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cgroups: fix cgroup_event_listener error handling

The error handling in cgroup_event_listener.c did not correctly deal
with either an error opening either <control_file> or
cgroup.event_control.  Due to an uninitialized variable the program
exit code was undefined if either of these opens failed.

This patch simplifies and corrects cgroup_event_listener.c error
handling by:
1. using err*() rather than printf(),exit()
2. depending on process exit to close open files

With this patch failures always return non-zero error.

Signed-off-by: Greg Thelen <gthelen@google.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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1 parent 92e015b commit 799105d514384b80cbe3182dbcb4ed30aa07e1f5 Greg Thelen committed with htejun Jan 7, 2013
Showing with 22 additions and 50 deletions.
  1. +22 −50 tools/cgroup/cgroup_event_listener.c
@@ -5,6 +5,7 @@
*/
#include <assert.h>
+#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <libgen.h>
@@ -15,7 +16,7 @@
#include <sys/eventfd.h>
-#define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>\n"
+#define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>"
int main(int argc, char **argv)
{
@@ -26,49 +27,33 @@ int main(int argc, char **argv)
char line[LINE_MAX];
int ret;
- if (argc != 3) {
- fputs(USAGE_STR, stderr);
- return 1;
- }
+ if (argc != 3)
+ errx(1, "%s", USAGE_STR);
cfd = open(argv[1], O_RDONLY);
- if (cfd == -1) {
- fprintf(stderr, "Cannot open %s: %s\n", argv[1],
- strerror(errno));
- goto out;
- }
+ 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) {
- fputs("Path to cgroup.event_control is too long\n", stderr);
- goto out;
- }
+ 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) {
- fprintf(stderr, "Cannot open %s: %s\n", event_control_path,
- strerror(errno));
- goto out;
- }
+ if (event_control == -1)
+ err(1, "Cannot open %s", event_control_path);
efd = eventfd(0, 0);
- if (efd == -1) {
- perror("eventfd() failed");
- goto out;
- }
+ if (efd == -1)
+ err(1, "eventfd() failed");
ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]);
- if (ret >= LINE_MAX) {
- fputs("Arguments string is too long\n", stderr);
- goto out;
- }
+ if (ret >= LINE_MAX)
+ errx(1, "Arguments string is too long");
ret = write(event_control, line, strlen(line) + 1);
- if (ret == -1) {
- perror("Cannot write to cgroup.event_control");
- goto out;
- }
+ if (ret == -1)
+ err(1, "Cannot write to cgroup.event_control");
while (1) {
uint64_t result;
@@ -77,34 +62,21 @@ int main(int argc, char **argv)
if (ret == -1) {
if (errno == EINTR)
continue;
- perror("Cannot read from eventfd");
- break;
+ 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.");
- ret = 0;
- break;
- }
-
- if (ret == -1) {
- perror("cgroup.event_control "
- "is not accessible any more");
+ 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]);
}
-out:
- if (efd >= 0)
- close(efd);
- if (event_control >= 0)
- close(event_control);
- if (cfd >= 0)
- close(cfd);
-
- return (ret != 0);
+ return 0;
}

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