diff options
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/cgroups/cgroup_event_listener.c | 110 |
1 files changed, 110 insertions, 0 deletions
diff --git a/Documentation/cgroups/cgroup_event_listener.c b/Documentation/cgroups/cgroup_event_listener.c new file mode 100644 index 000000000000..8c2bfc4a6358 --- /dev/null +++ b/Documentation/cgroups/cgroup_event_listener.c | |||
@@ -0,0 +1,110 @@ | |||
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 <errno.h> | ||
9 | #include <fcntl.h> | ||
10 | #include <libgen.h> | ||
11 | #include <limits.h> | ||
12 | #include <stdio.h> | ||
13 | #include <string.h> | ||
14 | #include <unistd.h> | ||
15 | |||
16 | #include <sys/eventfd.h> | ||
17 | |||
18 | #define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>\n" | ||
19 | |||
20 | int main(int argc, char **argv) | ||
21 | { | ||
22 | int efd = -1; | ||
23 | int cfd = -1; | ||
24 | int event_control = -1; | ||
25 | char event_control_path[PATH_MAX]; | ||
26 | char line[LINE_MAX]; | ||
27 | int ret; | ||
28 | |||
29 | if (argc != 3) { | ||
30 | fputs(USAGE_STR, stderr); | ||
31 | return 1; | ||
32 | } | ||
33 | |||
34 | cfd = open(argv[1], O_RDONLY); | ||
35 | if (cfd == -1) { | ||
36 | fprintf(stderr, "Cannot open %s: %s\n", argv[1], | ||
37 | strerror(errno)); | ||
38 | goto out; | ||
39 | } | ||
40 | |||
41 | ret = snprintf(event_control_path, PATH_MAX, "%s/cgroup.event_control", | ||
42 | dirname(argv[1])); | ||
43 | if (ret >= PATH_MAX) { | ||
44 | fputs("Path to cgroup.event_control is too long\n", stderr); | ||
45 | goto out; | ||
46 | } | ||
47 | |||
48 | event_control = open(event_control_path, O_WRONLY); | ||
49 | if (event_control == -1) { | ||
50 | fprintf(stderr, "Cannot open %s: %s\n", event_control_path, | ||
51 | strerror(errno)); | ||
52 | goto out; | ||
53 | } | ||
54 | |||
55 | efd = eventfd(0, 0); | ||
56 | if (efd == -1) { | ||
57 | perror("eventfd() failed"); | ||
58 | goto out; | ||
59 | } | ||
60 | |||
61 | ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]); | ||
62 | if (ret >= LINE_MAX) { | ||
63 | fputs("Arguments string is too long\n", stderr); | ||
64 | goto out; | ||
65 | } | ||
66 | |||
67 | ret = write(event_control, line, strlen(line) + 1); | ||
68 | if (ret == -1) { | ||
69 | perror("Cannot write to cgroup.event_control"); | ||
70 | goto out; | ||
71 | } | ||
72 | |||
73 | while (1) { | ||
74 | uint64_t result; | ||
75 | |||
76 | ret = read(efd, &result, sizeof(result)); | ||
77 | if (ret == -1) { | ||
78 | if (errno == EINTR) | ||
79 | continue; | ||
80 | perror("Cannot read from eventfd"); | ||
81 | break; | ||
82 | } | ||
83 | assert(ret == sizeof(result)); | ||
84 | |||
85 | ret = access(event_control_path, W_OK); | ||
86 | if ((ret == -1) && (errno == ENOENT)) { | ||
87 | puts("The cgroup seems to have removed."); | ||
88 | ret = 0; | ||
89 | break; | ||
90 | } | ||
91 | |||
92 | if (ret == -1) { | ||
93 | perror("cgroup.event_control " | ||
94 | "is not accessable any more"); | ||
95 | break; | ||
96 | } | ||
97 | |||
98 | printf("%s %s: crossed\n", argv[1], argv[2]); | ||
99 | } | ||
100 | |||
101 | out: | ||
102 | if (efd >= 0) | ||
103 | close(efd); | ||
104 | if (event_control >= 0) | ||
105 | close(event_control); | ||
106 | if (cfd >= 0) | ||
107 | close(cfd); | ||
108 | |||
109 | return (ret != 0); | ||
110 | } | ||