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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>
This commit is contained in:
Greg Thelen 2013-01-07 11:50:17 -08:00 committed by Tejun Heo
parent 92e015b1cf
commit 799105d514
1 changed files with 22 additions and 50 deletions
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72
tools/cgroup/cgroup_event_listener.c
View File

@ -5,6 +5,7 @@
*/ */
#include <assert.h> #include <assert.h>
#include <err.h>
#include <errno.h> #include <errno.h>
#include <fcntl.h> #include <fcntl.h>
#include <libgen.h> #include <libgen.h>
@ -15,7 +16,7 @@
#include <sys/eventfd.h> #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) int main(int argc, char **argv)
{ {
@ -26,49 +27,33 @@ int main(int argc, char **argv)
char line[LINE_MAX]; char line[LINE_MAX];
int ret; int ret;
if (argc != 3) { if (argc != 3)
fputs(USAGE_STR, stderr); errx(1, "%s", USAGE_STR);
return 1;
}
cfd = open(argv[1], O_RDONLY); cfd = open(argv[1], O_RDONLY);
if (cfd == -1) { if (cfd == -1)
fprintf(stderr, "Cannot open %s: %s\n", argv[1], err(1, "Cannot open %s", argv[1]);
strerror(errno));
goto out;
}
ret = snprintf(event_control_path, PATH_MAX, "%s/cgroup.event_control", ret = snprintf(event_control_path, PATH_MAX, "%s/cgroup.event_control",
dirname(argv[1])); dirname(argv[1]));
if (ret >= PATH_MAX) { if (ret >= PATH_MAX)
fputs("Path to cgroup.event_control is too long\n", stderr); errx(1, "Path to cgroup.event_control is too long");
goto out;
}
event_control = open(event_control_path, O_WRONLY); event_control = open(event_control_path, O_WRONLY);
if (event_control == -1) { if (event_control == -1)
fprintf(stderr, "Cannot open %s: %s\n", event_control_path, err(1, "Cannot open %s", event_control_path);
strerror(errno));
goto out;
}
efd = eventfd(0, 0); efd = eventfd(0, 0);
if (efd == -1) { if (efd == -1)
perror("eventfd() failed"); err(1, "eventfd() failed");
goto out;
}
ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]); ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]);
if (ret >= LINE_MAX) { if (ret >= LINE_MAX)
fputs("Arguments string is too long\n", stderr); errx(1, "Arguments string is too long");
goto out;
}
ret = write(event_control, line, strlen(line) + 1); ret = write(event_control, line, strlen(line) + 1);
if (ret == -1) { if (ret == -1)
perror("Cannot write to cgroup.event_control"); err(1, "Cannot write to cgroup.event_control");
goto out;
}
while (1) { while (1) {
uint64_t result; uint64_t result;
@ -77,34 +62,21 @@ int main(int argc, char **argv)
if (ret == -1) { if (ret == -1) {
if (errno == EINTR) if (errno == EINTR)
continue; continue;
perror("Cannot read from eventfd"); err(1, "Cannot read from eventfd");
break;
} }
assert(ret == sizeof(result)); assert(ret == sizeof(result));
ret = access(event_control_path, W_OK); ret = access(event_control_path, W_OK);
if ((ret == -1) && (errno == ENOENT)) { if ((ret == -1) && (errno == ENOENT)) {
puts("The cgroup seems to have removed."); puts("The cgroup seems to have removed.");
ret = 0;
break;
}
if (ret == -1) {
perror("cgroup.event_control "
"is not accessible any more");
break; break;
} }
if (ret == -1)
err(1, "cgroup.event_control is not accessible any more");
printf("%s %s: crossed\n", argv[1], argv[2]); printf("%s %s: crossed\n", argv[1], argv[2]);
} }
out: return 0;
if (efd >= 0)
close(efd);
if (event_control >= 0)
close(event_control);
if (cfd >= 0)
close(cfd);
return (ret != 0);
} }