linux-kernel - Re: [PATCH perf/core 15/22] selftests/bpf: Add hit/attach/detach race optimized uprobe test

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aAozzY6ls7LLXNSc@krava>
Date: Thu, 24 Apr 2025 14:51:25 +0200
From: Jiri Olsa <olsajiri@...il.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
	Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
	x86@...nel.org, Song Liu <songliubraving@...com>,
	Yonghong Song <yhs@...com>,
	John Fastabend <john.fastabend@...il.com>,
	Hao Luo <haoluo@...gle.com>, Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Alan Maguire <alan.maguire@...cle.com>,
	David Laight <David.Laight@...lab.com>,
	Thomas Weißschuh <thomas@...ch.de>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH perf/core 15/22] selftests/bpf: Add hit/attach/detach
 race optimized uprobe test

On Wed, Apr 23, 2025 at 10:42:43AM -0700, Andrii Nakryiko wrote:

SNIP

> > +
> > +static void test_uprobe_race(void)
> > +{
> > +       int err, i, nr_threads;
> > +       pthread_t *threads;
> > +
> > +       nr_threads = libbpf_num_possible_cpus();
> > +       if (!ASSERT_GE(nr_threads, 0, "libbpf_num_possible_cpus"))
> 
> I hope there are strictly more than zero CPUs... ;)
> 
> > +               return;
> > +
> > +       threads = malloc(sizeof(*threads) * nr_threads);
> > +       if (!ASSERT_OK_PTR(threads, "malloc"))
> > +               return;
> > +
> > +       for (i = 0; i < nr_threads; i++) {
> > +               err = pthread_create(&threads[i], NULL, i % 2 ? worker_trigger : worker_attach,
> > +                                    NULL);
> 
> What happens when three is just one CPU?
> 

right, we need at least 2 threads, how about the change below

thanks,
jirka


---
diff --git a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
index d55c3579cebe..c885f097eed4 100644
--- a/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
+++ b/tools/testing/selftests/bpf/prog_tests/uprobe_syscall.c
@@ -701,8 +701,9 @@ static void test_uprobe_race(void)
 	pthread_t *threads;
 
 	nr_threads = libbpf_num_possible_cpus();
-	if (!ASSERT_GE(nr_threads, 0, "libbpf_num_possible_cpus"))
+	if (!ASSERT_GT(nr_threads, 0, "libbpf_num_possible_cpus"))
 		return;
+	nr_threads = max(2, nr_threads);
 
 	threads = malloc(sizeof(*threads) * nr_threads);
 	if (!ASSERT_OK_PTR(threads, "malloc"))