linux-kernel - [PATCH] processes: reparent_thread: don't call kill_orphaned_pgrp() if task

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Message-ID: <20081120202848.GA27241@redhat.com>
Date:	Thu, 20 Nov 2008 21:28:48 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Roland McGrath <roland@...hat.com>
Cc:	Pavel Emelyanov <xemul@...nvz.org>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] processes: reparent_thread: don't call
	kill_orphaned_pgrp() if task_detached()

Needs an ack from someone who understands orphaned groups.

If task_detached(p) == T, then either

	a) p is not the main thread, we will find the group leader
	   on the ->children list.
or
	b) p is the group leader but its ->exit_state = EXIT_DEAD.
	   This can only happen when the last sub-thread has died,
	   but in that case that thread has already called
	   kill_orphaned_pgrp() from exit_notify().

In both cases kill_orphaned_pgrp() looks bogus.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>

--- K-28/kernel/exit.c~1_IGNORE_DETACHED	2008-11-17 02:02:12.000000000 +0100
+++ K-28/kernel/exit.c	2008-11-20 20:21:02.000000000 +0100
@@ -816,6 +816,8 @@ static void reparent_thread(struct task_
 
 	list_move_tail(&p->sibling, &p->real_parent->children);
 
+	if (task_detached(p))
+		return;
 	/* If this is a threaded reparent there is no need to
 	 * notify anyone anything has happened.
 	 */
@@ -823,15 +825,13 @@ static void reparent_thread(struct task_
 		return;
 
 	/* We don't want people slaying init.  */
-	if (!task_detached(p))
-		p->exit_signal = SIGCHLD;
+	p->exit_signal = SIGCHLD;
 
 	/* If we'd notified the old parent about this child's death,
 	 * also notify the new parent.
 	 */
 	if (!ptrace_reparented(p) &&
-	    p->exit_state == EXIT_ZOMBIE &&
-	    !task_detached(p) && thread_group_empty(p))
+	    p->exit_state == EXIT_ZOMBIE && thread_group_empty(p))
 		do_notify_parent(p, p->exit_signal);
 
 	kill_orphaned_pgrp(p, father);

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