From: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Test that POSIX timers using CLOCK_PROCESS_CPUTIME_ID eventually deliver
a signal to all running threads. This effectively tests that the kernel
doesn't prefer any one thread (or subset of threads) for signal delivery.
Signed-off-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
---
v6:
- Update wording on what the test aims to test.
- Fix formatting per checkpatch.pl.
---
tools/testing/selftests/timers/posix_timers.c | 77 +++++++++++++++++++
1 file changed, 77 insertions(+)
diff --git a/tools/testing/selftests/timers/posix_timers.c b/tools/testing/selftests/timers/posix_timers.c
index 0ba500056e63..8a17c0e8d82b 100644
--- a/tools/testing/selftests/timers/posix_timers.c
+++ b/tools/testing/selftests/timers/posix_timers.c
@@ -188,6 +188,80 @@ static int check_timer_create(int which)
return 0;
}
+int remain;
+__thread int got_signal;
+
+static void *distribution_thread(void *arg)
+{
+ while (__atomic_load_n(&remain, __ATOMIC_RELAXED));
+ return NULL;
+}
+
+static void distribution_handler(int nr)
+{
+ if (!__atomic_exchange_n(&got_signal, 1, __ATOMIC_RELAXED))
+ __atomic_fetch_sub(&remain, 1, __ATOMIC_RELAXED);
+}
+
+/*
+ * Test that all running threads _eventually_ receive CLOCK_PROCESS_CPUTIME_ID
+ * timer signals. This primarily tests that the kernel does not favour any one.
+ */
+static int check_timer_distribution(void)
+{
+ int err, i;
+ timer_t id;
+ const int nthreads = 10;
+ pthread_t threads[nthreads];
+ struct itimerspec val = {
+ .it_value.tv_sec = 0,
+ .it_value.tv_nsec = 1000 * 1000,
+ .it_interval.tv_sec = 0,
+ .it_interval.tv_nsec = 1000 * 1000,
+ };
+
+ printf("Check timer_create() per process signal distribution... ");
+ fflush(stdout);
+
+ remain = nthreads + 1; /* worker threads + this thread */
+ signal(SIGALRM, distribution_handler);
+ err = timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id);
+ if (err < 0) {
+ perror("Can't create timer\n");
+ return -1;
+ }
+ err = timer_settime(id, 0, &val, NULL);
+ if (err < 0) {
+ perror("Can't set timer\n");
+ return -1;
+ }
+
+ for (i = 0; i < nthreads; i++) {
+ if (pthread_create(&threads[i], NULL, distribution_thread, NULL)) {
+ perror("Can't create thread\n");
+ return -1;
+ }
+ }
+
+ /* Wait for all threads to receive the signal. */
+ while (__atomic_load_n(&remain, __ATOMIC_RELAXED));
+
+ for (i = 0; i < nthreads; i++) {
+ if (pthread_join(threads[i], NULL)) {
+ perror("Can't join thread\n");
+ return -1;
+ }
+ }
+
+ if (timer_delete(id)) {
+ perror("Can't delete timer\n");
+ return -1;
+ }
+
+ printf("[OK]\n");
+ return 0;
+}
+
int main(int argc, char **argv)
{
printf("Testing posix timers. False negative may happen on CPU execution \n");
@@ -217,5 +291,8 @@ int main(int argc, char **argv)
if (check_timer_create(CLOCK_PROCESS_CPUTIME_ID) < 0)
return ksft_exit_fail();
+ if (check_timer_distribution() < 0)
+ return ksft_exit_fail();
+
return ksft_exit_pass();
}
--
2.40.0.rc1.284.g88254d51c5-goog
