commit af4b8a83add95ef40716401395b44a1b579965f4
author Eric W. Biederman <ebiederm@xmission.com> Wed Aug 01 15:03:42 2012 -0700
committer Eric W. Biederman <ebiederm@xmission.com> Mon Nov 19 05:59:12 2012 -0800
tree 2f3f606b7327f74c1c1beb8a75886318c51c838a
parent 5e1182deb81ae8c68494017c4a8a71811659c870

pidns: Wait in zap_pid_ns_processes until pid_ns->nr_hashed == 1

Looking at pid_ns->nr_hashed is a bit simpler and it works for
disjoint process trees that an unshare or a join of a pid_namespace
may create.

Acked-by: "Serge E. Hallyn" <serge@hallyn.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

kernel/pid_namespace.c

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index 84591cf..3cc29b8 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -217,22 +217,15 @@
 
 	/*
 	 * sys_wait4() above can't reap the TASK_DEAD children.
-	 * Make sure they all go away, see __unhash_process().
+	 * Make sure they all go away, see free_pid().
 	 */
 	for (;;) {
-		bool need_wait = false;
-
-		read_lock(&tasklist_lock);
-		if (!list_empty(&current->children)) {
-			__set_current_state(TASK_UNINTERRUPTIBLE);
-			need_wait = true;
-		}
-		read_unlock(&tasklist_lock);
-
-		if (!need_wait)
+		set_current_state(TASK_UNINTERRUPTIBLE);
+		if (pid_ns->nr_hashed == 1)
 			break;
 		schedule();
 	}
+	__set_current_state(TASK_RUNNING);
 
 	if (pid_ns->reboot)
 		current->signal->group_exit_code = pid_ns->reboot;