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selftests/timers/posix_timers: Test delivery of signals across threads

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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@google.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230316123028.2890338-2-elver@google.com
This commit is contained in:
Dmitry Vyukov 2023-03-16 13:30:28 +01:00 • committed by Thomas Gleixner
parent bcb7ee7902
commit e797203fb3
1 changed files with 77 additions and 0 deletions
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77
tools/testing/selftests/timers/posix_timers.c
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@ -188,6 +188,80 @@ static int check_timer_create(int which)
return 0; 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) int main(int argc, char **argv)
{ {
printf("Testing posix timers. False negative may happen on CPU execution \n"); 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) if (check_timer_create(CLOCK_PROCESS_CPUTIME_ID) < 0)
return ksft_exit_fail(); return ksft_exit_fail();
if (check_timer_distribution() < 0)
return ksft_exit_fail();
return ksft_exit_pass(); return ksft_exit_pass();
} }