[PATCH v2 4/4] tests: add waitid() tests for non-blocking pidfds

Christian Brauner
2020-09-02T10:23:27Z

Verify that the PIDFD_NONBLOCK flag works with pidfd_open() and that
waitid() with a non-blocking pidfd returns EAGAIN:

TAP version 13
1..3
# Starting 3 tests from 1 test cases.
# RUN global.wait_simple ...
# OK global.wait_simple
ok 1 global.wait_simple
# RUN global.wait_states ...
# OK global.wait_states
ok 2 global.wait_states
# RUN global.wait_nonblock ...
# OK global.wait_nonblock
ok 3 global.wait_nonblock
# PASSED: 3 / 3 tests passed.
# Totals: pass:3 fail:0 xfail:0 xpass:0 skip:0 error:0

Cc: Shuah Khan <shuah@kernel.org>
Cc: linux-kselftest@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v2 */
unchanged
---
tools/testing/selftests/pidfd/pidfd.h | 4 ++
tools/testing/selftests/pidfd/pidfd_wait.c | 83 +++++++++++++++++++++-
2 files changed, 86 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/pidfd/pidfd.h b/tools/testing/selftests/pidfd/pidfd.h
index a2c80914e3dc..01f8d3c0cf2c 100644
--- a/tools/testing/selftests/pidfd/pidfd.h
+++ b/tools/testing/selftests/pidfd/pidfd.h
@@ -46,6 +46,10 @@
#define __NR_pidfd_getfd -1
#endif

+#ifndef PIDFD_NONBLOCK
+#define PIDFD_NONBLOCK O_NONBLOCK
+#endif
+
/*
* The kernel reserves 300 pids via RESERVED_PIDS in kernel/pid.c
* That means, when it wraps around any pid < 300 will be skipped.
diff --git a/tools/testing/selftests/pidfd/pidfd_wait.c b/tools/testing/selftests/pidfd/pidfd_wait.c
index 075c716f6fb8..cefce4d3d2f6 100644
--- a/tools/testing/selftests/pidfd/pidfd_wait.c
+++ b/tools/testing/selftests/pidfd/pidfd_wait.c
@@ -21,6 +21,11 @@

#define ptr_to_u64(ptr) ((__u64)((uintptr_t)(ptr)))

+/* Attempt to de-conflict with the selftests tree. */
+#ifndef SKIP
+#define SKIP(s, ...) XFAIL(s, ##__VA_ARGS__)
+#endif
+
static pid_t sys_clone3(struct clone_args *args)
{
return syscall(__NR_clone3, args, sizeof(struct clone_args));
@@ -65,7 +70,7 @@ TEST(wait_simple)
pidfd = -1;

pid = sys_clone3(&args);
- ASSERT_GE(pid, 1);
+ ASSERT_GE(pid, 0);

if (pid == 0)
exit(EXIT_SUCCESS);
@@ -133,4 +138,80 @@ TEST(wait_states)
EXPECT_EQ(close(pidfd), 0);
}

+TEST(wait_nonblock)
+{
+ int pidfd, status = 0;
+ unsigned int flags = 0;
+ pid_t parent_tid = -1;
+ struct clone_args args = {
+ .parent_tid = ptr_to_u64(&parent_tid),
+ .flags = CLONE_PARENT_SETTID,
+ .exit_signal = SIGCHLD,
+ };
+ int ret;
+ pid_t pid;
+ siginfo_t info = {
+ .si_signo = 0,
+ };
+
+ /*
+ * Callers need to see ECHILD with non-blocking pidfds when no child
+ * processes exists.
+ */
+ pidfd = sys_pidfd_open(getpid(), PIDFD_NONBLOCK);
+ EXPECT_GE(pidfd, 0) {
+ /* pidfd_open() doesn't support PIDFD_NONBLOCK. */
+ ASSERT_EQ(errno, EINVAL);
+ SKIP(return, "Skipping PIDFD_NONBLOCK test");
+ }
+
+ pid = sys_waitid(P_PIDFD, pidfd, &info, WEXITED, NULL);
+ ASSERT_LT(pid, 0);
+ ASSERT_EQ(errno, ECHILD);
+ EXPECT_EQ(close(pidfd), 0);
+
+ pid = sys_clone3(&args);
+ ASSERT_GE(pid, 0);
+
+ if (pid == 0) {
+ kill(getpid(), SIGSTOP);
+ exit(EXIT_SUCCESS);
+ }
+
+ pidfd = sys_pidfd_open(pid, PIDFD_NONBLOCK);
+ EXPECT_GE(pidfd, 0) {
+ /* pidfd_open() doesn't support PIDFD_NONBLOCK. */
+ ASSERT_EQ(errno, EINVAL);
+ SKIP(return, "Skipping PIDFD_NONBLOCK test");
+ }
+
+ flags = fcntl(pidfd, F_GETFL, 0);
+ ASSERT_GT(flags, 0);
+ ASSERT_GT((flags & O_NONBLOCK), 0);
+
+ /*
+ * Callers need to see EAGAIN/EWOULDBLOCK with non-blocking pidfd when
+ * child processes exist but none have exited.
+ */
+ pid = sys_waitid(P_PIDFD, pidfd, &info, WEXITED, NULL);
+ ASSERT_LT(pid, 0);
+ ASSERT_EQ(errno, EAGAIN);
+
+ ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WSTOPPED, NULL), 0);
+ ASSERT_EQ(info.si_signo, SIGCHLD);
+ ASSERT_EQ(info.si_code, CLD_STOPPED);
+ ASSERT_EQ(info.si_pid, parent_tid);
+
+ ASSERT_EQ(sys_pidfd_send_signal(pidfd, SIGCONT, NULL, 0), 0);
+
+ ASSERT_EQ(fcntl(pidfd, F_SETFL, (flags & ~O_NONBLOCK)), 0);
+
+ ASSERT_EQ(sys_waitid(P_PIDFD, pidfd, &info, WEXITED, NULL), 0);
+ ASSERT_EQ(info.si_signo, SIGCHLD);
+ ASSERT_EQ(info.si_code, CLD_EXITED);
+ ASSERT_EQ(info.si_pid, parent_tid);
+
+ EXPECT_EQ(close(pidfd), 0);
+}
+
TEST_HARNESS_MAIN
--
2.28.0