[PATCH] zap_pid_ns_processes: clear TIF_NOTIFY_SIGNAL along with TIF_SIGPENDING

Oleg Nesterov
2024-06-08T12:08:02Z

kernel_wait4() doesn't sleep and returns -EINTR if there is no
eligible child and signal_pending() is true.

That is why zap_pid_ns_processes() clears TIF_SIGPENDING but this is not
enough, it should also clear TIF_NOTIFY_SIGNAL to make signal_pending()
return false and avoid a busy-wait loop.

Fixes: 12db8b690010 ("entry: Add support for TIF_NOTIFY_SIGNAL")
Reported-by: Rachel Menge <rachelmenge@linux.microsoft.com>
Closes: https://lore.kernel.org/all/1386cd49-36d0-4a5c-85e9-bc42056a5a38@linux.microsoft.com/
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
kernel/pid_namespace.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index dc48fecfa1dc..25f3cf679b35 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -218,6 +218,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
*/
do {
clear_thread_flag(TIF_SIGPENDING);
+ clear_thread_flag(TIF_NOTIFY_SIGNAL);
rc = kernel_wait4(-1, NULL, __WALL, NULL);
} while (rc != -ECHILD);

--
2.25.1.362.g51ebf55