Signed-off-by: Preetpalbugs preetpal.singh@s.amity.edu --- posix_timers.c | 290 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 290 insertions(+) create mode 100644 posix_timers.c
diff --git a/posix_timers.c b/posix_timers.c new file mode 100644 index 0000000..486b71b --- /dev/null +++ b/posix_timers.c @@ -0,0 +1,290 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2013 Red Hat, Inc., Frederic Weisbecker fweisbec@redhat.com + * + * Selftests for a few posix timers interface. + * + * Kernel loop code stolen from Steven Rostedt srostedt@redhat.com + */ + +#include <sys/time.h> +#include <stdio.h> +#include <signal.h> +#include <unistd.h> +#include <time.h> +#include <pthread.h> + +#include "../kselftest.h" + +#define DELAY 2 +#define USECS_PER_SEC 1000000 + +static volatile int done; + +/* Busy loop in userspace to elapse ITIMER_VIRTUAL */ +static void user_loop(void) +{ + while (!done); +} + +/* + * Try to spend as much time as possible in kernelspace + * to elapse ITIMER_PROF. + */ +static void kernel_loop(void) +{ + void *addr = sbrk(0); + int err = 0; + + while (!done && !err) { + err = brk(addr + 4096); + err |= brk(addr); + } +} + +/* + * Sleep until ITIMER_REAL expiration. + */ +static void idle_loop(void) +{ + pause(); +} + +static void sig_handler(int nr) +{ + done = 1; +} + +/* + * Check the expected timer expiration matches the GTOD elapsed delta since + * we armed the timer. Keep a 0.5 sec error margin due to various jitter. + */ +static int check_diff(struct timeval start, struct timeval end) +{ + long long diff; + + diff = end.tv_usec - start.tv_usec; + diff += (end.tv_sec - start.tv_sec) * USECS_PER_SEC; + + if (llabs(diff - DELAY * USECS_PER_SEC) > USECS_PER_SEC / 2) { + printf("Diff too high: %lld..", diff); + return -1; + } + + return 0; +} + +static int check_itimer(int which) +{ + const char *name; + int err; + struct timeval start, end; + struct itimerval val = { + .it_value.tv_sec = DELAY, + }; + + if (which == ITIMER_VIRTUAL) + name = "ITIMER_VIRTUAL"; + else if (which == ITIMER_PROF) + name = "ITIMER_PROF"; + else if (which == ITIMER_REAL) + name = "ITIMER_REAL"; + else + return -1; + + done = 0; + + if (which == ITIMER_VIRTUAL) + signal(SIGVTALRM, sig_handler); + else if (which == ITIMER_PROF) + signal(SIGPROF, sig_handler); + else if (which == ITIMER_REAL) + signal(SIGALRM, sig_handler); + + err = gettimeofday(&start, NULL); + if (err < 0) { + ksft_perror("Can't call gettimeofday()"); + return -1; + } + + err = setitimer(which, &val, NULL); + if (err < 0) { + ksft_perror("Can't set timer"); + return -1; + } + + if (which == ITIMER_VIRTUAL) + user_loop(); + else if (which == ITIMER_PROF) + kernel_loop(); + else if (which == ITIMER_REAL) + idle_loop(); + + err = gettimeofday(&end, NULL); + if (err < 0) { + ksft_perror("Can't call gettimeofday()"); + return -1; + } + + ksft_test_result(check_diff(start, end) == 0, "%s\n", name); + + return 0; +} + +static int check_timer_create(int which) +{ + const char *type; + int err; + timer_t id; + struct timeval start, end; + struct itimerspec val = { + .it_value.tv_sec = DELAY, + }; + + if (which == CLOCK_THREAD_CPUTIME_ID) { + type = "thread"; + } else if (which == CLOCK_PROCESS_CPUTIME_ID) { + type = "process"; + } else { + ksft_print_msg("Unknown timer_create() type %d\n", which); + return -1; + } + + done = 0; + err = timer_create(which, NULL, &id); + if (err < 0) { + ksft_perror("Can't create timer"); + return -1; + } + signal(SIGALRM, sig_handler); + + err = gettimeofday(&start, NULL); + if (err < 0) { + ksft_perror("Can't call gettimeofday()"); + return -1; + } + + err = timer_settime(id, 0, &val, NULL); + if (err < 0) { + ksft_perror("Can't set timer"); + return -1; + } + + user_loop(); + + err = gettimeofday(&end, NULL); + if (err < 0) { + ksft_perror("Can't call gettimeofday()"); + return -1; + } + + ksft_test_result(check_diff(start, end) == 0, + "timer_create() per %s\n", type); + + return 0; +} + +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\n"; + if (timer_settime(id, 0, &val, NULL)) + return "Can't set timer\n"; + + while (ctd_count > 0 && !ctd_failed) + ; + + if (timer_delete(id)) + return "Can't delete timer\n"; + + 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\n"; + if (pthread_create(&ctd_thread, NULL, ctd_thread_func, NULL)) + goto err; + + errmsg = "Cannot join thread\n"; + if (pthread_join(ctd_thread, (void **)&errmsg) || errmsg) + goto err; + + if (!ctd_failed) + ksft_test_result_pass("check signal distribution\n"); + else if (ksft_min_kernel_version(6, 3)) + ksft_test_result_fail("check signal distribution\n"); + else + ksft_test_result_skip("check signal distribution (old kernel)\n"); + return 0; +err: + ksft_print_msg("%s", errmsg); + return -1; +} + +int main(int argc, char **argv) +{ + ksft_print_header(); + ksft_set_plan(6); + + ksft_print_msg("Testing POSIX timers. False negative may happen on CPU execution \n"); + ksft_print_msg("This may happen on CPU-based timers if other threads run on the CPU...\n"); + + if (check_itimer(ITIMER_VIRTUAL) < 0) + ksft_exit_fail(); + + if (check_itimer(ITIMER_PROF) < 0) + ksft_exit_fail(); + + if (check_itimer(ITIMER_REAL) < 0) + ksft_exit_fail(); + + if (check_timer_create(CLOCK_THREAD_CPUTIME_ID) < 0) + ksft_exit_fail(); + + /* + * It's unfortunately hard to reliably test a timer expiration + * on parallel multithread cputime. We could arm it to expire + * on DELAY * nr_threads, with nr_threads busy looping, then wait + * the normal DELAY since the time is elapsing nr_threads faster. + * But for that we need to ensure we have real physical free CPUs + * to ensure true parallelism. So test only one thread until we + * find a better solution. + */ + if (check_timer_create(CLOCK_PROCESS_CPUTIME_ID) < 0) + ksft_exit_fail(); + + if (check_timer_distribution() < 0) + ksft_exit_fail(); + + ksft_finished(); +}