Skip to main content
  • Home
  • Development
  • Documentation
  • Donate
  • Operational login
  • Browse the archive

swh logo
SoftwareHeritage
Software
Heritage
Archive
Features
  • Search

  • Downloads

  • Save code now

  • Add forge now

  • Help

  • 7e636a7
  • /
  • tools
  • /
  • cgroup
  • /
  • cgroup_event_listener.c
Raw File Download
Permalinks

To reference or cite the objects present in the Software Heritage archive, permalinks based on SoftWare Hash IDentifiers (SWHIDs) must be used.
Select below a type of object currently browsed in order to display its associated SWHID and permalink.

  • content
  • directory
content badge Iframe embedding
swh:1:cnt:3d70dc831a7667ca0b267bdf26207749eccac6bd
directory badge Iframe embedding
swh:1:dir:97f9b79b96b9de1ec325e4764640e3e548d79fd6
Citations

This interface enables to generate software citations, provided that the root directory of browsed objects contains a citation.cff or codemeta.json file.
Select below a type of object currently browsed in order to generate citations for them.

  • content
  • directory
Generate software citation in BibTex format (requires biblatex-software package)
Generating citation ...
Generate software citation in BibTex format (requires biblatex-software package)
Generating citation ...
cgroup_event_listener.c
// SPDX-License-Identifier: GPL-2.0
/*
 * cgroup_event_listener.c - Simple listener of cgroup events
 *
 * Copyright (C) Kirill A. Shutemov <kirill@shutemov.name>
 */

#include <assert.h>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <libgen.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <sys/eventfd.h>

#define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>"

int main(int argc, char **argv)
{
	int efd = -1;
	int cfd = -1;
	int event_control = -1;
	char event_control_path[PATH_MAX];
	char line[LINE_MAX];
	int ret;

	if (argc != 3)
		errx(1, "%s", USAGE_STR);

	cfd = open(argv[1], O_RDONLY);
	if (cfd == -1)
		err(1, "Cannot open %s", argv[1]);

	ret = snprintf(event_control_path, PATH_MAX, "%s/cgroup.event_control",
			dirname(argv[1]));
	if (ret >= PATH_MAX)
		errx(1, "Path to cgroup.event_control is too long");

	event_control = open(event_control_path, O_WRONLY);
	if (event_control == -1)
		err(1, "Cannot open %s", event_control_path);

	efd = eventfd(0, 0);
	if (efd == -1)
		err(1, "eventfd() failed");

	ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]);
	if (ret >= LINE_MAX)
		errx(1, "Arguments string is too long");

	ret = write(event_control, line, strlen(line) + 1);
	if (ret == -1)
		err(1, "Cannot write to cgroup.event_control");

	while (1) {
		uint64_t result;

		ret = read(efd, &result, sizeof(result));
		if (ret == -1) {
			if (errno == EINTR)
				continue;
			err(1, "Cannot read from eventfd");
		}
		assert(ret == sizeof(result));

		ret = access(event_control_path, W_OK);
		if ((ret == -1) && (errno == ENOENT)) {
			puts("The cgroup seems to have removed.");
			break;
		}

		if (ret == -1)
			err(1, "cgroup.event_control is not accessible any more");

		printf("%s %s: crossed\n", argv[1], argv[2]);
	}

	return 0;
}

Software Heritage — Copyright (C) 2015–2025, The Software Heritage developers. License: GNU AGPLv3+.
The source code of Software Heritage itself is available on our development forge.
The source code files archived by Software Heritage are available under their own copyright and licenses.
Terms of use: Archive access, API— Contact— JavaScript license information— Web API

back to top