Re: [PATCH] selftests/timers/posix_timers: reimplement check_timer_distribution()

On Sat, 6 Apr 2024 at 17:12, Oleg Nesterov oleg@redhat.com wrote:

Dmitry, Thomas,

To simplify the review I've attached the code with this patch applied below.

Yes, this changes the "semantics" of check_timer_distribution(), perhaps it should be renamed.

But I do not see a better approach, and in fact I think that

    Test that all running threads _eventually_ receive CLOCK_PROCESS_CPUTIME_ID

is the wrong goal.

Do you agree?

Oleg.

static pthread_t ctd_thread; static volatile int ctd_count, ctd_failed;

static void ctd_sighandler(int sig) { if (pthread_self() != ctd_thread) ctd_failed = 1; ctd_count--; }

static void *ctd_thread_func(void *arg) { 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, }; timer_t id;

    /* 1/10 seconds to ensure the leader sleeps */
    usleep(10000);

    ctd_count = 100;
    if (timer_create(CLOCK_PROCESS_CPUTIME_ID, NULL, &id))
            return "Can't create timer";
    if (timer_settime(id, 0, &val, NULL))
            return "Can't set timer";

    while (ctd_count > 0 && !ctd_failed)
            ;

    if (timer_delete(id))
            return "Can't delete timer";

    return NULL;

}

/*

• Test that only the running thread receives the timer signal.

*/ static int check_timer_distribution(void) { const char *errmsg;

    signal(SIGALRM, ctd_sighandler);

    errmsg = "Can't create thread";
    if (pthread_create(&ctd_thread, NULL, ctd_thread_func, NULL))
            goto err;

    errmsg = "Can't join thread";
    if (pthread_join(ctd_thread, (void **)&errmsg) || errmsg)
            goto err;

    if (ctd_failed)
            ksft_test_result_skip("No signal distribution. Assuming old kernel\n");

Shouldn't the test fail here? The goal of a test is to fail when things don't work. I don't see any other ksft_test_result_fail() calls, and it does not look that the test will hang on incorrect distribution.

    else
            ksft_test_result_pass("check signal distribution\n");

    return 0;

err: ksft_print_msg(errmsg); return -1; }