From 2eb2d932e894c03b436e409001009be5eebbeeee Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Sat, 19 Apr 2008 19:45:00 +0200
Subject: [PATCH] --- yaml --- r: 91097 b: refs/heads/master c:
 58d6c2d72f8628f39e8689fbde8aa177fcf00a37 h: refs/heads/master i:   91095:
 86774383597ebaebe21c81ef1815c1f02f6418f1 v: v3

---
 [refs]                      |  2 +-
 trunk/include/linux/sched.h |  1 +
 trunk/kernel/sched_rt.c     | 27 +++++++++++----------------
 3 files changed, 13 insertions(+), 17 deletions(-)

diff --git a/[refs] b/[refs]
index a51972ae55b7..84b7ef309455 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: d19ca30874f2ad343d054e0b5c0576744afeecd4
+refs/heads/master: 58d6c2d72f8628f39e8689fbde8aa177fcf00a37
diff --git a/trunk/include/linux/sched.h b/trunk/include/linux/sched.h
index 0a32059e6ed4..887f5db8942d 100644
--- a/trunk/include/linux/sched.h
+++ b/trunk/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: */
diff --git a/trunk/kernel/sched_rt.c b/trunk/kernel/sched_rt.c
index 736fb8fd8977..c2730a5a4f05 100644
--- a/trunk/kernel/sched_rt.c
+++ b/trunk/kernel/sched_rt.c
@@ -479,26 +479,21 @@ static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
 /*
  * Because the prio of an upper entry depends on the lower
  * entries, we must remove entries top - down.
- *
- * XXX: O(1/2 h^2) because we can only walk up, not down the chain.
  */
 static void dequeue_rt_stack(struct task_struct *p)
 {
-	struct sched_rt_entity *rt_se, *top_se;
+	struct sched_rt_entity *rt_se, *back = NULL;
 
-	/*
-	 * dequeue all, top - down.
-	 */
-	do {
-		rt_se = &p->rt;
-		top_se = NULL;
-		for_each_sched_rt_entity(rt_se) {
-			if (on_rt_rq(rt_se))
-				top_se = rt_se;
-		}
-		if (top_se)
-			dequeue_rt_entity(top_se);
-	} while (top_se);
+	rt_se = &p->rt;
+	for_each_sched_rt_entity(rt_se) {
+		rt_se->back = back;
+		back = rt_se;
+	}
+
+	for (rt_se = back; rt_se; rt_se = rt_se->back) {
+		if (on_rt_rq(rt_se))
+			dequeue_rt_entity(rt_se);
+	}
 }
 
 /*