RE: [PATCH] selftests/bpf: use !E instead of comparing with NULL

From: <Tim.Bird@sony.com>
To: <alexei.starovoitov@gmail.com>, <yang.lee@linux.alibaba.com>
Cc: <shuah@kernel.org>, <ast@kernel.org>, <daniel@iogearbox.net>,
	<andrii@kernel.org>, <kafai@fb.com>, <songliubraving@fb.com>,
	<yhs@fb.com>, <john.fastabend@gmail.com>, <kpsingh@kernel.org>,
	<linux-kselftest@vger.kernel.org>, <netdev@vger.kernel.org>,
	<bpf@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] selftests/bpf: use !E instead of comparing with NULL
Date: Tue, 13 Apr 2021 16:10:27 +0000	[thread overview]
Message-ID: <BN7PR13MB24996213858443821CA7E400FD4F9@BN7PR13MB2499.namprd13.prod.outlook.com> (raw)
In-Reply-To: <CAADnVQJmsipci_ou6OOFGC6O9z935jFw4+pe7YQvvh2=eCoarQ@mail.gmail.com>

> -----Original Message-----
> From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
> 
> On Tue, Apr 13, 2021 at 2:52 AM Yang Li <yang.lee@linux.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@linux.alibaba.com>
> > Signed-off-by: Yang Li <yang.lee@linux.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?

> Please don't run spell checks, coccicheck, checkpatch.pl on them.

 -- Tim