Kirill A. Shutemov | 1d8fd97 | 2010-03-10 15:22:35 -0800 | [diff] [blame] | 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 " |
Uwe Kleine-König | b595076 | 2010-11-01 15:38:34 -0400 | [diff] [blame] | 94 | "is not accessible any more"); |
Kirill A. Shutemov | 1d8fd97 | 2010-03-10 15:22:35 -0800 | [diff] [blame] | 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 | } |