From: Mykyta Yatsenko <yatsenko@meta.com>
Date: Thu, 25 Sep 2025 21:52:30 +0000 (+0100)
Subject: selftests/bpf: Fix flaky bpf_cookie selftest
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=105eb5dc74109a9f53c2f26c9a918d9347a73595;p=users%2Fhch%2Fmisc.git

selftests/bpf: Fix flaky bpf_cookie selftest

bpf_cookie can fail on perf_event_open(), when it runs after the task_work
selftest. The task_work test causes perf to lower
sysctl_perf_event_sample_rate, and bpf_cookie uses sample_freq,
which is validated against that sysctl. As a result,
perf_event_open() rejects the attr if the (now tighter) limit is
exceeded.

>From perf_event_open():
if (attr.freq) {
	if (attr.sample_freq > sysctl_perf_event_sample_rate)
		return -EINVAL;
} else {
	if (attr.sample_period & (1ULL << 63))
		return -EINVAL;
}

Switch bpf_cookie to use sample_period, which is not checked against
sysctl_perf_event_sample_rate.

Signed-off-by: Mykyta Yatsenko <yatsenko@meta.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20250925215230.265501-1-mykyta.yatsenko5@gmail.com
---

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
index 4a0670c056ba..75f4dff7d042 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
@@ -450,8 +450,7 @@ static void pe_subtest(struct test_bpf_cookie *skel)
 	attr.size = sizeof(attr);
 	attr.type = PERF_TYPE_SOFTWARE;
 	attr.config = PERF_COUNT_SW_CPU_CLOCK;
-	attr.freq = 1;
-	attr.sample_freq = 10000;
+	attr.sample_period = 100000;
 	pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
 	if (!ASSERT_GE(pfd, 0, "perf_fd"))
 		goto cleanup;