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

From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: "Bird, Tim" <Tim.Bird@sony.com>
Cc: Yang Li <yang.lee@linux.alibaba.com>,
	Shuah Khan <shuah@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>,
	John Fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@kernel.org>,
	"open list:KERNEL SELFTEST FRAMEWORK" 
	<linux-kselftest@vger.kernel.org>,
	Network Development <netdev@vger.kernel.org>,
	bpf <bpf@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] selftests/bpf: use !E instead of comparing with NULL
Date: Tue, 13 Apr 2021 09:13:24 -0700	[thread overview]
Message-ID: <CAADnVQJJ03L5H11P0NYNC9kYy=YkQdWrbpytB2Jps8AuxgamFA@mail.gmail.com> (raw)
In-Reply-To: <BN7PR13MB24996213858443821CA7E400FD4F9@BN7PR13MB2499.namprd13.prod.outlook.com>

On Tue, Apr 13, 2021 at 9:10 AM <Tim.Bird@sony.com> wrote:
>
>
>
> > -----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?

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