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

David Hildenbrand
2022-08-25T09:58:58Z

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
>

Trying to find more possible variants and exceptions

$ git grep -h -o -E "\b[a-zA-Z]+_BUG(_ON(_[a-zA-Z]+)*)?\(" | sort | uniq
AA_BUG(
-> Ok, no BUG()
ASM_BUG(
-> Bad
BUILD_BUG(
BUILD_BUG_ON(
BUILD_BUG_ON_INVALID(
BUILD_BUG_ON_MSG(
BUILD_BUG_ON_ZERO(
-> Ok
CI_BUG_ON(
-> Bad with CONFIG_DRM_I915_DEBUG
DCCP_BUG(
DCCP_BUG_ON(
-> Ok, no BUG()
do_BUG(
-> BUG implementation, ok.
GEM_BUG_ON(
-> Bad with CONFIG_DRM_I915_DEBUG_GEM_ONCE
GLOCK_BUG_ON(
-> Bad
handle_BUG(
-> BUG implementation, ok.
IDA_BUG_ON(
KVM_BUG(
KVM_BUG_ON(
-> Ok, no BUG()
lkdtm_BUG(
paravirt_BUG(
-> bad
PROM_BUG(
-> unused, will remove
RWLOCK_BUG_ON(
-> Ok, no BUG()
snd_BUG(
snd_BUG_ON(
-> Ok, no BUG()
SNIC_BUG_ON(
-> Bad
SPIN_BUG_ON(
-> Ok, no BUG()
UNWINDER_BUG(
UNWINDER_BUG_ON(
VIRTUAL_BUG_ON(
VM_BUG_ON(
VM_BUG_ON_FOLIO(
VM_BUG_ON_MM(
VM_BUG_ON_PAGE(
VM_BUG_ON_PGFLAGS(
VM_BUG_ON_VMA(
XA_BUG_ON(
-> Bad

So an extended versions of your proposal like (ignoring do_BUG and handle_BUG, people are smart enough to figure that out)

if ($line =~ /\b(?!AA_|BUILD_|DCCP_|IDA_|KVM_|RWLOCK_|snd_|SPIN_)(?:[a-zA-Z_]*_)?BUG(?:_ON)?(?:_[A-Z_]+)?\s*\(/

?

--
Thanks,

David / dhildenb