Re: [PATCH RFC 2/2] checkpatch: warn on usage of VM_BUG_ON() and friends

Joe Perches
2022-08-24T16:52:19Z

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*\(/

> 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);