[PATCH] sched: Filter root_task_group at the beginning

[Haifeng Xu]

We can't change the weight of the root cgroup. Let's handle
root_task_group before doing any real work including acquiring
the shares_mutex.

Signed-off-by: Haifeng Xu <haifeng.xu@xxxxxxxxxx>
---
 kernel/sched/fair.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a80a73909dc2..1ac2df87e070 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -12594,6 +12594,9 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
 {
 	int ret;
 
+	if (tg == &root_task_group)
+		return -EINVAL;
+
 	mutex_lock(&shares_mutex);
 	if (tg_is_idle(tg))
 		ret = -EINVAL;
-- 
2.25.1