[patch] sched,cgroup_sched: fix up task_groups list buglet

[Mike Galbraith <efault@gmx.de>]

On Tue, 2012-04-03 at 11:19 +0200, Mike Galbraith wrote: 
> ec514c48 made rt queues invisible in sched_debug, restore visibility.

<g> removing their cloak of invisibility might be a tad better than just
making them visible while futzing with annoying RT_GROUP_SCHED throttle.

sched,cgroup_sched: fix up task_groups list

Oops happened during sched migration to kernel/sched, fix it up.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: stable@kernel.org # v3.3
---
 kernel/sched/core.c  |    1 +
 kernel/sched/sched.h |    2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6871,6 +6871,7 @@ int in_sched_functions(unsigned long add
 
 #ifdef CONFIG_CGROUP_SCHED
 struct task_group root_task_group;
+LIST_HEAD(task_groups);
 #endif
 
 DECLARE_PER_CPU(cpumask_var_t, load_balance_tmpmask);
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -80,7 +80,7 @@ extern struct mutex sched_domains_mutex;
 struct cfs_rq;
 struct rt_rq;
 
-static LIST_HEAD(task_groups);
+extern struct list_head task_groups;
 
 struct cfs_bandwidth {
 #ifdef CONFIG_CFS_BANDWIDTH