linux-kernel - Re: [PATCH bpf-next v1 7/8] selftests/bpf: Add selftests for load-acquire and store-release instructions

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Message-ID: <Z6Ffquq8IORjCqrI@google.com>
Date: Tue, 4 Feb 2025 00:30:34 +0000
From: Peilin Ye <yepeilin@...gle.com>
To: Eduard Zingerman <eddyz87@...il.com>
Cc: bpf@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, bpf@...f.org,
	Xu Kuohai <xukuohai@...weicloud.com>,
	David Vernet <void@...ifault.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	John Fastabend <john.fastabend@...il.com>,
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
	Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
	Jonathan Corbet <corbet@....net>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Puranjay Mohan <puranjay@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>, Quentin Monnet <qmo@...nel.org>,
	Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
	Josh Don <joshdon@...gle.com>, Barret Rhoden <brho@...gle.com>,
	Neel Natu <neelnatu@...gle.com>,
	Benjamin Segall <bsegall@...gle.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next v1 7/8] selftests/bpf: Add selftests for
 load-acquire and store-release instructions

Hi Eduard,

One more question (for my understanding):

On Tue, Jan 28, 2025 at 05:06:03PM -0800, Eduard Zingerman wrote:
> On Sat, 2025-01-25 at 02:19 +0000, Peilin Ye wrote:
> > --- a/tools/testing/selftests/bpf/progs/arena_atomics.c
> > +++ b/tools/testing/selftests/bpf/progs/arena_atomics.c
> [...]
> 
> > +SEC("raw_tp/sys_enter")
> > +int load_acquire(const void *ctx)
> > +{
> > +	if (pid != (bpf_get_current_pid_tgid() >> 32))
> > +		return 0;
> 
> Nit: This check is not needed, since bpf_prog_test_run_opts() is used
>      to run the tests.

Could you explain a bit more why it's not needed?

I read commit 0f4feacc9155 ("selftests/bpf: Adding pid filtering for
atomics test") which added those 'pid' checks to atomics/ tests.  The
commit message [1] says the purpose was to "make atomics test able to
run in parallel with other tests", which I couldn't understand.

How using bpf_prog_test_run_opts() makes those 'pid' checks unnecessary?

[1] https://lore.kernel.org/bpf/20211006185619.364369-11-fallentree@fb.com/#r

Thanks,
Peilin Ye