PDT) Message-ID: <693dc564-349b-7174-b096-53d2107f27a8@redhat.com> Date: Wed, 24 Aug 2022 21:00:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.12.0 Subject: Re: [PATCH RFC 2/2] checkpatch: warn on usage of VM_BUG_ON() and friends To: Joe Perches , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, kexec@lists.infradead.org, Linus Torvalds , Andrew Morton , Ingo Molnar , David Laight , Jonathan Corbet , Andy Whitcroft , Dwaipayan Ray , Lukas Bulwahn , Baoquan He , Vivek Goyal , Dave Young References: <20220824163100.224449-1-david@redhat.com> <20220824163100.224449-3-david@redhat.com> <3c250aa26020b2f336fd575a58d06ba26faf1f14.camel@perches.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <3c250aa26020b2f336fd575a58d06ba26faf1f14.camel@perches.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661367617; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=FIiUmby88Yb55/rny3f+ooD+63bbUsdXMXTOH9q/LhQ=; b=4g02Pqpep/chY6en99uxnXaSC+FVa+ToMwMnnI9XTZ+ug9yEhNqNr+9tfj0mXybZwKQg3b +l7frUv9oxJFSA/Ke32CSQ0nTvB1dexG3VH+fLm5gBeaH/7wrlCt0ep7t5RU1AqCQvQ74o qwbtrSnz2h4kZNFkzWk4f+lDf36JZ10= ARC-Authentication-Results: i=1; imf05.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Zh9x3VQK; spf=pass (imf05.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661367617; a=rsa-sha256; cv=none; b=Mc2U6ZviC5bUu8vfUqbUA9lXlBbxQ5eUJY79Q3gXJh/ouDo+e2OaI3f4LLeqSr3M1V3wrz 4QmXYo1isGtjQKaQoH6ek9+GiS+5mo30J25s0EkOe9NeqDKl5csHKUmVSPwnBanm6iE8OL POv0AGPlKxrNKkAIvQn7HfqqASZDG1o= X-Rspam-User: Authentication-Results: imf05.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=Zh9x3VQK; spf=pass (imf05.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 53E0A100041 X-Stat-Signature: 3yriaaq8ndogugnnrj4zhbsutb7e9sfp X-HE-Tag: 1661367617-59228 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 24.08.22 18:52, Joe Perches wrote: > On Wed, 2022-08-24 at 18:31 +0200, David Hildenbrand wrote: >> checkpatch does not point out that VM_BUG_ON() and friends should be >> avoided, however, Linus notes: >> >> VM_BUG_ON() has the exact same semantics as BUG_ON. It is literally >> no different, the only difference is "we can make the code smaller >> because these are less important". [1] >> >> So let's warn on VM_BUG_ON() and friends as well. While at it, make it >> clearer that the kernel really shouldn't be crashed. >> >> Note that there are some other *_BUG_ON flavors, but they are not all >> bad: for example, KVM_BUG_ON() only triggers a WARN_ON_ONCE and then >> flags KVM as being buggy, so we'll not care about them for now here. > [] >> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl > [] >> @@ -4695,12 +4695,12 @@ sub process { >> } >> } >> >> -# avoid BUG() or BUG_ON() >> - if ($line =~ /\b(?:BUG|BUG_ON)\b/) { >> +# do not use BUG(), BUG_ON(), VM_BUG_ON() and friends. >> + if ($line =~ /\b(?:BUG|BUG_ON|VM_BUG_ON|VM_BUG_ON_[A-Z]+)\b/) { > > Perhaps better as something like the below to pick up more variants > > if ($line =~ /\b(?!KVM_|BUILD_)(?:[A-Z_]*_)?BUG(?:_ON)?(?:_[A-Z_]+)?\s*\(/ ... then I'll have to scan the other cases if they do something similar as KVM. ... well, okay, I'll do it. :) > >> my $msg_level = \&WARN; >> $msg_level = \&CHK if ($file); >> &{$msg_level}("AVOID_BUG", >> - "Avoid crashing the kernel - try using WARN_ON & recovery code rather than BUG() or BUG_ON()\n" . $herecurr); > > and maybe: > > "Do not crash the kernel unless it is unavoidable - use WARN_ON_ONCE & recovery code (if reasonable) rather than BUG() or variants\n" . $herecurr); > > Yes, thanks! -- Thanks, David / dhildenb