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

David Hildenbrand
2022-08-24T19:00:37Z

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