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git.proxmox.com Git - mirror_ubuntu-bionic-kernel.git/blob - tools/cgroup/cgroup_event_listener.c
1 // SPDX-License-Identifier: GPL-2.0
3 * cgroup_event_listener.c - Simple listener of cgroup events
5 * Copyright (C) Kirill A. Shutemov <kirill@shutemov.name>
18 #include <sys/eventfd.h>
20 #define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>"
22 int main(int argc
, char **argv
)
26 int event_control
= -1;
27 char event_control_path
[PATH_MAX
];
32 errx(1, "%s", USAGE_STR
);
34 cfd
= open(argv
[1], O_RDONLY
);
36 err(1, "Cannot open %s", argv
[1]);
38 ret
= snprintf(event_control_path
, PATH_MAX
, "%s/cgroup.event_control",
41 errx(1, "Path to cgroup.event_control is too long");
43 event_control
= open(event_control_path
, O_WRONLY
);
44 if (event_control
== -1)
45 err(1, "Cannot open %s", event_control_path
);
49 err(1, "eventfd() failed");
51 ret
= snprintf(line
, LINE_MAX
, "%d %d %s", efd
, cfd
, argv
[2]);
53 errx(1, "Arguments string is too long");
55 ret
= write(event_control
, line
, strlen(line
) + 1);
57 err(1, "Cannot write to cgroup.event_control");
62 ret
= read(efd
, &result
, sizeof(result
));
66 err(1, "Cannot read from eventfd");
68 assert(ret
== sizeof(result
));
70 ret
= access(event_control_path
, W_OK
);
71 if ((ret
== -1) && (errno
== ENOENT
)) {
72 puts("The cgroup seems to have removed.");
77 err(1, "cgroup.event_control is not accessible any more");
79 printf("%s %s: crossed\n", argv
[1], argv
[2]);