From b4ad27a33d0e3b1f795ffa43d9b7dfd7ea26ee28 Mon Sep 17 00:00:00 2001
From: Oleg Nesterov <oleg@redhat.com>
Date: Thu, 2 Apr 2009 16:58:35 -0700
Subject: [PATCH] --- yaml --- r: 139708 b: refs/heads/master c:
 6dda81f4384b94930826eded254d8c16f89a9248 h: refs/heads/master v: v3

---
 [refs]                      | 2 +-
 trunk/include/linux/sched.h | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/[refs] b/[refs]
index e5966f54b842..2fe0392e6e60 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 8e654fba4a376f436bdfe361fc5cdbc87ac09b35
+refs/heads/master: 6dda81f4384b94930826eded254d8c16f89a9248
diff --git a/trunk/include/linux/sched.h b/trunk/include/linux/sched.h
index b47c94e7560b..722dd313bf8a 100644
--- a/trunk/include/linux/sched.h
+++ b/trunk/include/linux/sched.h
@@ -1489,6 +1489,11 @@ static inline struct pid *task_tgid(struct task_struct *task)
 	return task->group_leader->pids[PIDTYPE_PID].pid;
 }
 
+/*
+ * Without tasklist or rcu lock it is not safe to dereference
+ * the result of task_pgrp/task_session even if task == current,
+ * we can race with another thread doing sys_setsid/sys_setpgid.
+ */
 static inline struct pid *task_pgrp(struct task_struct *task)
 {
 	return task->group_leader->pids[PIDTYPE_PGID].pid;