/*
 * Copyright (C) 2013 Red Hat, Inc., Frederic Weisbecker <fweisbec@redhat.com>
 *
 * Licensed under the terms of the GNU GPL License version 2
 *
 * 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>

#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);

        while (!done) {
                brk(addr + 4096);
                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 (abs(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)
{
        int err;
        struct timeval start, end;
        struct itimerval val = {
                .it_value.tv_sec = DELAY,
        };

        printf("Check itimer ");

        if (which == ITIMER_VIRTUAL)
                printf("virtual... ");
        else if (which == ITIMER_PROF)
                printf("prof... ");
        else if (which == ITIMER_REAL)
                printf("real... ");

        fflush(stdout);

        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) {
                perror("Can't call gettimeofday()\n");
                return -1;
        }

        err = setitimer(which, &val, NULL);
        if (err < 0) {
                perror("Can't set timer\n");
                return -1;
        }

        if (which == ITIMER_VIRTUAL)
                user_loop();
        else if (which == ITIMER_PROF)
                kernel_loop();
        else if (which == ITIMER_REAL)
                idle_loop();

        gettimeofday(&end, NULL);
        if (err < 0) {
                perror("Can't call gettimeofday()\n");
                return -1;
        }

        if (!check_diff(start, end))
                printf("[OK]\n");
        else
                printf("[FAIL]\n");

        return 0;
}

static int check_timer_create(int which)
{
        int err;
        timer_t id;
        struct timeval start, end;
        struct itimerspec val = {
                .it_value.tv_sec = DELAY,
        };

        printf("Check timer_create() ");
        if (which == CLOCK_THREAD_CPUTIME_ID) {
                printf("per thread... ");
        } else if (which == CLOCK_PROCESS_CPUTIME_ID) {
                printf("per process... ");
        }
        fflush(stdout);

        done = 0;
        err = timer_create(which, NULL, &id);
        if (err < 0) {
                perror("Can't create timer\n");
                return -1;
        }
        signal(SIGALRM, sig_handler);

        err = gettimeofday(&start, NULL);
        if (err < 0) {
                perror("Can't call gettimeofday()\n");
                return -1;
        }

        err = timer_settime(id, 0, &val, NULL);
        if (err < 0) {
                perror("Can't set timer\n");
                return -1;
        }

        user_loop();

        gettimeofday(&end, NULL);
        if (err < 0) {
                perror("Can't call gettimeofday()\n");
                return -1;
        }

        if (!check_diff(start, end))
                printf("[OK]\n");
        else
                printf("[FAIL]\n");

        return 0;
}

int main(int argc, char **argv)
{
        int err;

        printf("Testing posix timers. False negative may happen on CPU execution \n");
        printf("based timers if other threads run on the CPU...\n");

        if (check_itimer(ITIMER_VIRTUAL) < 0)
                return -1;

        if (check_itimer(ITIMER_PROF) < 0)
                return -1;

        if (check_itimer(ITIMER_REAL) < 0)
                return -1;

        if (check_timer_create(CLOCK_THREAD_CPUTIME_ID) < 0)
                return -1;

        /*
         * 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)
                return -1;

        return 0;
}