From: Yonghong Song <yhs@fb.com>
Date: Thu, 16 Jan 2020 09:40:04 -0800
Subject: selftests/bpf: Fix test_progs send_signal flakiness with nmi mode
Patch-mainline: v5.6-rc1
Git-commit: 35697c12d7ffd31a56d3c9604066a166b75d0169
References: bsc#1177028
Alexei observed that test_progs send_signal may fail if run
with command line "./test_progs" and the tests will pass
if just run "./test_progs -n 40".
I observed similar issue with nmi subtest failure
and added a delay 100 us in Commit ab8b7f0cb358
("tools/bpf: Add self tests for bpf_send_signal_thread()")
and the problem is gone for me. But the issue still exists
in Alexei's testing environment.
The current code uses sample_freq = 50 (50 events/second), which
may not be enough. But if the sample_freq value is larger than
sysctl kernel/perf_event_max_sample_rate, the perf_event_open
syscall will fail.
This patch changed nmi perf testing to use sample_period = 1,
which means trying to sampling every event. This seems fixing
the issue.
Fixes: ab8b7f0cb358 ("tools/bpf: Add self tests for bpf_send_signal_thread()")
Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200116174004.1522812-1-yhs@fb.com
Acked-by: Gary Lin <glin@suse.com>
---
tools/testing/selftests/bpf/prog_tests/send_signal.c | 6 +-----
1 file changed, 1 insertion(+), 5 deletions(-)
--- a/tools/testing/selftests/bpf/prog_tests/send_signal.c
+++ b/tools/testing/selftests/bpf/prog_tests/send_signal.c
@@ -76,9 +76,6 @@ static void test_send_signal_common(stru
if (CHECK(!skel, "skel_open_and_load", "skeleton open_and_load failed\n"))
goto skel_open_load_failure;
- /* add a delay for child thread to ramp up */
- usleep(100);
-
if (!attr) {
err = test_send_signal_kern__attach(skel);
if (CHECK(err, "skel_attach", "skeleton attach failed\n")) {
@@ -155,8 +152,7 @@ static void test_send_signal_perf(bool s
static void test_send_signal_nmi(bool signal_thread)
{
struct perf_event_attr attr = {
- .sample_freq = 50,
- .freq = 1,
+ .sample_period = 1,
.type = PERF_TYPE_HARDWARE,
.config = PERF_COUNT_HW_CPU_CYCLES,
};