perf_link creates a system-wide perf event pinned to CPU 0 (pid=-1, cpu=0) and also pins the test thread to CPU 0. Under concurrent selftests this can lead to cross-test interference and CPU 0 contention, making the test flaky.
Create a per-task perf event instead (pid=0, cpu=-1) and drop CPU pinning from burn_cpu(). Use barrier() to prevent the burn loop from being optimized away. Drop the serial_ prefix so the test can run in parallel. Also remove the stale TODO comment. Tested: ./test_progs -t perf_link -vv ./test_progs -j$(nproc) -t perf_link -vv for i in $(seq 1 50); do ./test_progs -j$(nproc) -t perf_link; done Signed-off-by: Sun Jian <[email protected]> --- .../selftests/bpf/prog_tests/perf_link.c | 20 +++++-------------- 1 file changed, 5 insertions(+), 15 deletions(-) diff --git a/tools/testing/selftests/bpf/prog_tests/perf_link.c b/tools/testing/selftests/bpf/prog_tests/perf_link.c index d940ff87fa08..9e3a0d217af8 100644 --- a/tools/testing/selftests/bpf/prog_tests/perf_link.c +++ b/tools/testing/selftests/bpf/prog_tests/perf_link.c @@ -1,8 +1,7 @@ // SPDX-License-Identifier: GPL-2.0 /* Copyright (c) 2021 Facebook */ #define _GNU_SOURCE -#include <pthread.h> -#include <sched.h> +#include <linux/compiler.h> #include <test_progs.h> #include "testing_helpers.h" #include "test_perf_link.skel.h" @@ -12,23 +11,14 @@ static void burn_cpu(void) { - volatile int j = 0; - cpu_set_t cpu_set; - int i, err; - - /* generate some branches on cpu 0 */ - CPU_ZERO(&cpu_set); - CPU_SET(0, &cpu_set); - err = pthread_setaffinity_np(pthread_self(), sizeof(cpu_set), &cpu_set); - ASSERT_OK(err, "set_thread_affinity"); + int i; /* spin the loop for a while (random high number) */ for (i = 0; i < 1000000; ++i) - ++j; + barrier(); } -/* TODO: often fails in concurrent mode */ -void serial_test_perf_link(void) +void test_perf_link(void) { struct test_perf_link *skel = NULL; struct perf_event_attr attr; @@ -45,7 +35,7 @@ void serial_test_perf_link(void) attr.config = PERF_COUNT_SW_CPU_CLOCK; attr.freq = 1; attr.sample_freq = 1000; - pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC); + pfd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, PERF_FLAG_FD_CLOEXEC); if (!ASSERT_GE(pfd, 0, "perf_fd")) goto cleanup; base-commit: 0b3bb205808195159be633a8cefb602670e856fb -- 2.43.0
