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    SubjectRe: [PATCH v6 2/2] selftests/timers/posix_timers: Test delivery of signals across threads
    Muhammad,

    I am sorry, but... are you aware that this patch was applied over a year ago,
    and then this code was updated to use the ksft_API?

    Oleg.

    On 04/07, Muhammad Usama Anjum wrote:
    >
    > On 3/16/23 5:30 PM, Marco Elver wrote:
    > > From: Dmitry Vyukov <dvyukov@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 <dvyukov@google.com>
    > > Signed-off-by: Marco Elver <elver@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
    >


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