MIPS: SEAD3: Nuke PIC32 I2C driver.
[sfrench/cifs-2.6.git] / tools / cgroup / cgroup_event_listener.c
1 /*
2  * cgroup_event_listener.c - Simple listener of cgroup events
3  *
4  * Copyright (C) Kirill A. Shutemov <kirill@shutemov.name>
5  */
6
7 #include <assert.h>
8 #include <err.h>
9 #include <errno.h>
10 #include <fcntl.h>
11 #include <libgen.h>
12 #include <limits.h>
13 #include <stdio.h>
14 #include <string.h>
15 #include <unistd.h>
16
17 #include <sys/eventfd.h>
18
19 #define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>"
20
21 int main(int argc, char **argv)
22 {
23         int efd = -1;
24         int cfd = -1;
25         int event_control = -1;
26         char event_control_path[PATH_MAX];
27         char line[LINE_MAX];
28         int ret;
29
30         if (argc != 3)
31                 errx(1, "%s", USAGE_STR);
32
33         cfd = open(argv[1], O_RDONLY);
34         if (cfd == -1)
35                 err(1, "Cannot open %s", argv[1]);
36
37         ret = snprintf(event_control_path, PATH_MAX, "%s/cgroup.event_control",
38                         dirname(argv[1]));
39         if (ret >= PATH_MAX)
40                 errx(1, "Path to cgroup.event_control is too long");
41
42         event_control = open(event_control_path, O_WRONLY);
43         if (event_control == -1)
44                 err(1, "Cannot open %s", event_control_path);
45
46         efd = eventfd(0, 0);
47         if (efd == -1)
48                 err(1, "eventfd() failed");
49
50         ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]);
51         if (ret >= LINE_MAX)
52                 errx(1, "Arguments string is too long");
53
54         ret = write(event_control, line, strlen(line) + 1);
55         if (ret == -1)
56                 err(1, "Cannot write to cgroup.event_control");
57
58         while (1) {
59                 uint64_t result;
60
61                 ret = read(efd, &result, sizeof(result));
62                 if (ret == -1) {
63                         if (errno == EINTR)
64                                 continue;
65                         err(1, "Cannot read from eventfd");
66                 }
67                 assert(ret == sizeof(result));
68
69                 ret = access(event_control_path, W_OK);
70                 if ((ret == -1) && (errno == ENOENT)) {
71                         puts("The cgroup seems to have removed.");
72                         break;
73                 }
74
75                 if (ret == -1)
76                         err(1, "cgroup.event_control is not accessible any more");
77
78                 printf("%s %s: crossed\n", argv[1], argv[2]);
79         }
80
81         return 0;
82 }