tools/testing/selftests/cgroup/wait_inotify.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Wait until an inotify event on the given cgroup file.
   4  */
   5 #include <linux/limits.h>
   6 #include <sys/inotify.h>
   7 #include <sys/mman.h>
   8 #include <sys/ptrace.h>
   9 #include <sys/stat.h>
  10 #include <sys/types.h>
  11 #include <errno.h>
  12 #include <fcntl.h>
  13 #include <poll.h>
  14 #include <stdio.h>
  15 #include <stdlib.h>
  16 #include <string.h>
  17 #include <unistd.h>
  18
  19 static const char usage[] = "Usage: %s [-v] <cgroup_file>\n";
  20 static char *file;
  21 static int verbose;
  22
  23 static inline void fail_message(char *msg)
  24 {
  25         fprintf(stderr, msg, file);
  26         exit(1);
  27 }
  28
  29 int main(int argc, char *argv[])
  30 {
  31         char *cmd = argv[0];
  32         int c, fd;
  33         struct pollfd fds = { .events = POLLIN, };
  34
  35         while ((c = getopt(argc, argv, "v")) != -1) {
  36                 switch (c) {
  37                 case 'v':
  38                         verbose++;
  39                         break;
  40                 }
  41                 argv++, argc--;
  42         }
  43
  44         if (argc != 2) {
  45                 fprintf(stderr, usage, cmd);
  46                 return -1;
  47         }
  48         file = argv[1];
  49         fd = open(file, O_RDONLY);
  50         if (fd < 0)
  51                 fail_message("Cgroup file %s not found!\n");
  52         close(fd);
  53
  54         fd = inotify_init();
  55         if (fd < 0)
  56                 fail_message("inotify_init() fails on %s!\n");
  57         if (inotify_add_watch(fd, file, IN_MODIFY) < 0)
  58                 fail_message("inotify_add_watch() fails on %s!\n");
  59         fds.fd = fd;
  60
  61         /*
  62          * poll waiting loop
  63          */
  64         for (;;) {
  65                 int ret = poll(&fds, 1, 10000);
  66
  67                 if (ret < 0) {
  68                         if (errno == EINTR)
  69                                 continue;
  70                         perror("poll");
  71                         exit(1);
  72                 }
  73                 if ((ret > 0) && (fds.revents & POLLIN))
  74                         break;
  75         }
  76         if (verbose) {
  77                 struct inotify_event events[10];
  78                 long len;
  79
  80                 usleep(1000);
  81                 len = read(fd, events, sizeof(events));
  82                 printf("Number of events read = %ld\n",
  83                         len/sizeof(struct inotify_event));
  84         }
  85         close(fd);
  86         return 0;
  87 }