diff options
Diffstat (limited to 'samples')
| -rw-r--r-- | samples/Kconfig | 6 | ||||
| -rw-r--r-- | samples/Makefile | 1 | ||||
| -rw-r--r-- | samples/cgroup/Makefile | 5 | ||||
| -rw-r--r-- | samples/cgroup/cgroup_event_listener.c | 83 |
4 files changed, 95 insertions, 0 deletions
diff --git a/samples/Kconfig b/samples/Kconfig index b0ddf5f36738..b288d9991d27 100644 --- a/samples/Kconfig +++ b/samples/Kconfig @@ -285,6 +285,12 @@ config SAMPLE_KMEMLEAK Build a sample program which have explicitly leaks memory to test kmemleak +config SAMPLE_CGROUP + bool "Build cgroup sample code" + depends on CGROUPS && CC_CAN_LINK && HEADERS_INSTALL + help + Build samples that demonstrate the usage of the cgroup API. + source "samples/rust/Kconfig" endif # SAMPLES diff --git a/samples/Makefile b/samples/Makefile index 0a551c2b33f4..b85fa64390c5 100644 --- a/samples/Makefile +++ b/samples/Makefile @@ -3,6 +3,7 @@ subdir-$(CONFIG_SAMPLE_AUXDISPLAY) += auxdisplay subdir-$(CONFIG_SAMPLE_ANDROID_BINDERFS) += binderfs +subdir-$(CONFIG_SAMPLE_CGROUP) += cgroup obj-$(CONFIG_SAMPLE_CONFIGFS) += configfs/ obj-$(CONFIG_SAMPLE_CONNECTOR) += connector/ obj-$(CONFIG_SAMPLE_FANOTIFY_ERROR) += fanotify/ diff --git a/samples/cgroup/Makefile b/samples/cgroup/Makefile new file mode 100644 index 000000000000..deef4530f5e7 --- /dev/null +++ b/samples/cgroup/Makefile @@ -0,0 +1,5 @@ +# SPDX-License-Identifier: GPL-2.0 + +userprogs-always-y += cgroup_event_listener + +userccflags += -I usr/include diff --git a/samples/cgroup/cgroup_event_listener.c b/samples/cgroup/cgroup_event_listener.c new file mode 100644 index 000000000000..3d70dc831a76 --- /dev/null +++ b/samples/cgroup/cgroup_event_listener.c @@ -0,0 +1,83 @@ +// 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; +} |