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![Kirill A. Shutemov](/assets/img/avatar_default.png)
An example of cgroup notification API usage. Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Paul Menage <menage@google.com> Cc: Li Zefan <lizf@cn.fujitsu.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: Pavel Emelyanov <xemul@openvz.org> Cc: Dan Malek <dan@embeddedalley.com> Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
110 lines
2.1 KiB
C
110 lines
2.1 KiB
C
/*
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* cgroup_event_listener.c - Simple listener of cgroup events
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*
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* Copyright (C) Kirill A. Shutemov <kirill@shutemov.name>
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*/
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#include <assert.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <libgen.h>
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#include <limits.h>
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/eventfd.h>
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#define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>\n"
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int main(int argc, char **argv)
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{
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int efd = -1;
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int cfd = -1;
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int event_control = -1;
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char event_control_path[PATH_MAX];
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char line[LINE_MAX];
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int ret;
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if (argc != 3) {
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fputs(USAGE_STR, stderr);
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return 1;
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}
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cfd = open(argv[1], O_RDONLY);
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if (cfd == -1) {
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fprintf(stderr, "Cannot open %s: %s\n", argv[1],
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strerror(errno));
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goto out;
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}
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ret = snprintf(event_control_path, PATH_MAX, "%s/cgroup.event_control",
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dirname(argv[1]));
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if (ret >= PATH_MAX) {
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fputs("Path to cgroup.event_control is too long\n", stderr);
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goto out;
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}
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event_control = open(event_control_path, O_WRONLY);
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if (event_control == -1) {
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fprintf(stderr, "Cannot open %s: %s\n", event_control_path,
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strerror(errno));
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goto out;
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}
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efd = eventfd(0, 0);
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if (efd == -1) {
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perror("eventfd() failed");
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goto out;
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}
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ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]);
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if (ret >= LINE_MAX) {
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fputs("Arguments string is too long\n", stderr);
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goto out;
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}
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ret = write(event_control, line, strlen(line) + 1);
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if (ret == -1) {
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perror("Cannot write to cgroup.event_control");
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goto out;
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}
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while (1) {
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uint64_t result;
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ret = read(efd, &result, sizeof(result));
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if (ret == -1) {
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if (errno == EINTR)
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continue;
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perror("Cannot read from eventfd");
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break;
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}
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assert(ret == sizeof(result));
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ret = access(event_control_path, W_OK);
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if ((ret == -1) && (errno == ENOENT)) {
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puts("The cgroup seems to have removed.");
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ret = 0;
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break;
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}
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if (ret == -1) {
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perror("cgroup.event_control "
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"is not accessable any more");
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break;
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}
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printf("%s %s: crossed\n", argv[1], argv[2]);
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}
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out:
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if (efd >= 0)
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close(efd);
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if (event_control >= 0)
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close(event_control);
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if (cfd >= 0)
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close(cfd);
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return (ret != 0);
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}
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