From: Joe Perches <joe@perches.com>
To: John Hubbard <jhubbard@nvidia.com>,
David Hildenbrand <david@redhat.com>,
linux-kernel@vger.kernel.org
Cc: Baoquan He <bhe@redhat.com>,
linux-doc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
Dave Young <dyoung@redhat.com>, Jonathan Corbet <corbet@lwn.net>,
Nicholas Piggin <npiggin@gmail.com>,
Jani Nikula <jani.nikula@linux.intel.com>,
linux-mm@kvack.org, David Laight <David.Laight@ACULAB.COM>,
Dwaipayan Ray <dwaipayanray1@gmail.com>,
Andy Whitcroft <apw@canonical.com>,
Lukas Bulwahn <lukas.bulwahn@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@kernel.org>, Vivek Goyal <vgoyal@redhat.com>
Subject: Re: [PATCH v1 3/3] checkpatch: warn on usage of VM_BUG_ON() and other BUG variants
Date: Thu, 22 Sep 2022 19:11:44 -0700 [thread overview]
Message-ID: <3179f4545d3f71358da3e6c6ee18085af601b2eb.camel@perches.com> (raw)
In-Reply-To: <d0c59eb8-baca-26fd-5f10-4a1f89bcf7b9@nvidia.com>
On Thu, 2022-09-22 at 19:05 -0700, John Hubbard wrote:
> On 9/20/22 05:23, 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 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
[]
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> > @@ -4695,12 +4695,12 @@ sub process {
> > }
> > }
> >
> > -# avoid BUG() or BUG_ON()
> > - if ($line =~ /\b(?:BUG|BUG_ON)\b/) {
> > +# do not use BUG() or variants
> > + if ($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.
> > 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.
next prev parent reply other threads:[~2022-09-23 2:21 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-20 12:22 [PATCH v1 0/3] coding-style.rst: document BUG() and WARN() rules David Hildenbrand
2022-09-20 12:23 ` [PATCH v1 1/3] coding-style.rst: document BUG() and WARN() rules ("do not crash the kernel") David Hildenbrand
2022-09-21 4:40 ` Kalle Valo
2022-09-22 14:12 ` David Hildenbrand
2022-09-26 7:44 ` Kalle Valo
2022-10-04 12:32 ` David Hildenbrand
2022-09-22 13:43 ` Akira Yokosawa
2022-09-22 14:41 ` David Hildenbrand
2022-09-23 2:26 ` John Hubbard
2022-09-23 2:37 ` John Hubbard
2022-09-23 10:55 ` David Hildenbrand
2022-09-20 12:23 ` [PATCH v1 2/3] powerpc/prom_init: drop PROM_BUG() David Hildenbrand
2022-09-21 13:02 ` Michael Ellerman
2022-09-21 13:03 ` David Hildenbrand
2022-09-20 12:23 ` [PATCH v1 3/3] checkpatch: warn on usage of VM_BUG_ON() and other BUG variants David Hildenbrand
2022-09-23 2:05 ` John Hubbard
2022-09-23 2:11 ` Joe Perches [this message]
2022-09-23 2:20 ` John Hubbard
2022-09-23 10:58 ` David Hildenbrand
2022-10-04 13:24 ` (subset) [PATCH v1 0/3] coding-style.rst: document BUG() and WARN() rules Michael Ellerman
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