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
fail_message(char * msg)23 static inline void fail_message(char *msg)
24 {
25 fprintf(stderr, msg, file);
26 exit(1);
27 }
28
main(int argc,char * argv[])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 }
88