tools/testing/selftests/proc/proc-uptime-001.c

   1 /*
   2  * Copyright © 2018 Alexey Dobriyan <adobriyan@gmail.com>
   3  *
   4  * Permission to use, copy, modify, and distribute this software for any
   5  * purpose with or without fee is hereby granted, provided that the above
   6  * copyright notice and this permission notice appear in all copies.
   7  *
   8  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
   9  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  10  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  11  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  12  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  13  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  14  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  15  */
  16 // Test that boottime value in /proc/uptime and CLOCK_BOOTTIME increment
  17 // monotonically. We don't test idle time monotonicity due to broken iowait
  18 // task counting, cf: comment above get_cpu_idle_time_us()
  19 #undef NDEBUG
  20 #include <assert.h>
  21 #include <stdint.h>
  22 #include <sys/types.h>
  23 #include <sys/stat.h>
  24 #include <fcntl.h>
  25
  26 #include "proc-uptime.h"
  27
  28 int main(void)
  29 {
  30         uint64_t start, u0, u1, c0, c1;
  31         int fd;
  32
  33         fd = open("/proc/uptime", O_RDONLY);
  34         assert(fd >= 0);
  35
  36         u0 = proc_uptime(fd);
  37         start = u0;
  38         c0 = clock_boottime();
  39
  40         do {
  41                 u1 = proc_uptime(fd);
  42                 c1 = clock_boottime();
  43
  44                 /* Is /proc/uptime monotonic ? */
  45                 assert(u1 >= u0);
  46
  47                 /* Is CLOCK_BOOTTIME monotonic ? */
  48                 assert(c1 >= c0);
  49
  50                 /* Is CLOCK_BOOTTIME VS /proc/uptime monotonic ? */
  51                 assert(c0 >= u0);
  52
  53                 u0 = u1;
  54                 c0 = c1;
  55         } while (u1 - start < 100);
  56
  57         return 0;
  58 }