---
 kernel/sched.c |   26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

Index: linux-2.6.20.2-rsdl/kernel/sched.c
===================================================================
--- linux-2.6.20.2-rsdl.orig/kernel/sched.c	2007-03-12 10:46:56.000000000 +1100
+++ linux-2.6.20.2-rsdl/kernel/sched.c	2007-03-12 10:47:20.000000000 +1100
@@ -17,7 +17,7 @@
  *  2003-09-03	Interactivity tuning by Con Kolivas.
  *  2004-04-02	Scheduler domains code by Nick Piggin
  *  2007-03-02	Rotating Staircase deadline scheduling policy by Con Kolivas
- *		RSDL v0.29
+ *		RSDL v0.30
  */
 
 #include <linux/mm.h>
@@ -85,10 +85,9 @@
  * provided it is not a realtime comparison.
  */
 #define TASK_PREEMPTS_CURR(p, curr) \
-	(((p)->prio < (curr)->prio) || (((p)->prio == (curr)->prio) && \
+	(((p)->prio < (curr)->prio) || (!rt_task(p) && \
 		((p)->static_prio < (curr)->static_prio && \
-			((curr)->static_prio > (curr)->prio)) && \
-				!rt_task(p)))
+			((curr)->static_prio > (curr)->prio))))
 
 /*
  * This is the time all tasks within the same priority round robin.
@@ -3089,7 +3088,7 @@ static inline void major_prio_rotation(s
  */
 static inline void rotate_runqueue_priority(struct rq *rq)
 {
-	int new_prio_level, remaining_quota;
+	int new_prio_level;
 	struct prio_array *array;
 
 	/*
@@ -3100,7 +3099,6 @@ static inline void rotate_runqueue_prior
 	if (unlikely(sched_find_first_bit(rq->dyn_bitmap) < rq->prio_level))
 		return;
 
-	remaining_quota = rq_quota(rq, rq->prio_level);
 	array = rq->active;
 	if (rq->prio_level > MAX_PRIO - 2) {
 		/* Major rotation required */
@@ -3134,10 +3132,11 @@ static inline void rotate_runqueue_prior
 	}
 	rq->prio_level = new_prio_level;
 	/*
-	 * While we usually rotate with the rq quota being 0, it is possible
-	 * to be negative so we subtract any deficit from the new level.
+	 * As we are merging to a prio_level that may not have anything in
+	 * its quota we add 1 to ensure the tasks get to run in schedule() to
+	 * add their quota to it.
 	 */
-	rq_quota(rq, new_prio_level) += remaining_quota;
+	rq_quota(rq, new_prio_level) += 1;
 }
 
 static void task_running_tick(struct rq *rq, struct task_struct *p)
@@ -3163,12 +3162,11 @@ static void task_running_tick(struct rq 
 	if (!--p->time_slice)
 		task_expired_entitlement(rq, p);
 	/*
-	 * The rq quota can become negative due to a task being queued in
-	 * scheduler without any quota left at that priority level. It is
-	 * cheaper to allow it to run till this scheduler tick and then
-	 * subtract it from the quota of the merged queues.
+	 * We only employ the deadline mechanism if we run over the quota.
+	 * It allows aliasing problems around the scheduler_tick to be
+	 * less harmful.
 	 */
-	if (!rt_task(p) && --rq_quota(rq, rq->prio_level) <= 0) {
+	if (!rt_task(p) && --rq_quota(rq, rq->prio_level) < 0) {
 		if (unlikely(p->first_time_slice))
 			p->first_time_slice = 0;
 		rotate_runqueue_priority(rq);