On Tue, Jul 23, 2019 at 10:39:07AM -0700, Suren Baghdasaryan wrote:
This adds testing for polling on pidfd of a process being killed. Test runs 10000 iterations by default to stress test pidfd polling functionality. It accepts an optional command-line parameter to override the number or iterations to run. Specifically, it tests for:
- pidfd_open on a child process succeeds
- pidfd_send_signal on a child process succeeds
- polling on pidfd succeeds and returns exactly one event
- returned event is POLLIN
- event is received within 3 secs of the process being killed
10000 iterations was chosen because of the race condition being tested which is not consistently reproducible but usually is revealed after less than 2000 iterations. Reveals race fixed by commit b191d6491be6 ("pidfd: fix a poll race when setting exit_state")
Thanks for upstreaming the stress-tester. A few comments below.
Signed-off-by: Suren Baghdasaryan surenb@google.com
tools/testing/selftests/pidfd/.gitignore | 1 + tools/testing/selftests/pidfd/Makefile | 2 +- .../testing/selftests/pidfd/pidfd_poll_test.c | 137 ++++++++++++++++++ 3 files changed, 139 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/pidfd/pidfd_poll_test.c
diff --git a/tools/testing/selftests/pidfd/.gitignore b/tools/testing/selftests/pidfd/.gitignore index 16d84d117bc0..a67896347d34 100644 --- a/tools/testing/selftests/pidfd/.gitignore +++ b/tools/testing/selftests/pidfd/.gitignore @@ -1,2 +1,3 @@ pidfd_open_test +pidfd_poll_test pidfd_test diff --git a/tools/testing/selftests/pidfd/Makefile b/tools/testing/selftests/pidfd/Makefile index 720b2d884b3c..ed58b7108d18 100644 --- a/tools/testing/selftests/pidfd/Makefile +++ b/tools/testing/selftests/pidfd/Makefile @@ -1,7 +1,7 @@ # SPDX-License-Identifier: GPL-2.0-only CFLAGS += -g -I../../../../usr/include/ -lpthread -TEST_GEN_PROGS := pidfd_test pidfd_open_test +TEST_GEN_PROGS := pidfd_test pidfd_open_test pidfd_poll_test include ../lib.mk diff --git a/tools/testing/selftests/pidfd/pidfd_poll_test.c b/tools/testing/selftests/pidfd/pidfd_poll_test.c new file mode 100644 index 000000000000..f2934aa070ae --- /dev/null +++ b/tools/testing/selftests/pidfd/pidfd_poll_test.c @@ -0,0 +1,137 @@ +// SPDX-License-Identifier: GPL-2.0
+#define _GNU_SOURCE +#include <errno.h> +#include <linux/types.h> +#include <linux/wait.h> +#include <poll.h> +#include <signal.h> +#include <stdbool.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <syscall.h> +#include <sys/wait.h> +#include <unistd.h>
+#include "pidfd.h" +#include "../kselftest.h"
+#define __NR_pidfd_send_signal 424 +#define __NR_pidfd_open 434
That won't work on Alpha where this number is unfortunately different so I'm not sure which syscall you'd hit there (/me checks 424 common tgkill sys_tgkill )
The better option is to just place
#ifndef __NR_pidfd_send_signal #define __NR_pidfd_send_signal -1 #endif
#ifndef __NR_pidfd_open #define __NR_pidfd_open -1 #endif
into the pidfd.h header.
+static inline int sys_pidfd_open(pid_t pid, unsigned int flags) +{
- return syscall(__NR_pidfd_open, pid, flags);
+}
+static inline int sys_pidfd_send_signal(int pidfd, int sig, siginfo_t *info,
unsigned int flags)+{
- return syscall(__NR_pidfd_send_signal, pidfd, sig, info, flags);
+}
Those can go into pidfd.h too.
+static bool timeout;
+static void handle_alarm(int sig) +{
- timeout = true;
+}
+int main(int argc, char **argv) +{
- int ret = 1;
- int pidfd = -1;
- struct pollfd fds;
- int iter, nevents;
- int nr_iterations = 10000;
- fds.events = POLLIN;
if (argc > 2) ksft_exit_fail_msg("Unexpected command line argument");
- if (argc > 1) {
if (argc == 2)
nr_iterations = atoi(argv[1]);if (!nr_iterations) {
You should probably also check for negative values.
ksft_test_result_fail("invalid input parameter %s\n",argv[1]);return ksft_exit_fail();}- }
- ksft_print_msg("running pidfd poll test for %d iterations\n",
nr_iterations);- for (iter = 0; iter < nr_iterations; iter++) {
int child_pid = fork();if (!child_pid) {/* Child process just sleeps for a min */sleep(60);exit(0);
Just for kicks, please use exit(EXIT_SUCCESS)
}
You should switch the checkes, i.e.
if (child_pid < 0) /* do stuff */
if (child_pid == 0) /* do other stuff */
/* Parent kills the child and waits for its death */if (child_pid < 0) {if (errno == EAGAIN) {iter--;continue;}ksft_print_msg("%s - failed to fork a child process\n",strerror(errno));
Uhm, shouldn't you exit with an error here?, i.e.
ksft_exit_fail_msg(...
}pidfd = sys_pidfd_open(child_pid, 0);if (pidfd < 0) {ksft_print_msg("%s - pidfd_open failed\n",strerror(errno));goto on_error;
I think you honestly can just call ksft_exit_fail_msg() everywhere. The fds will be cleaned up on process exit anyway and it's pretty short-lived.
}/* Setup 3 sec alarm - plenty of time */if (signal(SIGALRM, handle_alarm) == SIG_ERR) {ksft_print_msg("%s - signal failed\n",strerror(errno));goto on_error;}alarm(3);/* Send SIGKILL to the child */if (sys_pidfd_send_signal(pidfd, SIGKILL, NULL, 0)) {ksft_print_msg("%s - pidfd_send_signal failed\n",strerror(errno));goto on_error;}/* Wait for the death notification */fds.fd = pidfd;nevents = poll(&fds, 1, -1);if (nevents < 0) {ksft_print_msg("%s - poll failed\n",strerror(errno));goto on_error;}if (nevents != 1) {ksft_print_msg("unexpected poll result: %d\n",nevents);goto on_error;}if (!(fds.revents & POLLIN)) {ksft_print_msg("unexpected event type received: 0x%x\n",fds.revents);goto on_error;}if (timeout) {ksft_print_msg("death notification wait timeout\n");goto on_error;}close(pidfd);- }
- ret = 0;
+on_error:
- if (pidfd)
close(pidfd);- if (ret) {
ksft_test_result_fail("failed after %d retries\n", iter);return ksft_exit_fail();- }
- ksft_test_result_pass("pidfd poll test: pass\n");
- return ksft_exit_pass();
+}
2.22.0.657.g960e92d24f-goog