On 3/16/23 5:30 PM, Marco Elver wrote:
> From: Dmitry Vyukov <dvyu...@google.com>
>
> 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 <dvyu...@google.com>
> Signed-off-by: Marco Elver <el...@google.com>
> ---
> 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... ");
Use APIs from kselftest.h. Use ksft_print_msg() here.
> + 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");
ksft_perror() here
> + 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");
ksft_test_result or _pass variant as needed?
> + 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();
> }
--
BR,
Muhammad Usama Anjum
