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From:   Lukas Bulwahn <lukas.bulwahn@gmail.com>
Date:   Thu, 6 May 2021 18:02:08 +0200
Message-ID: <CAKXUXMx4dOSb8xub+JtOR8HBrLi_WtGL+L_+3c-rdQQc3XEPLw@mail.gmail.com>
Subject: Re: [PATCH] checkpatch: warn about direct use of send_sig_info and force_sig_info
To:     Dwaipayan Ray <dwaipayanray1@gmail.com>
Cc:     Marco Elver <elver@google.com>,
        "Eric W . Biederman" <ebiederm@xmission.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Andy Whitcroft <apw@canonical.com>,
        Joe Perches <joe@perches.com>
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On Thu, May 6, 2021 at 5:02 PM Dwaipayan Ray <dwaipayanray1@gmail.com> wrote:
>
> On Thu, May 6, 2021 at 6:59 PM Marco Elver <elver@google.com> wrote:
> >
> > Setting up siginfo and using send_sig_info() and force_sig_info()
> > directly is discouraged. Instead, new code wanting to generate signals
> > should use the appropriate helper specific to the signal.
> >
> > Eric mentioned that he'd like to make these static at some point, but
> > until that can happen, let's try to avoid introducing new users of them.
> >
> > Cc: Eric W. Biederman <ebiederm@xmission.com>
> > Signed-off-by: Marco Elver <elver@google.com>
> > ---
> > Eric,
> >
> > While siginfo doesn't need changing often, when it does, it's quite the
> > adventure. We now have the various static asserts. The other thing is
> > usage of {send,force}_sig_info.
> >
> > I think the best option right now is to teach checkpatch.pl about it
> > until they become static.
> >
> > Fyi, I noticed one such new user here:
> > https://lkml.kernel.org/r/20210421024826.13529-1-wangjunqiang@iscas.ac.cn
> >
> > Thanks,
> > -- Marco
> > ---
> >  scripts/checkpatch.pl | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> > index ccb412a74725..3a86aafc3bcd 100755
> > --- a/scripts/checkpatch.pl
> > +++ b/scripts/checkpatch.pl
> > @@ -7153,6 +7153,12 @@ sub process {
> >                              "Where possible, use lockdep_assert_held instead of assertions based on spin_is_locked\n" . $herecurr);
> >                 }
> >
> > +# check for direct use of send_sig_info(), force_sig_info()
> > +               if ($line =~ /\b((force|send)_sig_info)\(/) {
>
> I think this might be a little better as:
> if ($line =~ /\b((?:force|send)_sig_info)\(/) {
>
> Otherwise it's good as it is.
> Tested-by: Dwaipayan Ray <dwaipayanray1@gmail.com>
>

Dwaipayan, do you want to also document this new rule on the
checkpatch documentation?
Marco, maybe you can assist us here with some pointer (lore.kernel.org
link) to the original discussion you had.

Lukas