sched: rt-group: optimize dequeue_rt_stack

Now that the group hierarchy can have an arbitrary depth the O(n^2) nature
of RT task dequeues will really hurt. Optimize this by providing space to
store the tree path, so we can walk it the other way.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 0a32059e6ed4..887f5db8942d 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1005,6 +1005,7 @@ struct sched_rt_entity {
         unsigned long timeout;
         int nr_cpus_allowed;
 
+        struct sched_rt_entity *back;
 #ifdef CONFIG_RT_GROUP_SCHED
         struct sched_rt_entity  *parent;
         /* rq on which this entity is (to be) queued: */