#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <time.h>
#include <signal.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <inttypes.h>

// for i in $(seq 50); do provoke > /dev/null & done

static volatile int run = 1;

static void ctrl_c_handler(int sig)
{
    run = 0;
}

static uint64_t milliseconds(void)
{
    struct timespec time;
    if (clock_gettime(CLOCK_MONOTONIC, &time) == 0) {
        return ((uint64_t)time.tv_sec * 1000ULL) + (time.tv_nsec / 1000000);
    }

    fprintf(stderr, "clock_gettime() failed: %s\n", strerror(errno));
    exit(-1);
}

int main(void)
{
    uint32_t i, error_cnt = 0;
    uint64_t prev_time = 0;
    int      tid = syscall(SYS_gettid);

    signal(SIGINT, ctrl_c_handler);

    for (i = 0; i < 10000 && run; i++) {
        uint64_t cur_time = milliseconds();

        if (cur_time < prev_time) {
            error_cnt++;
            fprintf(stderr, "Error: tid = %d: clock_gettime(): Prev = %" PRIu64
	            ", Cur = %" PRIu64 ", diff = -%" PRIu64 "\n",
		    tid, prev_time, cur_time, prev_time - cur_time);
        } else {
            fprintf(stdout, "Info:  tid = %d: clock_gettime(): Prev = %" PRIu64
	            ", Cur = %" PRIu64 ", diff =  %" PRIu64 "\n",
		    tid, prev_time, cur_time, cur_time - prev_time);
        }

        prev_time = cur_time;
    }

    fprintf(stderr, "tid = %d: Ran %u times. error_cnt = %u, success_cnt = %u\n",
            tid, i, error_cnt, i - error_cnt);

    return error_cnt ? -1 : 0;
}