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From:   Marco Elver <elver@google.com>
Date:   Thu, 16 Apr 2020 11:27:38 +0200
Message-ID: <CANpmjNOSo2WqquKJwePdsA1VXS2V94DQZ=RVY9bULbVwGPx1RA@mail.gmail.com>
Subject: Re: [PATCH] checkpatch: Warn about data_race() without comment
To:     Joe Perches <joe@perches.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        Alexander Potapenko <glider@google.com>,
        Andrey Konovalov <andreyknvl@google.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        LKML <linux-kernel@vger.kernel.org>, apw@canonical.com,
        Will Deacon <will@kernel.org>
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On Wed, 1 Apr 2020 at 17:19, Joe Perches <joe@perches.com> wrote:
>
> On Wed, 2020-04-01 at 12:17 +0200, Marco Elver wrote:
> > Warn about applications of data_race() without a comment, to encourage
> > documenting the reasoning behind why it was deemed safe.
> []
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> []
> > @@ -5833,6 +5833,14 @@ sub process {
> >                       }
> >               }
> >
> > +# check for data_race without a comment.
> > +             if ($line =~ /\bdata_race\s*\(/) {
> > +                     if (!ctx_has_comment($first_line, $linenr)) {
> > +                             WARN("DATA_RACE",
> > +                                  "data_race without comment\n" . $herecurr);
> > +                     }
> > +             }
> > +
> >  # check for smp_read_barrier_depends and read_barrier_depends
> >               if (!$file && $line =~ /\b(smp_|)read_barrier_depends\s*\(/) {
> >                       WARN("READ_BARRIER_DEPENDS",

Do we still want to do this? Which tree can pick this up? Or was there
anything left that we missed?

> Sensible enough but it looks like ctx_has_comment should
> be updated to allow c99 comments too, but that should be
> a separate change from this patch.

AFAIK the C99 comment patch is in -mm now.

> Otherwise, this style emits a message:
>
> WARNING: data_race without comment
> #135: FILE: kernel/rcu/tasks.h:135:
> +       int i = data_race(rtp->gp_state); // Let KCSAN detect update races
>

Thanks,
-- Marco