@@ -428,26 +428,37 @@ TEST_F(pidfd_info, thread_group_exec)
ASSERT_GE(pidfd_leader_thread, 0);
/*
- * We can poll and wait for the old thread-group leader to exit
- * using a thread-specific pidfd.
+ * We can't poll and wait for the old thread-group leader to exit
+ * using a thread-specific pidfd. The thread-group leader exited
+ * prematurely and notification is delayed until all subthreads
+ * have exited.
*
- * This only works until the thread has execed. When the thread
- * has execed it will have taken over the old thread-group
- * leaders struct pid. Calling poll after the thread execed will
- * thus block again because a new thread-group has started (Yes,
- * it's fscked.).
+ * When the thread has execed it will taken over the old
+ * thread-group leaders struct pid. Calling poll after the
+ * thread execed will thus block again because a new
+ * thread-group has started.
*/
fds.events = POLLIN;
fds.fd = pidfd_leader_thread;
- nevents = poll(&fds, 1, -1);
- ASSERT_EQ(nevents, 1);
- /* The thread-group leader has exited. */
- ASSERT_TRUE(!!(fds.revents & POLLIN));
+ nevents = poll(&fds, 1, 2000 /* wait 2 seconds */);
+ ASSERT_EQ(nevents, 0);
+ /* The thread-group leader has exited but there's still a live subthread. */
+ ASSERT_FALSE(!!(fds.revents & POLLIN));
/* The thread-group leader hasn't been reaped. */
ASSERT_FALSE(!!(fds.revents & POLLHUP));
/* Now that we've opened a thread-specific pidfd the thread can exec. */
ASSERT_EQ(write_nointr(ipc_sockets[0], &pid_thread, sizeof(pid_thread)), sizeof(pid_thread));
+
+ fds.events = POLLIN;
+ fds.fd = pidfd_leader_thread;
+ nevents = poll(&fds, 1, 2000 /* wait 2 seconds */);
+ ASSERT_EQ(nevents, 0);
+ /* The thread-group leader has exited but there's still a live subthread. */
+ ASSERT_FALSE(!!(fds.revents & POLLIN));
+ /* The thread-group leader hasn't been reaped. */
+ ASSERT_FALSE(!!(fds.revents & POLLHUP));
+
EXPECT_EQ(close(ipc_sockets[0]), 0);
/* Wait until the kernel has SIGKILLed the thread. */
@@ -482,6 +493,20 @@ TEST_F(pidfd_info, thread_group_exec)
/* Take down the thread-group leader. */
EXPECT_EQ(sys_pidfd_send_signal(pidfd_leader, SIGKILL, NULL, 0), 0);
+
+ /*
+ * Afte the exec we're dealing with an empty thread-group so now
+ * we must see an exit notification on the thread-specific pidfd
+ * for the thread-group leader as there's no subthread that can
+ * revive the struct pid.
+ */
+ fds.events = POLLIN;
+ fds.fd = pidfd_leader_thread;
+ nevents = poll(&fds, 1, -1);
+ ASSERT_EQ(nevents, 1);
+ ASSERT_TRUE(!!(fds.revents & POLLIN));
+ ASSERT_FALSE(!!(fds.revents & POLLHUP));
+
EXPECT_EQ(sys_waitid(P_PIDFD, pidfd_leader, NULL, WEXITED), 0);
/* Retrieve exit information for the thread-group leader. */
Ensure that during a multi-threaded exec and premature thread-group leader exit no exit notification is generated. Signed-off-by: Christian Brauner <brauner@kernel.org> --- tools/testing/selftests/pidfd/pidfd_info_test.c | 47 +++++++++++++++++++------ 1 file changed, 36 insertions(+), 11 deletions(-)