commit 2ceb8693ef63ae3d154ce1a05d275f2bb20a5e4c
author Oleg Nesterov <oleg@tv-sign.ru> Mon Jun 26 00:26:04 2006 -0700
committer Linus Torvalds <torvalds@g5.osdl.org> Mon Jun 26 09:58:26 2006 -0700
tree 6e61f8c5513cb905d6326417b0e95f27d3623735
parent 42c3e03ef6b298813557cdb997bd6db619cd65a2

[PATCH] de_thread: fix lockless do_each_thread

We should keep the value of old_leader->tasks.next in de_thread, otherwise
we can't do for_each_process/do_each_thread without tasklist_lock held.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/exec.c

diff --git a/fs/exec.c b/fs/exec.c
index 8c51960..fffea1e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -707,7 +707,7 @@
 		attach_pid(current, PIDTYPE_PID,  current->pid);
 		attach_pid(current, PIDTYPE_PGID, current->signal->pgrp);
 		attach_pid(current, PIDTYPE_SID,  current->signal->session);
-		list_add_tail_rcu(&current->tasks, &init_task.tasks);
+		list_replace_rcu(&leader->tasks, &current->tasks);
 
 		current->group_leader = current;
 		leader->group_leader = current;
@@ -715,7 +715,6 @@
 		/* Reduce leader to a thread */
 		detach_pid(leader, PIDTYPE_PGID);
 		detach_pid(leader, PIDTYPE_SID);
-		list_del_init(&leader->tasks);
 
 		current->exit_signal = SIGCHLD;