Index: linux-2.6.31-bfs/kernel/sched_bfs.c
===================================================================
--- linux-2.6.31-bfs.orig/kernel/sched_bfs.c	2009-09-08 00:07:25.564852680 +1000
+++ linux-2.6.31-bfs/kernel/sched_bfs.c	2009-09-08 21:10:01.289874772 +1000
@@ -308,9 +308,15 @@
 	return (!!p->oncpu);
 }
 
+/*
+ * Common functions for grabbing the global lock. A barrier before grabbing
+ * the lock every time is easier and safer than trying to find when to use
+ * one.
+ */
 static inline void grq_lock(void)
 	__acquires(grq.lock)
 {
+	smp_mb();
 	spin_lock(&grq.lock);
 }
 
@@ -323,6 +329,7 @@
 static inline void grq_lock_irq(void)
 	__acquires(grq.lock)
 {
+	smp_mb();
 	spin_lock_irq(&grq.lock);
 }
 
@@ -343,7 +350,7 @@
 	__acquires(grq.lock)
 {
 	local_irq_save(*flags);
-	spin_lock(&grq.lock);
+	grq_lock();
 }
 
 static inline void grq_unlock_irqrestore(unsigned long *flags)
@@ -904,16 +911,7 @@
 EXPORT_SYMBOL_GPL(kick_process);
 #endif
 
-/*
- * We need to have a special definition for an idle runqueue when testing
- * for preemption on CONFIG_HOTPLUG_CPU as the idle task may be scheduled as
- * a realtime task in sched_idle_next.
- */
-#ifdef CONFIG_HOTPLUG_CPU
-#define rq_idle(rq)	((rq)->curr == (rq)->idle && !rt_task((rq)->curr))
-#else
-#define rq_idle(rq)	((rq)->curr == (rq)->idle)
-#endif
+#define rq_idle(rq)	((rq)->queued_prio == PRIO_LIMIT)
 
 /*
  * RT tasks preempt purely on priority. SCHED_NORMAL tasks preempt on the
@@ -4803,6 +4801,15 @@
 	return group;
 }
 
+/**
+ * group_first_cpu - Returns the first cpu in the cpumask of a sched_group.
+ * @group: The group whose first cpu is to be returned.
+ */
+static inline unsigned int group_first_cpu(struct sched_group *group)
+{
+	return cpumask_first(sched_group_cpus(group));
+}
+
 #ifdef CONFIG_NUMA
 /*
  * The init_sched_build_groups can't handle what we want to do with node
@@ -4898,15 +4905,6 @@
 }
 #endif /* CONFIG_NUMA */
 
-/**
- * group_first_cpu - Returns the first cpu in the cpumask of a sched_group.
- * @group: The group whose first cpu is to be returned.
- */
-static inline unsigned int group_first_cpu(struct sched_group *group)
-{
-	return cpumask_first(sched_group_cpus(group));
-}
-
 /*
  * Initialize sched groups cpu_power.
  *