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selftests/bpf: Check for timeout in perf_link test

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Recently perf_link test started unreliably failing on libbpf CI:
  * https://github.com/libbpf/libbpf/actions/runs/11260672407/job/31312405473
  * https://github.com/libbpf/libbpf/actions/runs/11260992334/job/31315514626
  * https://github.com/libbpf/libbpf/actions/runs/11263162459/job/31320458251

Part of the test is running a dummy loop for a while and then checking
for a counter incremented by the test program.

Instead of waiting for an arbitrary number of loop iterations once,
check for the test counter in a loop and use get_time_ns() helper to
enforce a 100ms timeout.

v1: https://lore.kernel.org/bpf/zuRd072x9tumn2iN4wDNs5av0nu5nekMNV4PkR-YwCT10eFFTrUtZBRkLWFbrcCe7guvLStGQlhibo8qWojCO7i2-NGajes5GYIyynexD-w=@pm.me/

Signed-off-by: Ihor Solodrai <ihor.solodrai@pm.me>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20241011153104.249800-1-ihor.solodrai@pm.me
This commit is contained in:
Ihor Solodrai 2024-10-11 15:31:07 +00:00 • committed by Andrii Nakryiko
parent 82370ed5ad
commit e6c209da7e
1 changed files with 13 additions and 2 deletions
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15
tools/testing/selftests/bpf/prog_tests/perf_link.c
View file

@ -4,8 +4,12 @@
#include <pthread.h>
#include <sched.h>
#include <test_progs.h>
#include "testing_helpers.h"
#include "test_perf_link.skel.h"
#define BURN_TIMEOUT_MS 100
#define BURN_TIMEOUT_NS BURN_TIMEOUT_MS * 1000000
static void burn_cpu(void)
{
volatile int j = 0;
@ -32,6 +36,7 @@ void serial_test_perf_link(void)
int run_cnt_before, run_cnt_after;
struct bpf_link_info info;
__u32 info_len = sizeof(info);
__u64 timeout_time_ns;
/* create perf event */
memset(&attr, 0, sizeof(attr));
@ -63,8 +68,14 @@ void serial_test_perf_link(void)
ASSERT_GT(info.prog_id, 0, "link_prog_id");
/* ensure we get at least one perf_event prog execution */
burn_cpu();
ASSERT_GT(skel->bss->run_cnt, 0, "run_cnt");
timeout_time_ns = get_time_ns() + BURN_TIMEOUT_NS;
while (true) {
burn_cpu();
if (skel->bss->run_cnt > 0)
break;
if (!ASSERT_LT(get_time_ns(), timeout_time_ns, "run_cnt_timeout"))
break;
}
/* perf_event is still active, but we close link and BPF program
* shouldn't be executed anymore