On Thu, 2022-09-22 at 19:05 -0700, John Hubbard wrote:

On 9/20/22 05:23, David Hildenbrand wrote:

quoted

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 (local)

[]

quoted

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl

[]

quoted

@@ -4695,12 +4695,12 @@ 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*\(/) {

Should this be a separate patch? Adding a bunch of exceptions to the BUG() rules is 
a separate and distinct thing from adding VM_BUG_ON() and other *BUG*() variants to
the mix.

Not in my opinion.

quoted

 			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);

Here's a requested tweak, to clean up the output and fix punctuation:

"Avoid crashing the kernel--use WARN_ON_ONCE() plus recovery code (if feasible) instead of BUG() or variants.\n" . $herecurr);

Fixing punctuation here would be removing the trailing period as checkpatch
only has periods for multi-sentence output messages.

And I think that "Do not crash" is a stronger statement than "Avoid crashing"
so I prefer the original suggestion but it's not a big deal either way.