+ checkpatch-warn-on-usage-of-vm_bug_on-and-other-bug-variants.patch added to mm-nonmm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: checkpatch: warn on usage of VM_BUG_ON() and other BUG variants
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     checkpatch-warn-on-usage-of-vm_bug_on-and-other-bug-variants.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/checkpatch-warn-on-usage-of-vm_bug_on-and-other-bug-variants.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***

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------------------------------------------------------
From: David Hildenbrand <david@redhat.com>
Subject: checkpatch: warn on usage of VM_BUG_ON() and other BUG variants
Date: Tue, 20 Sep 2022 14:23:02 +0200

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 other BUG variants as well.  While at it,
make it clearer that the kernel really shouldn't be crashed.

As there are some subsystem BUG macros that actually don't end up crashing
the kernel -- for example, KVM_BUG_ON() -- exclude these manually.

[1] https://lore.kernel.org/r/CAHk-=wg40EAZofO16Eviaj7mfqDhZ2gVEbvfsMf6gYzspRjYvw@mail.gmail.com

Link: https://lkml.kernel.org/r/20220920122302.99195-4-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dave Young <dyoung@redhat.com>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Dwaipayan Ray <dwaipayanray1@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joe Perches <joe@perches.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/scripts/checkpatch.pl~checkpatch-warn-on-usage-of-vm_bug_on-and-other-bug-variants
+++ a/scripts/checkpatch.pl
@@ -4745,12 +4745,12 @@ sub process {
 			}
 		}
 
-# avoid BUG() or BUG_ON()
-		if ($line =~ /\b(?:BUG|BUG_ON)\b/) {
+# do not use BUG() or variants
+		if ($line =~ /\b(?!AA_|BUILD_|DCCP_|IDA_|KVM_|RWLOCK_|snd_|SPIN_)(?:[a-zA-Z_]*_)?BUG(?:_ON)?(?:_[A-Z_]+)?\s*\(/) {
 			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);
+				      "Do not crash the kernel unless it is unavoidable - use WARN_ON_ONCE & recovery code (if reasonable) rather than BUG() or variants.\n" . $herecurr);
 		}
 
 # avoid LINUX_VERSION_CODE
_

Patches currently in -mm which might be from david@redhat.com are

mm-gup-replace-foll_numa-by-gup_can_follow_protnone.patch
mm-gup-use-gup_can_follow_protnone-also-in-gup-fast.patch
mm-fixup-documentation-regarding-pte_numa-and-prot_numa.patch
coding-stylerst-document-bug-and-warn-rules-do-not-crash-the-kernel.patch
checkpatch-warn-on-usage-of-vm_bug_on-and-other-bug-variants.patch