From 78975bddf5fddf44f1b43e9aba5d9d36221a3f82 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Thu, 15 Jan 2009 14:53:38 +0100
Subject: [PATCH] --- yaml --- r: 129814 b: refs/heads/master c:
 6bc912b71b6f33b041cfde93ca3f019cbaa852bc h: refs/heads/master v: v3

---
 [refs]                    |  2 +-
 trunk/kernel/sched_fair.c | 30 ++++++++++++++++++++++--------
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/[refs] b/[refs]
index f9765dd13ef4..5fd7801a0b2c 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: cce7ade803699463ecc62a065ca522004f7ccb3d
+refs/heads/master: 6bc912b71b6f33b041cfde93ca3f019cbaa852bc
diff --git a/trunk/kernel/sched_fair.c b/trunk/kernel/sched_fair.c
index 8e1352c75557..cdebd8089cb0 100644
--- a/trunk/kernel/sched_fair.c
+++ b/trunk/kernel/sched_fair.c
@@ -677,9 +677,13 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
 			unsigned long thresh = sysctl_sched_latency;
 
 			/*
-			 * convert the sleeper threshold into virtual time
+			 * Convert the sleeper threshold into virtual time.
+			 * SCHED_IDLE is a special sub-class.  We care about
+			 * fairness only relative to other SCHED_IDLE tasks,
+			 * all of which have the same weight.
 			 */
-			if (sched_feat(NORMALIZED_SLEEPER))
+			if (sched_feat(NORMALIZED_SLEEPER) &&
+					task_of(se)->policy != SCHED_IDLE)
 				thresh = calc_delta_fair(thresh, se);
 
 			vruntime -= thresh;
@@ -1340,14 +1344,18 @@ wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
 
 static void set_last_buddy(struct sched_entity *se)
 {
-	for_each_sched_entity(se)
-		cfs_rq_of(se)->last = se;
+	if (likely(task_of(se)->policy != SCHED_IDLE)) {
+		for_each_sched_entity(se)
+			cfs_rq_of(se)->last = se;
+	}
 }
 
 static void set_next_buddy(struct sched_entity *se)
 {
-	for_each_sched_entity(se)
-		cfs_rq_of(se)->next = se;
+	if (likely(task_of(se)->policy != SCHED_IDLE)) {
+		for_each_sched_entity(se)
+			cfs_rq_of(se)->next = se;
+	}
 }
 
 /*
@@ -1393,12 +1401,18 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
 		return;
 
 	/*
-	 * Batch tasks do not preempt (their preemption is driven by
+	 * Batch and idle tasks do not preempt (their preemption is driven by
 	 * the tick):
 	 */
-	if (unlikely(p->policy == SCHED_BATCH))
+	if (unlikely(p->policy != SCHED_NORMAL))
 		return;
 
+	/* Idle tasks are by definition preempted by everybody. */
+	if (unlikely(curr->policy == SCHED_IDLE)) {
+		resched_task(curr);
+		return;
+	}
+
 	if (!sched_feat(WAKEUP_PREEMPT))
 		return;