From 3884ae44f41247e0ae41952d4fad46db86d2e0a8 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Tue, 23 Jul 2019 10:08:28 +0200 Subject: [PATCH 1/3] pidfd: remove obsolete comments from test Since the introduction of CLONE_PIDFD pidfd_send_signal() is independent of CONFIG_PROC_FS. Signed-off-by: Christian Brauner --- tools/testing/selftests/pidfd/pidfd_test.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) diff --git a/tools/testing/selftests/pidfd/pidfd_test.c b/tools/testing/selftests/pidfd/pidfd_test.c index 7eaa8a3de262..b632965e60eb 100644 --- a/tools/testing/selftests/pidfd/pidfd_test.c +++ b/tools/testing/selftests/pidfd/pidfd_test.c @@ -339,13 +339,9 @@ static int test_pidfd_send_signal_syscall_support(void) ret = sys_pidfd_send_signal(pidfd, 0, NULL, 0); if (ret < 0) { - /* - * pidfd_send_signal() will currently return ENOSYS when - * CONFIG_PROC_FS is not set. - */ if (errno == ENOSYS) ksft_exit_skip( - "%s test: pidfd_send_signal() syscall not supported (Ensure that CONFIG_PROC_FS=y is set)\n", + "%s test: pidfd_send_signal() syscall not supported\n", test_name); ksft_exit_fail_msg("%s test: Failed to send signal\n", From 1caf7d50f46bd0388e38e653b146aa81700e8eb8 Mon Sep 17 00:00:00 2001 From: "Joel Fernandes (Google)" Date: Wed, 24 Jul 2019 12:48:16 -0400 Subject: [PATCH 2/3] pidfd: Add warning if exit_state is 0 during notification Previously a condition got missed where the pidfd waiters are awakened before the exit_state gets set. This can result in a missed notification [1] and the polling thread waiting forever. It is fixed now, however it would be nice to avoid this kind of issue going unnoticed in the future. So just add a warning to catch it in the future. /* References */ [1]: https://lore.kernel.org/lkml/20190717172100.261204-1-joel@joelfernandes.org/ Signed-off-by: Joel Fernandes (Google) Link: https://lore.kernel.org/r/20190724164816.201099-1-joel@joelfernandes.org Signed-off-by: Christian Brauner --- kernel/signal.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/signal.c b/kernel/signal.c index 91b789dd6e72..349f5a67f100 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1885,6 +1885,7 @@ static void do_notify_pidfd(struct task_struct *task) { struct pid *pid; + WARN_ON(task->exit_state == 0); pid = task_pid(task); wake_up_all(&pid->wait_pidfd); } From 30b692d3b390c6fe78a5064be0c4bbd44a41be59 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Mon, 29 Jul 2019 17:48:24 +0200 Subject: [PATCH 3/3] exit: make setting exit_state consistent Since commit b191d6491be6 ("pidfd: fix a poll race when setting exit_state") we unconditionally set exit_state to EXIT_ZOMBIE before calling into do_notify_parent(). This was done to eliminate a race when querying exit_state in do_notify_pidfd(). Back then we decided to do the absolute minimal thing to fix this and not touch the rest of the exit_notify() function where exit_state is set. Since this fix has not caused any issues change the setting of exit_state to EXIT_DEAD in the autoreap case to account for the fact hat exit_state is set to EXIT_ZOMBIE unconditionally. This fix was planned but also explicitly requested in [1] and makes the whole code more consistent. /* References */ [1]: https://lore.kernel.org/lkml/CAHk-=wigcxGFR2szue4wavJtH5cYTTeNES=toUBVGsmX0rzX+g@mail.gmail.com Signed-off-by: Christian Brauner Acked-by: Oleg Nesterov Cc: Linus Torvalds --- kernel/exit.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index 4436158a6d30..5b4a5dcce8f8 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -734,9 +734,10 @@ static void exit_notify(struct task_struct *tsk, int group_dead) autoreap = true; } - tsk->exit_state = autoreap ? EXIT_DEAD : EXIT_ZOMBIE; - if (tsk->exit_state == EXIT_DEAD) + if (autoreap) { + tsk->exit_state = EXIT_DEAD; list_add(&tsk->ptrace_entry, &dead); + } /* mt-exec, de_thread() is waiting for group leader */ if (unlikely(tsk->signal->notify_count < 0))