pidfd: don't do_notify_pidfd() if !thread_group_empty()

do_notify_pidfd() makes no sense until the whole thread group exits, change do_notify_parent() to check thread_group_empty(). This avoids the unnecessary do_notify_pidfd() when tsk is not a leader, or it exits before other threads, or it has a ptraced EXIT_ZOMBIE sub-thread. Signed-off-by: Oleg Nesterov <[email protected]> Link: https://lore.kernel.org/r/[email protected] Reviewed-by: Tycho Andersen <[email protected]> Signed-off-by: Christian Brauner <[email protected]>
wafgo · Feb 2, 2024 · 21e2520 · 21e2520
1 parent cdefbf2
commit 21e2520
Showing 1 changed file with 5 additions and 3 deletions.
diff --git a/kernel/signal.c b/kernel/signal.c
@@ -2050,9 +2050,11 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
 
 	WARN_ON_ONCE(!tsk->ptrace &&
 	       (tsk->group_leader != tsk || !thread_group_empty(tsk)));
-
-	/* Wake up all pidfd waiters */
-	do_notify_pidfd(tsk);
+	/*
+	 * tsk is a group leader and has no threads, wake up the pidfd waiters.
+	 */
+	if (thread_group_empty(tsk))
+		do_notify_pidfd(tsk);
 
 	if (sig != SIGCHLD) {
 		/*