linux-kernel - Re: [PATCH] selftests/bpf: use !E instead of comparing with NULL

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Message-ID: <CAADnVQJJ03L5H11P0NYNC9kYy=YkQdWrbpytB2Jps8AuxgamFA@mail.gmail.com>
Date:   Tue, 13 Apr 2021 09:13:24 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     "Bird, Tim" <Tim.Bird@...y.com>
Cc:     Yang Li <yang.lee@...ux.alibaba.com>,
        Shuah Khan <shuah@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] selftests/bpf: use !E instead of comparing with NULL

On Tue, Apr 13, 2021 at 9:10 AM <Tim.Bird@...y.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Alexei Starovoitov <alexei.starovoitov@...il.com>
> >
> > On Tue, Apr 13, 2021 at 2:52 AM Yang Li <yang.lee@...ux.alibaba.com> wrote:
> > >
> > > Fix the following coccicheck warnings:
> > > ./tools/testing/selftests/bpf/progs/profiler.inc.h:189:7-11: WARNING
> > > comparing pointer to 0, suggest !E
> > > ./tools/testing/selftests/bpf/progs/profiler.inc.h:361:7-11: WARNING
> > > comparing pointer to 0, suggest !E
> > > ./tools/testing/selftests/bpf/progs/profiler.inc.h:386:14-18: WARNING
> > > comparing pointer to 0, suggest !E
> > > ./tools/testing/selftests/bpf/progs/profiler.inc.h:402:14-18: WARNING
> > > comparing pointer to 0, suggest !E
> > > ./tools/testing/selftests/bpf/progs/profiler.inc.h:433:7-11: WARNING
> > > comparing pointer to 0, suggest !E
> > > ./tools/testing/selftests/bpf/progs/profiler.inc.h:534:14-18: WARNING
> > > comparing pointer to 0, suggest !E
> > > ./tools/testing/selftests/bpf/progs/profiler.inc.h:625:7-11: WARNING
> > > comparing pointer to 0, suggest !E
> > > ./tools/testing/selftests/bpf/progs/profiler.inc.h:767:7-11: WARNING
> > > comparing pointer to 0, suggest !E
> > >
> > > Reported-by: Abaci Robot <abaci@...ux.alibaba.com>
> > > Signed-off-by: Yang Li <yang.lee@...ux.alibaba.com>
> > > ---
> > >  tools/testing/selftests/bpf/progs/profiler.inc.h | 22 +++++++++++-----------
> > >  1 file changed, 11 insertions(+), 11 deletions(-)
> > >
> > > diff --git a/tools/testing/selftests/bpf/progs/profiler.inc.h b/tools/testing/selftests/bpf/progs/profiler.inc.h
> > > index 4896fdf8..a33066c 100644
> > > --- a/tools/testing/selftests/bpf/progs/profiler.inc.h
> > > +++ b/tools/testing/selftests/bpf/progs/profiler.inc.h
> > > @@ -189,7 +189,7 @@ static INLINE void populate_ancestors(struct task_struct* task,
> > >  #endif
> > >         for (num_ancestors = 0; num_ancestors < MAX_ANCESTORS; num_ancestors++) {
> > >                 parent = BPF_CORE_READ(parent, real_parent);
> > > -               if (parent == NULL)
> > > +               if (!parent)
> >
> > Sorry, but I'd like the progs to stay as close as possible to the way
> > they were written.
> Why?
>
> > They might not adhere to kernel coding style in some cases.
> > The code could be grossly inefficient and even buggy.
> There would have to be a really good reason to accept
> grossly inefficient and even buggy code into the kernel.
>
> Can you please explain what that reason is?

It's not the kernel. It's a test of bpf program.