X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=kernel%2Fsched_rt.c;h=4d0a60e47dfab5e06405cffbd803a1ededd4708e;hb=7f51f298204ec0528422cd9b23feac12612c5665;hp=d0097a0634e54f3dfcce71da006359c6d22d5b01;hpb=541010e4b8921cd781ff02ae68028501457045b6;p=linux-2.6

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index d0097a0634..4d0a60e47d 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -3,6 +3,52 @@
  * policies)
  */
 
+#ifdef CONFIG_SMP
+
+/*
+ * The "RT overload" flag: it gets set if a CPU has more than
+ * one runnable RT task.
+ */
+static cpumask_t rt_overload_mask;
+static atomic_t rto_count;
+
+static inline int rt_overloaded(void)
+{
+	return atomic_read(&rto_count);
+}
+
+static inline void rt_set_overload(struct rq *rq)
+{
+	rq->rt.overloaded = 1;
+	cpu_set(rq->cpu, rt_overload_mask);
+	/*
+	 * Make sure the mask is visible before we set
+	 * the overload count. That is checked to determine
+	 * if we should look at the mask. It would be a shame
+	 * if we looked at the mask, but the mask was not
+	 * updated yet.
+	 */
+	wmb();
+	atomic_inc(&rto_count);
+}
+
+static inline void rt_clear_overload(struct rq *rq)
+{
+	/* the order here really doesn't matter */
+	atomic_dec(&rto_count);
+	cpu_clear(rq->cpu, rt_overload_mask);
+	rq->rt.overloaded = 0;
+}
+
+static void update_rt_migration(struct rq *rq)
+{
+	if (rq->rt.rt_nr_migratory && (rq->rt.rt_nr_running > 1))
+		rt_set_overload(rq);
+	else
+		rt_clear_overload(rq);
+}
+#endif /* CONFIG_SMP */
+
 /*
  * Update the current task's runtime statistics. Skip current tasks that
  * are not in our scheduling class.
@@ -23,6 +69,46 @@ static void update_curr_rt(struct rq *rq)
 
 	curr->se.sum_exec_runtime += delta_exec;
 	curr->se.exec_start = rq->clock;
+	cpuacct_charge(curr, delta_exec);
+}
+
+static inline void inc_rt_tasks(struct task_struct *p, struct rq *rq)
+{
+	WARN_ON(!rt_task(p));
+	rq->rt.rt_nr_running++;
+#ifdef CONFIG_SMP
+	if (p->prio < rq->rt.highest_prio)
+		rq->rt.highest_prio = p->prio;
+	if (p->nr_cpus_allowed > 1)
+		rq->rt.rt_nr_migratory++;
+
+	update_rt_migration(rq);
+#endif /* CONFIG_SMP */
+}
+
+static inline void dec_rt_tasks(struct task_struct *p, struct rq *rq)
+{
+	WARN_ON(!rt_task(p));
+	WARN_ON(!rq->rt.rt_nr_running);
+	rq->rt.rt_nr_running--;
+#ifdef CONFIG_SMP
+	if (rq->rt.rt_nr_running) {
+		struct rt_prio_array *array;
+
+		WARN_ON(p->prio < rq->rt.highest_prio);
+		if (p->prio == rq->rt.highest_prio) {
+			/* recalculate */
+			array = &rq->rt.active;
+			rq->rt.highest_prio =
+				sched_find_first_bit(array->bitmap);
+		} /* otherwise leave rq->highest prio alone */
+	} else
+		rq->rt.highest_prio = MAX_RT_PRIO;
+	if (p->nr_cpus_allowed > 1)
+		rq->rt.rt_nr_migratory--;
+
+	update_rt_migration(rq);
+#endif /* CONFIG_SMP */
 }
 
 static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
@@ -31,6 +117,9 @@ static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
 
 	list_add_tail(&p->run_list, array->queue + p->prio);
 	__set_bit(p->prio, array->bitmap);
+	inc_cpu_load(rq, p->se.load.weight);
+
+	inc_rt_tasks(p, rq);
 }
 
 /*
@@ -45,6 +134,9 @@ static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
 	list_del(&p->run_list);
 	if (list_empty(array->queue + p->prio))
 		__clear_bit(p->prio, array->bitmap);
+	dec_cpu_load(rq, p->se.load.weight);
+
+	dec_rt_tasks(p, rq);
 }
 
 /*
@@ -64,6 +156,45 @@ yield_task_rt(struct rq *rq)
 	requeue_task_rt(rq, rq->curr);
 }
 
+#ifdef CONFIG_SMP
+static int find_lowest_rq(struct task_struct *task);
+
+static int select_task_rq_rt(struct task_struct *p, int sync)
+{
+	struct rq *rq = task_rq(p);
+
+	/*
+	 * If the current task is an RT task, then
+	 * try to see if we can wake this RT task up on another
+	 * runqueue. Otherwise simply start this RT task
+	 * on its current runqueue.
+	 *
+	 * We want to avoid overloading runqueues. Even if
+	 * the RT task is of higher priority than the current RT task.
+	 * RT tasks behave differently than other tasks. If
+	 * one gets preempted, we try to push it off to another queue.
+	 * So trying to keep a preempting RT task on the same
+	 * cache hot CPU will force the running RT task to
+	 * a cold CPU. So we waste all the cache for the lower
+	 * RT task in hopes of saving some of a RT task
+	 * that is just being woken and probably will have
+	 * cold cache anyway.
+	 */
+	if (unlikely(rt_task(rq->curr)) &&
+	    (p->nr_cpus_allowed > 1)) {
+		int cpu = find_lowest_rq(p);
+
+		return (cpu == -1) ? task_cpu(p) : cpu;
+	}
+
+	/*
+	 * Otherwise, just let it ride on the affined RQ and the
+	 * post-schedule router will push the preempted task away
+	 */
+	return task_cpu(p);
+}
+#endif /* CONFIG_SMP */
+
 /*
  * Preempt the current task with a newly woken task if needed:
  */
@@ -98,104 +229,566 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
 	p->se.exec_start = 0;
 }
 
-/*
- * Load-balancing iterator. Note: while the runqueue stays locked
- * during the whole iteration, the current task might be
- * dequeued so the iterator has to be dequeue-safe. Here we
- * achieve that by always pre-iterating before returning
- * the current task:
- */
-static struct task_struct *load_balance_start_rt(void *arg)
+#ifdef CONFIG_SMP
+/* Only try algorithms three times */
+#define RT_MAX_TRIES 3
+
+static int double_lock_balance(struct rq *this_rq, struct rq *busiest);
+static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep);
+
+static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
+{
+	if (!task_running(rq, p) &&
+	    (cpu < 0 || cpu_isset(cpu, p->cpus_allowed)) &&
+	    (p->nr_cpus_allowed > 1))
+		return 1;
+	return 0;
+}
+
+/* Return the second highest RT task, NULL otherwise */
+static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
 {
-	struct rq *rq = arg;
 	struct rt_prio_array *array = &rq->rt.active;
-	struct list_head *head, *curr;
-	struct task_struct *p;
+	struct task_struct *next;
+	struct list_head *queue;
 	int idx;
 
+	if (likely(rq->rt.rt_nr_running < 2))
+		return NULL;
+
 	idx = sched_find_first_bit(array->bitmap);
-	if (idx >= MAX_RT_PRIO)
+	if (unlikely(idx >= MAX_RT_PRIO)) {
+		WARN_ON(1); /* rt_nr_running is bad */
 		return NULL;
+	}
+
+	queue = array->queue + idx;
+	BUG_ON(list_empty(queue));
 
-	head = array->queue + idx;
-	curr = head->prev;
+	next = list_entry(queue->next, struct task_struct, run_list);
+	if (unlikely(pick_rt_task(rq, next, cpu)))
+		goto out;
+
+	if (queue->next->next != queue) {
+		/* same prio task */
+		next = list_entry(queue->next->next, struct task_struct,
+				  run_list);
+		if (pick_rt_task(rq, next, cpu))
+			goto out;
+	}
+
+ retry:
+	/* slower, but more flexible */
+	idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
+	if (unlikely(idx >= MAX_RT_PRIO))
+		return NULL;
 
-	p = list_entry(curr, struct task_struct, run_list);
+	queue = array->queue + idx;
+	BUG_ON(list_empty(queue));
 
-	curr = curr->prev;
+	list_for_each_entry(next, queue, run_list) {
+		if (pick_rt_task(rq, next, cpu))
+			goto out;
+	}
 
-	rq->rt.rt_load_balance_idx = idx;
-	rq->rt.rt_load_balance_head = head;
-	rq->rt.rt_load_balance_curr = curr;
+	goto retry;
 
-	return p;
+ out:
+	return next;
 }
 
-static struct task_struct *load_balance_next_rt(void *arg)
+static DEFINE_PER_CPU(cpumask_t, local_cpu_mask);
+
+static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask)
 {
-	struct rq *rq = arg;
-	struct rt_prio_array *array = &rq->rt.active;
-	struct list_head *head, *curr;
-	struct task_struct *p;
-	int idx;
+	int       lowest_prio = -1;
+	int       lowest_cpu  = -1;
+	int       count       = 0;
+	int       cpu;
 
-	idx = rq->rt.rt_load_balance_idx;
-	head = rq->rt.rt_load_balance_head;
-	curr = rq->rt.rt_load_balance_curr;
+	cpus_and(*lowest_mask, cpu_online_map, task->cpus_allowed);
 
 	/*
-	 * If we arrived back to the head again then
-	 * iterate to the next queue (if any):
+	 * Scan each rq for the lowest prio.
 	 */
-	if (unlikely(head == curr)) {
-		int next_idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
+	for_each_cpu_mask(cpu, *lowest_mask) {
+		struct rq *rq = cpu_rq(cpu);
+
+		/* We look for lowest RT prio or non-rt CPU */
+		if (rq->rt.highest_prio >= MAX_RT_PRIO) {
+			/*
+			 * if we already found a low RT queue
+			 * and now we found this non-rt queue
+			 * clear the mask and set our bit.
+			 * Otherwise just return the queue as is
+			 * and the count==1 will cause the algorithm
+			 * to use the first bit found.
+			 */
+			if (lowest_cpu != -1) {
+				cpus_clear(*lowest_mask);
+				cpu_set(rq->cpu, *lowest_mask);
+			}
+			return 1;
+		}
+
+		/* no locking for now */
+		if ((rq->rt.highest_prio > task->prio)
+		    && (rq->rt.highest_prio >= lowest_prio)) {
+			if (rq->rt.highest_prio > lowest_prio) {
+				/* new low - clear old data */
+				lowest_prio = rq->rt.highest_prio;
+				lowest_cpu = cpu;
+				count = 0;
+			}
+			count++;
+		} else
+			cpu_clear(cpu, *lowest_mask);
+	}
 
-		if (next_idx >= MAX_RT_PRIO)
-			return NULL;
+	/*
+	 * Clear out all the set bits that represent
+	 * runqueues that were of higher prio than
+	 * the lowest_prio.
+	 */
+	if (lowest_cpu > 0) {
+		/*
+		 * Perhaps we could add another cpumask op to
+		 * zero out bits. Like cpu_zero_bits(cpumask, nrbits);
+		 * Then that could be optimized to use memset and such.
+		 */
+		for_each_cpu_mask(cpu, *lowest_mask) {
+			if (cpu >= lowest_cpu)
+				break;
+			cpu_clear(cpu, *lowest_mask);
+		}
+	}
 
-		idx = next_idx;
-		head = array->queue + idx;
-		curr = head->prev;
+	return count;
+}
+
+static inline int pick_optimal_cpu(int this_cpu, cpumask_t *mask)
+{
+	int first;
+
+	/* "this_cpu" is cheaper to preempt than a remote processor */
+	if ((this_cpu != -1) && cpu_isset(this_cpu, *mask))
+		return this_cpu;
+
+	first = first_cpu(*mask);
+	if (first != NR_CPUS)
+		return first;
+
+	return -1;
+}
+
+static int find_lowest_rq(struct task_struct *task)
+{
+	struct sched_domain *sd;
+	cpumask_t *lowest_mask = &__get_cpu_var(local_cpu_mask);
+	int this_cpu = smp_processor_id();
+	int cpu      = task_cpu(task);
+	int count    = find_lowest_cpus(task, lowest_mask);
 
-		rq->rt.rt_load_balance_idx = idx;
-		rq->rt.rt_load_balance_head = head;
+	if (!count)
+		return -1; /* No targets found */
+
+	/*
+	 * There is no sense in performing an optimal search if only one
+	 * target is found.
+	 */
+	if (count == 1)
+		return first_cpu(*lowest_mask);
+
+	/*
+	 * At this point we have built a mask of cpus representing the
+	 * lowest priority tasks in the system.  Now we want to elect
+	 * the best one based on our affinity and topology.
+	 *
+	 * We prioritize the last cpu that the task executed on since
+	 * it is most likely cache-hot in that location.
+	 */
+	if (cpu_isset(cpu, *lowest_mask))
+		return cpu;
+
+	/*
+	 * Otherwise, we consult the sched_domains span maps to figure
+	 * out which cpu is logically closest to our hot cache data.
+	 */
+	if (this_cpu == cpu)
+		this_cpu = -1; /* Skip this_cpu opt if the same */
+
+	for_each_domain(cpu, sd) {
+		if (sd->flags & SD_WAKE_AFFINE) {
+			cpumask_t domain_mask;
+			int       best_cpu;
+
+			cpus_and(domain_mask, sd->span, *lowest_mask);
+
+			best_cpu = pick_optimal_cpu(this_cpu,
+						    &domain_mask);
+			if (best_cpu != -1)
+				return best_cpu;
+		}
+	}
+
+	/*
+	 * And finally, if there were no matches within the domains
+	 * just give the caller *something* to work with from the compatible
+	 * locations.
+	 */
+	return pick_optimal_cpu(this_cpu, lowest_mask);
+}
+
+/* Will lock the rq it finds */
+static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
+{
+	struct rq *lowest_rq = NULL;
+	int tries;
+	int cpu;
+
+	for (tries = 0; tries < RT_MAX_TRIES; tries++) {
+		cpu = find_lowest_rq(task);
+
+		if ((cpu == -1) || (cpu == rq->cpu))
+			break;
+
+		lowest_rq = cpu_rq(cpu);
+
+		/* if the prio of this runqueue changed, try again */
+		if (double_lock_balance(rq, lowest_rq)) {
+			/*
+			 * We had to unlock the run queue. In
+			 * the mean time, task could have
+			 * migrated already or had its affinity changed.
+			 * Also make sure that it wasn't scheduled on its rq.
+			 */
+			if (unlikely(task_rq(task) != rq ||
+				     !cpu_isset(lowest_rq->cpu,
+						task->cpus_allowed) ||
+				     task_running(rq, task) ||
+				     !task->se.on_rq)) {
+
+				spin_unlock(&lowest_rq->lock);
+				lowest_rq = NULL;
+				break;
+			}
+		}
+
+		/* If this rq is still suitable use it. */
+		if (lowest_rq->rt.highest_prio > task->prio)
+			break;
+
+		/* try again */
+		spin_unlock(&lowest_rq->lock);
+		lowest_rq = NULL;
 	}
 
-	p = list_entry(curr, struct task_struct, run_list);
+	return lowest_rq;
+}
 
-	curr = curr->prev;
+/*
+ * If the current CPU has more than one RT task, see if the non
+ * running task can migrate over to a CPU that is running a task
+ * of lesser priority.
+ */
+static int push_rt_task(struct rq *rq)
+{
+	struct task_struct *next_task;
+	struct rq *lowest_rq;
+	int ret = 0;
+	int paranoid = RT_MAX_TRIES;
+
+	if (!rq->rt.overloaded)
+		return 0;
+
+	next_task = pick_next_highest_task_rt(rq, -1);
+	if (!next_task)
+		return 0;
+
+ retry:
+	if (unlikely(next_task == rq->curr)) {
+		WARN_ON(1);
+		return 0;
+	}
 
-	rq->rt.rt_load_balance_curr = curr;
+	/*
+	 * It's possible that the next_task slipped in of
+	 * higher priority than current. If that's the case
+	 * just reschedule current.
+	 */
+	if (unlikely(next_task->prio < rq->curr->prio)) {
+		resched_task(rq->curr);
+		return 0;
+	}
 
-	return p;
+	/* We might release rq lock */
+	get_task_struct(next_task);
+
+	/* find_lock_lowest_rq locks the rq if found */
+	lowest_rq = find_lock_lowest_rq(next_task, rq);
+	if (!lowest_rq) {
+		struct task_struct *task;
+		/*
+		 * find lock_lowest_rq releases rq->lock
+		 * so it is possible that next_task has changed.
+		 * If it has, then try again.
+		 */
+		task = pick_next_highest_task_rt(rq, -1);
+		if (unlikely(task != next_task) && task && paranoid--) {
+			put_task_struct(next_task);
+			next_task = task;
+			goto retry;
+		}
+		goto out;
+	}
+
+	deactivate_task(rq, next_task, 0);
+	set_task_cpu(next_task, lowest_rq->cpu);
+	activate_task(lowest_rq, next_task, 0);
+
+	resched_task(lowest_rq->curr);
+
+	spin_unlock(&lowest_rq->lock);
+
+	ret = 1;
+out:
+	put_task_struct(next_task);
+
+	return ret;
+}
+
+/*
+ * TODO: Currently we just use the second highest prio task on
+ *       the queue, and stop when it can't migrate (or there's
+ *       no more RT tasks).  There may be a case where a lower
+ *       priority RT task has a different affinity than the
+ *       higher RT task. In this case the lower RT task could
+ *       possibly be able to migrate where as the higher priority
+ *       RT task could not.  We currently ignore this issue.
+ *       Enhancements are welcome!
+ */
+static void push_rt_tasks(struct rq *rq)
+{
+	/* push_rt_task will return true if it moved an RT */
+	while (push_rt_task(rq))
+		;
+}
+
+static int pull_rt_task(struct rq *this_rq)
+{
+	int this_cpu = this_rq->cpu, ret = 0, cpu;
+	struct task_struct *p, *next;
+	struct rq *src_rq;
+
+	/*
+	 * If cpusets are used, and we have overlapping
+	 * run queue cpusets, then this algorithm may not catch all.
+	 * This is just the price you pay on trying to keep
+	 * dirtying caches down on large SMP machines.
+	 */
+	if (likely(!rt_overloaded()))
+		return 0;
+
+	next = pick_next_task_rt(this_rq);
+
+	for_each_cpu_mask(cpu, rt_overload_mask) {
+		if (this_cpu == cpu)
+			continue;
+
+		src_rq = cpu_rq(cpu);
+		if (unlikely(src_rq->rt.rt_nr_running <= 1)) {
+			/*
+			 * It is possible that overlapping cpusets
+			 * will miss clearing a non overloaded runqueue.
+			 * Clear it now.
+			 */
+			if (double_lock_balance(this_rq, src_rq)) {
+				/* unlocked our runqueue lock */
+				struct task_struct *old_next = next;
+
+				next = pick_next_task_rt(this_rq);
+				if (next != old_next)
+					ret = 1;
+			}
+			if (likely(src_rq->rt.rt_nr_running <= 1)) {
+				/*
+				 * Small chance that this_rq->curr changed
+				 * but it's really harmless here.
+				 */
+				rt_clear_overload(this_rq);
+			} else {
+				/*
+				 * Heh, the src_rq is now overloaded, since
+				 * we already have the src_rq lock, go straight
+				 * to pulling tasks from it.
+				 */
+				goto try_pulling;
+			}
+			spin_unlock(&src_rq->lock);
+			continue;
+		}
+
+		/*
+		 * We can potentially drop this_rq's lock in
+		 * double_lock_balance, and another CPU could
+		 * steal our next task - hence we must cause
+		 * the caller to recalculate the next task
+		 * in that case:
+		 */
+		if (double_lock_balance(this_rq, src_rq)) {
+			struct task_struct *old_next = next;
+
+			next = pick_next_task_rt(this_rq);
+			if (next != old_next)
+				ret = 1;
+		}
+
+		/*
+		 * Are there still pullable RT tasks?
+		 */
+		if (src_rq->rt.rt_nr_running <= 1) {
+			spin_unlock(&src_rq->lock);
+			continue;
+		}
+
+ try_pulling:
+		p = pick_next_highest_task_rt(src_rq, this_cpu);
+
+		/*
+		 * Do we have an RT task that preempts
+		 * the to-be-scheduled task?
+		 */
+		if (p && (!next || (p->prio < next->prio))) {
+			WARN_ON(p == src_rq->curr);
+			WARN_ON(!p->se.on_rq);
+
+			/*
+			 * There's a chance that p is higher in priority
+			 * than what's currently running on its cpu.
+			 * This is just that p is wakeing up and hasn't
+			 * had a chance to schedule. We only pull
+			 * p if it is lower in priority than the
+			 * current task on the run queue or
+			 * this_rq next task is lower in prio than
+			 * the current task on that rq.
+			 */
+			if (p->prio < src_rq->curr->prio ||
+			    (next && next->prio < src_rq->curr->prio))
+				goto out;
+
+			ret = 1;
+
+			deactivate_task(src_rq, p, 0);
+			set_task_cpu(p, this_cpu);
+			activate_task(this_rq, p, 0);
+			/*
+			 * We continue with the search, just in
+			 * case there's an even higher prio task
+			 * in another runqueue. (low likelyhood
+			 * but possible)
+			 *
+			 * Update next so that we won't pick a task
+			 * on another cpu with a priority lower (or equal)
+			 * than the one we just picked.
+			 */
+			next = p;
+
+		}
+ out:
+		spin_unlock(&src_rq->lock);
+	}
+
+	return ret;
+}
+
+static void schedule_balance_rt(struct rq *rq, struct task_struct *prev)
+{
+	/* Try to pull RT tasks here if we lower this rq's prio */
+	if (unlikely(rt_task(prev)) && rq->rt.highest_prio > prev->prio)
+		pull_rt_task(rq);
+}
+
+static void schedule_tail_balance_rt(struct rq *rq)
+{
+	/*
+	 * If we have more than one rt_task queued, then
+	 * see if we can push the other rt_tasks off to other CPUS.
+	 * Note we may release the rq lock, and since
+	 * the lock was owned by prev, we need to release it
+	 * first via finish_lock_switch and then reaquire it here.
+	 */
+	if (unlikely(rq->rt.overloaded)) {
+		spin_lock_irq(&rq->lock);
+		push_rt_tasks(rq);
+		spin_unlock_irq(&rq->lock);
+	}
+}
+
+
+static void wakeup_balance_rt(struct rq *rq, struct task_struct *p)
+{
+	if (unlikely(rt_task(p)) &&
+	    !task_running(rq, p) &&
+	    (p->prio >= rq->rt.highest_prio) &&
+	    rq->rt.overloaded)
+		push_rt_tasks(rq);
 }
 
 static unsigned long
 load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
-			unsigned long max_nr_move, unsigned long max_load_move,
-			struct sched_domain *sd, enum cpu_idle_type idle,
-			int *all_pinned, int *this_best_prio)
-{
-	int nr_moved;
-	struct rq_iterator rt_rq_iterator;
-	unsigned long load_moved;
-
-	rt_rq_iterator.start = load_balance_start_rt;
-	rt_rq_iterator.next = load_balance_next_rt;
-	/* pass 'busiest' rq argument into
-	 * load_balance_[start|next]_rt iterators
+		unsigned long max_load_move,
+		struct sched_domain *sd, enum cpu_idle_type idle,
+		int *all_pinned, int *this_best_prio)
+{
+	/* don't touch RT tasks */
+	return 0;
+}
+
+static int
+move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
+		 struct sched_domain *sd, enum cpu_idle_type idle)
+{
+	/* don't touch RT tasks */
+	return 0;
+}
+
+static void set_cpus_allowed_rt(struct task_struct *p, cpumask_t *new_mask)
+{
+	int weight = cpus_weight(*new_mask);
+
+	BUG_ON(!rt_task(p));
+
+	/*
+	 * Update the migration status of the RQ if we have an RT task
+	 * which is running AND changing its weight value.
 	 */
-	rt_rq_iterator.arg = busiest;
+	if (p->se.on_rq && (weight != p->nr_cpus_allowed)) {
+		struct rq *rq = task_rq(p);
 
-	nr_moved = balance_tasks(this_rq, this_cpu, busiest, max_nr_move,
-			max_load_move, sd, idle, all_pinned, &load_moved,
-			this_best_prio, &rt_rq_iterator);
+		if ((p->nr_cpus_allowed <= 1) && (weight > 1)) {
+			rq->rt.rt_nr_migratory++;
+		} else if ((p->nr_cpus_allowed > 1) && (weight <= 1)) {
+			BUG_ON(!rq->rt.rt_nr_migratory);
+			rq->rt.rt_nr_migratory--;
+		}
 
-	return load_moved;
+		update_rt_migration(rq);
+	}
+
+	p->cpus_allowed    = *new_mask;
+	p->nr_cpus_allowed = weight;
 }
 
+#else /* CONFIG_SMP */
+# define schedule_tail_balance_rt(rq)	do { } while (0)
+# define schedule_balance_rt(rq, prev)	do { } while (0)
+# define wakeup_balance_rt(rq, p)	do { } while (0)
+#endif /* CONFIG_SMP */
+
 static void task_tick_rt(struct rq *rq, struct task_struct *p)
 {
+	update_curr_rt(rq);
+
 	/*
 	 * RR tasks need a special form of timeslice management.
 	 * FIFO tasks have no timeslices.
@@ -230,13 +823,20 @@ const struct sched_class rt_sched_class = {
 	.enqueue_task		= enqueue_task_rt,
 	.dequeue_task		= dequeue_task_rt,
 	.yield_task		= yield_task_rt,
+#ifdef CONFIG_SMP
+	.select_task_rq		= select_task_rq_rt,
+#endif /* CONFIG_SMP */
 
 	.check_preempt_curr	= check_preempt_curr_rt,
 
 	.pick_next_task		= pick_next_task_rt,
 	.put_prev_task		= put_prev_task_rt,
 
+#ifdef CONFIG_SMP
 	.load_balance		= load_balance_rt,
+	.move_one_task		= move_one_task_rt,
+	.set_cpus_allowed       = set_cpus_allowed_rt,
+#endif
 
 	.set_curr_task          = set_curr_task_rt,
 	.task_tick		= task_tick_rt,