2.6.24-git2

 kernel

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 9ba3daa..274b40d 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -3,6 +3,217 @@
  * policies)
  */
 
+#ifdef CONFIG_SMP
+
+static inline int rt_overloaded(struct rq *rq)
+{
+   return atomic_read(&rq->rd->rto_count);
+}
+
+static inline void rt_set_overload(struct rq *rq)
+{
+   cpu_set(rq->cpu, rq->rd->rto_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(&rq->rd->rto_count);
+}
+
+static inline void rt_clear_overload(struct rq *rq)
+{
+   /* the order here really doesn't matter */
+   atomic_dec(&rq->rd->rto_count);
+   cpu_clear(rq->cpu, rq->rd->rto_mask);
+}
+
+static void update_rt_migration(struct rq *rq)
+{
+   if (rq->rt.rt_nr_migratory && (rq->rt.rt_nr_running > 1)) {
+      if (!rq->rt.overloaded) {
+         rt_set_overload(rq);
+         rq->rt.overloaded = 1;
+      }
+   } else if (rq->rt.overloaded) {
+      rt_clear_overload(rq);
+      rq->rt.overloaded = 0;
+   }
+}
+#endif /* CONFIG_SMP */
+
+static inline struct task_struct *rt_task_of(struct sched_rt_entity *rt_se)
+{
+   return container_of(rt_se, struct task_struct, rt);
+}
+
+static inline int on_rt_rq(struct sched_rt_entity *rt_se)
+{
+   return !list_empty(&rt_se->run_list);
+}
+
+#ifdef CONFIG_FAIR_GROUP_SCHED
+
+static inline unsigned int sched_rt_ratio(struct rt_rq *rt_rq)
+{
+   if (!rt_rq->tg)
+      return SCHED_RT_FRAC;
+
+   return rt_rq->tg->rt_ratio;
+}
+
+#define for_each_leaf_rt_rq(rt_rq, rq) \
+   list_for_each_entry(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
+
+static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
+{
+   return rt_rq->rq;
+}
+
+static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
+{
+   return rt_se->rt_rq;
+}
+
+#define for_each_sched_rt_entity(rt_se) \
+   for (; rt_se; rt_se = rt_se->parent)
+
+static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
+{
+   return rt_se->my_q;
+}
+
+static void enqueue_rt_entity(struct sched_rt_entity *rt_se);
+static void dequeue_rt_entity(struct sched_rt_entity *rt_se);
+
+static void sched_rt_ratio_enqueue(struct rt_rq *rt_rq)
+{
+   struct sched_rt_entity *rt_se = rt_rq->rt_se;
+
+   if (rt_se && !on_rt_rq(rt_se) && rt_rq->rt_nr_running) {
+      struct task_struct *curr = rq_of_rt_rq(rt_rq)->curr;
+
+      enqueue_rt_entity(rt_se);
+      if (rt_rq->highest_prio < curr->prio)
+         resched_task(curr);
+   }
+}
+
+static void sched_rt_ratio_dequeue(struct rt_rq *rt_rq)
+{
+   struct sched_rt_entity *rt_se = rt_rq->rt_se;
+
+   if (rt_se && on_rt_rq(rt_se))
+      dequeue_rt_entity(rt_se);
+}
+
+#else
+
+static inline unsigned int sched_rt_ratio(struct rt_rq *rt_rq)
+{
+   return sysctl_sched_rt_ratio;
+}
+
+#define for_each_leaf_rt_rq(rt_rq, rq) \
+   for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
+
+static inline struct rq *rq_of_rt_rq(struct rt_rq *rt_rq)
+{
+   return container_of(rt_rq, struct rq, rt);
+}
+
+static inline struct rt_rq *rt_rq_of_se(struct sched_rt_entity *rt_se)
+{
+   struct task_struct *p = rt_task_of(rt_se);
+   struct rq *rq = task_rq(p);
+
+   return &rq->rt;
+}
+
+#define for_each_sched_rt_entity(rt_se) \
+   for (; rt_se; rt_se = NULL)
+
+static inline struct rt_rq *group_rt_rq(struct sched_rt_entity *rt_se)
+{
+   return NULL;
+}
+
+static inline void sched_rt_ratio_enqueue(struct rt_rq *rt_rq)
+{
+}
+
+static inline void sched_rt_ratio_dequeue(struct rt_rq *rt_rq)
+{
+}
+
+#endif
+
+static inline int rt_se_prio(struct sched_rt_entity *rt_se)
+{
+#ifdef CONFIG_FAIR_GROUP_SCHED
+   struct rt_rq *rt_rq = group_rt_rq(rt_se);
+
+   if (rt_rq)
+      return rt_rq->highest_prio;
+#endif
+
+   return rt_task_of(rt_se)->prio;
+}
+
+static int sched_rt_ratio_exceeded(struct rt_rq *rt_rq)
+{
+   unsigned int rt_ratio = sched_rt_ratio(rt_rq);
+   u64 period, ratio;
+
+   if (rt_ratio == SCHED_RT_FRAC)
+      return 0;
+
+   if (rt_rq->rt_throttled)
+      return 1;
+
+   period = (u64)sysctl_sched_rt_period * NSEC_PER_MSEC;
+   ratio = (period * rt_ratio) >> SCHED_RT_FRAC_SHIFT;
+
+   if (rt_rq->rt_time > ratio) {
+      struct rq *rq = rq_of_rt_rq(rt_rq);
+
+      rq->rt_throttled = 1;
+      rt_rq->rt_throttled = 1;
+
+      sched_rt_ratio_dequeue(rt_rq);
+      return 1;
+   }
+
+   return 0;
+}
+
+static void update_sched_rt_period(struct rq *rq)
+{
+   struct rt_rq *rt_rq;
+   u64 period;
+
+   while (rq->clock > rq->rt_period_expire) {
+      period = (u64)sysctl_sched_rt_period * NSEC_PER_MSEC;
+      rq->rt_period_expire += period;
+
+      for_each_leaf_rt_rq(rt_rq, rq) {
+         unsigned long rt_ratio = sched_rt_ratio(rt_rq);
+         u64 ratio = (period * rt_ratio) >> SCHED_RT_FRAC_SHIFT;
+
+         rt_rq->rt_time -= min(rt_rq->rt_time, ratio);
+         if (rt_rq->rt_throttled) {
+            rt_rq->rt_throttled = 0;
+            sched_rt_ratio_enqueue(rt_rq);
+         }
+      }
+
+      rq->rt_throttled = 0;
+   }
+}
+
 /*
  * Update the current task's runtime statistics. Skip current tasks that
  * are not in our scheduling class.
@@ -10,6 +221,8 @@
 static void update_curr_rt(struct rq *rq)
 {
    struct task_struct *curr = rq->curr;
+   struct sched_rt_entity *rt_se = &curr->rt;
+   struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
    u64 delta_exec;
 
    if (!task_has_rt_policy(curr))
@@ -24,47 +237,228 @@ 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);
+
+   rt_rq->rt_time += delta_exec;
+   /*
+    * might make it a tad more accurate:
+    *
+    * update_sched_rt_period(rq);
+    */
+   if (sched_rt_ratio_exceeded(rt_rq))
+      resched_task(curr);
 }
 
-static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
+static inline
+void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
+{
+   WARN_ON(!rt_prio(rt_se_prio(rt_se)));
+   rt_rq->rt_nr_running++;
+#if defined CONFIG_SMP || defined CONFIG_FAIR_GROUP_SCHED
+   if (rt_se_prio(rt_se) < rt_rq->highest_prio)
+      rt_rq->highest_prio = rt_se_prio(rt_se);
+#endif
+#ifdef CONFIG_SMP
+   if (rt_se->nr_cpus_allowed > 1) {
+      struct rq *rq = rq_of_rt_rq(rt_rq);
+      rq->rt.rt_nr_migratory++;
+   }
+
+   update_rt_migration(rq_of_rt_rq(rt_rq));
+#endif
+}
+
+static inline
+void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq)
+{
+   WARN_ON(!rt_prio(rt_se_prio(rt_se)));
+   WARN_ON(!rt_rq->rt_nr_running);
+   rt_rq->rt_nr_running--;
+#if defined CONFIG_SMP || defined CONFIG_FAIR_GROUP_SCHED
+   if (rt_rq->rt_nr_running) {
+      struct rt_prio_array *array;
+
+      WARN_ON(rt_se_prio(rt_se) < rt_rq->highest_prio);
+      if (rt_se_prio(rt_se) == rt_rq->highest_prio) {
+         /* recalculate */
+         array = &rt_rq->active;
+         rt_rq->highest_prio =
+            sched_find_first_bit(array->bitmap);
+      } /* otherwise leave rq->highest prio alone */
+   } else
+      rt_rq->highest_prio = MAX_RT_PRIO;
+#endif
+#ifdef CONFIG_SMP
+   if (rt_se->nr_cpus_allowed > 1) {
+      struct rq *rq = rq_of_rt_rq(rt_rq);
+      rq->rt.rt_nr_migratory--;
+   }
+
+   update_rt_migration(rq_of_rt_rq(rt_rq));
+#endif /* CONFIG_SMP */
+}
+
+static void enqueue_rt_entity(struct sched_rt_entity *rt_se)
+{
+   struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
+   struct rt_prio_array *array = &rt_rq->active;
+   struct rt_rq *group_rq = group_rt_rq(rt_se);
+
+   if (group_rq && group_rq->rt_throttled)
+      return;
+
+   list_add_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se));
+   __set_bit(rt_se_prio(rt_se), array->bitmap);
+
+   inc_rt_tasks(rt_se, rt_rq);
+}
+
+static void dequeue_rt_entity(struct sched_rt_entity *rt_se)
 {
-   struct rt_prio_array *array = &rq->rt.active;
+   struct rt_rq *rt_rq = rt_rq_of_se(rt_se);
+   struct rt_prio_array *array = &rt_rq->active;
+
+   list_del_init(&rt_se->run_list);
+   if (list_empty(array->queue + rt_se_prio(rt_se)))
+      __clear_bit(rt_se_prio(rt_se), array->bitmap);
 
-   list_add_tail(&p->run_list, array->queue + p->prio);
-   __set_bit(p->prio, array->bitmap);
+   dec_rt_tasks(rt_se, rt_rq);
+}
+
+/*
+ * 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.
+ *      doesn't matter much for now, as h=2 for GROUP_SCHED.
+ */
+static void dequeue_rt_stack(struct task_struct *p)
+{
+   struct sched_rt_entity *rt_se, *top_se;
+
+   /*
+    * 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);
 }
 
 /*
  * Adding/removing a task to/from a priority array:
  */
+static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
+{
+   struct sched_rt_entity *rt_se = &p->rt;
+
+   if (wakeup)
+      rt_se->timeout = 0;
+
+   dequeue_rt_stack(p);
+
+   /*
+    * enqueue everybody, bottom - up.
+    */
+   for_each_sched_rt_entity(rt_se)
+      enqueue_rt_entity(rt_se);
+
+   inc_cpu_load(rq, p->se.load.weight);
+}
+
 static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
 {
-   struct rt_prio_array *array = &rq->rt.active;
+   struct sched_rt_entity *rt_se = &p->rt;
+   struct rt_rq *rt_rq;
 
    update_curr_rt(rq);
 
-   list_del(&p->run_list);
-   if (list_empty(array->queue + p->prio))
-      __clear_bit(p->prio, array->bitmap);
+   dequeue_rt_stack(p);
+
+   /*
+    * re-enqueue all non-empty rt_rq entities.
+    */
+   for_each_sched_rt_entity(rt_se) {
+      rt_rq = group_rt_rq(rt_se);
+      if (rt_rq && rt_rq->rt_nr_running)
+         enqueue_rt_entity(rt_se);
+   }
+
+   dec_cpu_load(rq, p->se.load.weight);
 }
 
 /*
  * Put task to the end of the run list without the overhead of dequeue
  * followed by enqueue.
  */
+static
+void requeue_rt_entity(struct rt_rq *rt_rq, struct sched_rt_entity *rt_se)
+{
+   struct rt_prio_array *array = &rt_rq->active;
+
+   list_move_tail(&rt_se->run_list, array->queue + rt_se_prio(rt_se));
+}
+
 static void requeue_task_rt(struct rq *rq, struct task_struct *p)
 {
-   struct rt_prio_array *array = &rq->rt.active;
+   struct sched_rt_entity *rt_se = &p->rt;
+   struct rt_rq *rt_rq;
 
-   list_move_tail(&p->run_list, array->queue + p->prio);
+   for_each_sched_rt_entity(rt_se) {
+      rt_rq = rt_rq_of_se(rt_se);
+      requeue_rt_entity(rt_rq, rt_se);
+   }
 }
 
-static void
-yield_task_rt(struct rq *rq)
+static void 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->rt.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:
  */
@@ -74,25 +468,48 @@ static void check_preempt_curr_rt(struct rq *rq, struct task_struct *p)
       resched_task(rq->curr);
 }
 
-static struct task_struct *pick_next_task_rt(struct rq *rq)
+static struct sched_rt_entity *pick_next_rt_entity(struct rq *rq,
+                     struct rt_rq *rt_rq)
 {
-   struct rt_prio_array *array = &rq->rt.active;
-   struct task_struct *next;
+   struct rt_prio_array *array = &rt_rq->active;
+   struct sched_rt_entity *next = NULL;
    struct list_head *queue;
    int idx;
 
    idx = sched_find_first_bit(array->bitmap);
-   if (idx >= MAX_RT_PRIO)
-      return NULL;
+   BUG_ON(idx >= MAX_RT_PRIO);
 
    queue = array->queue + idx;
-   next = list_entry(queue->next, struct task_struct, run_list);
-
-   next->se.exec_start = rq->clock;
+   next = list_entry(queue->next, struct sched_rt_entity, run_list);
 
    return next;
 }
 
+static struct task_struct *pick_next_task_rt(struct rq *rq)
+{
+   struct sched_rt_entity *rt_se;
+   struct task_struct *p;
+   struct rt_rq *rt_rq;
+
+   rt_rq = &rq->rt;
+
+   if (unlikely(!rt_rq->rt_nr_running))
+      return NULL;
+
+   if (sched_rt_ratio_exceeded(rt_rq))
+      return NULL;
+
+   do {
+      rt_se = pick_next_rt_entity(rq, rt_rq);
+      BUG_ON(!rt_se);
+      rt_rq = group_rt_rq(rt_se);
+   } while (rt_rq);
+
+   p = rt_task_of(rt_se);
+   p->se.exec_start = rq->clock;
+   return p;
+}
+
 static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
 {
    update_curr_rt(rq);
@@ -100,76 +517,448 @@ static void put_prev_task_rt(struct rq *rq, struct task_struct *p)
 }
 
 #ifdef CONFIG_SMP
-/*
- * 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)
+
+/* 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)
 {
-   struct rq *rq = arg;
-   struct rt_prio_array *array = &rq->rt.active;
-   struct list_head *head, *curr;
-   struct task_struct *p;
+   if (!task_running(rq, p) &&
+       (cpu < 0 || cpu_isset(cpu, p->cpus_allowed)) &&
+       (p->rt.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 task_struct *next = NULL;
+   struct sched_rt_entity *rt_se;
+   struct rt_prio_array *array;
+   struct rt_rq *rt_rq;
    int idx;
 
-   idx = sched_find_first_bit(array->bitmap);
-   if (idx >= MAX_RT_PRIO)
-      return NULL;
+   for_each_leaf_rt_rq(rt_rq, rq) {
+      array = &rt_rq->active;
+      idx = sched_find_first_bit(array->bitmap);
+ next_idx:
+      if (idx >= MAX_RT_PRIO)
+         continue;
+      if (next && next->prio < idx)
+         continue;
+      list_for_each_entry(rt_se, array->queue + idx, run_list) {
+         struct task_struct *p = rt_task_of(rt_se);
+         if (pick_rt_task(rq, p, cpu)) {
+            next = p;
+            break;
+         }
+      }
+      if (!next) {
+         idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
+         goto next_idx;
+      }
+   }
 
-   head = array->queue + idx;
-   curr = head->prev;
+   return next;
+}
 
-   p = list_entry(curr, struct task_struct, run_list);
+static DEFINE_PER_CPU(cpumask_t, local_cpu_mask);
 
-   curr = curr->prev;
+static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask)
+{
+   int       lowest_prio = -1;
+   int       lowest_cpu  = -1;
+   int       count       = 0;
+   int       cpu;
 
-   rq->rt.rt_load_balance_idx = idx;
-   rq->rt.rt_load_balance_head = head;
-   rq->rt.rt_load_balance_curr = curr;
+   cpus_and(*lowest_mask, task_rq(task)->rd->online, task->cpus_allowed);
 
-   return p;
+   /*
+    * Scan each rq for the lowest prio.
+    */
+   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);
+   }
+
+   /*
+    * 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);
+      }
+   }
+
+   return count;
 }
 
-static struct task_struct *load_balance_next_rt(void *arg)
+static inline int pick_optimal_cpu(int this_cpu, cpumask_t *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 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);
 
-   idx = rq->rt.rt_load_balance_idx;
-   head = rq->rt.rt_load_balance_head;
-   curr = rq->rt.rt_load_balance_curr;
+   if (!count)
+      return -1; /* No targets found */
 
    /*
-    * If we arrived back to the head again then
-    * iterate to the next queue (if any):
+    * There is no sense in performing an optimal search if only one
+    * target is found.
     */
-   if (unlikely(head == curr)) {
-      int next_idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
+   if (count == 1)
+      return first_cpu(*lowest_mask);
 
-      if (next_idx >= MAX_RT_PRIO)
-         return NULL;
+   /*
+    * 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;
 
-      idx = next_idx;
-      head = array->queue + idx;
-      curr = head->prev;
+         cpus_and(domain_mask, sd->span, *lowest_mask);
 
-      rq->rt.rt_load_balance_idx = idx;
-      rq->rt.rt_load_balance_head = head;
+         best_cpu = pick_optimal_cpu(this_cpu,
+                      &domain_mask);
+         if (best_cpu != -1)
+            return best_cpu;
+      }
    }
 
-   p = list_entry(curr, struct task_struct, run_list);
+   /*
+    * 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);
+}
 
-   curr = curr->prev;
+/* 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;
 
-   rq->rt.rt_load_balance_curr = curr;
+   for (tries = 0; tries < RT_MAX_TRIES; tries++) {
+      cpu = find_lowest_rq(task);
 
-   return p;
+      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;
+   }
+
+   return lowest_rq;
+}
+
+/*
+ * 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;
+   }
+
+   /*
+    * 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;
+   }
+
+   /* 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 (likely(!rt_overloaded(this_rq)))
+      return 0;
+
+   next = pick_next_task_rt(this_rq);
+
+   for_each_cpu_mask(cpu, this_rq->rd->rto_mask) {
+      if (this_cpu == cpu)
+         continue;
+
+      src_rq = cpu_rq(cpu);
+      /*
+       * 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)
+         goto skip;
+
+      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 skip;
+
+         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;
+
+      }
+ skip:
+      spin_unlock(&src_rq->lock);
+   }
+
+   return ret;
+}
+
+static void pre_schedule_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 post_schedule_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 task_wake_up_rt(struct rq *rq, struct task_struct *p)
+{
+   if (!task_running(rq, p) &&
+       (p->prio >= rq->rt.highest_prio) &&
+       rq->rt.overloaded)
+      push_rt_tasks(rq);
 }
 
 static unsigned long
@@ -178,38 +967,170 @@ load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
       struct sched_domain *sd, enum cpu_idle_type idle,
       int *all_pinned, int *this_best_prio)
 {
-   struct rq_iterator rt_rq_iterator;
-
-   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
-    */
-   rt_rq_iterator.arg = busiest;
-
-   return balance_tasks(this_rq, this_cpu, busiest, max_load_move, sd,
-              idle, all_pinned, this_best_prio, &rt_rq_iterator);
+   /* 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)
 {
-   struct rq_iterator rt_rq_iterator;
+   /* 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));
 
-   rt_rq_iterator.start = load_balance_start_rt;
-   rt_rq_iterator.next = load_balance_next_rt;
-   rt_rq_iterator.arg = busiest;
+   /*
+    * Update the migration status of the RQ if we have an RT task
+    * which is running AND changing its weight value.
+    */
+   if (p->se.on_rq && (weight != p->rt.nr_cpus_allowed)) {
+      struct rq *rq = task_rq(p);
+
+      if ((p->rt.nr_cpus_allowed <= 1) && (weight > 1)) {
+         rq->rt.rt_nr_migratory++;
+      } else if ((p->rt.nr_cpus_allowed > 1) && (weight <= 1)) {
+         BUG_ON(!rq->rt.rt_nr_migratory);
+         rq->rt.rt_nr_migratory--;
+      }
+
+      update_rt_migration(rq);
+   }
 
-   return iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
-              &rt_rq_iterator);
+   p->cpus_allowed    = *new_mask;
+   p->rt.nr_cpus_allowed = weight;
 }
-#endif
 
-static void task_tick_rt(struct rq *rq, struct task_struct *p)
+/* Assumes rq->lock is held */
+static void join_domain_rt(struct rq *rq)
+{
+   if (rq->rt.overloaded)
+      rt_set_overload(rq);
+}
+
+/* Assumes rq->lock is held */
+static void leave_domain_rt(struct rq *rq)
+{
+   if (rq->rt.overloaded)
+      rt_clear_overload(rq);
+}
+
+/*
+ * When switch from the rt queue, we bring ourselves to a position
+ * that we might want to pull RT tasks from other runqueues.
+ */
+static void switched_from_rt(struct rq *rq, struct task_struct *p,
+            int running)
+{
+   /*
+    * If there are other RT tasks then we will reschedule
+    * and the scheduling of the other RT tasks will handle
+    * the balancing. But if we are the last RT task
+    * we may need to handle the pulling of RT tasks
+    * now.
+    */
+   if (!rq->rt.rt_nr_running)
+      pull_rt_task(rq);
+}
+#endif /* CONFIG_SMP */
+
+/*
+ * When switching a task to RT, we may overload the runqueue
+ * with RT tasks. In this case we try to push them off to
+ * other runqueues.
+ */
+static void switched_to_rt(struct rq *rq, struct task_struct *p,
+            int running)
+{
+   int check_resched = 1;
+
+   /*
+    * If we are already running, then there's nothing
+    * that needs to be done. But if we are not running
+    * we may need to preempt the current running task.
+    * If that current running task is also an RT task
+    * then see if we can move to another run queue.
+    */
+   if (!running) {
+#ifdef CONFIG_SMP
+      if (rq->rt.overloaded && push_rt_task(rq) &&
+          /* Don't resched if we changed runqueues */
+          rq != task_rq(p))
+         check_resched = 0;
+#endif /* CONFIG_SMP */
+      if (check_resched && p->prio < rq->curr->prio)
+         resched_task(rq->curr);
+   }
+}
+
+/*
+ * Priority of the task has changed. This may cause
+ * us to initiate a push or pull.
+ */
+static void prio_changed_rt(struct rq *rq, struct task_struct *p,
+             int oldprio, int running)
+{
+   if (running) {
+#ifdef CONFIG_SMP
+      /*
+       * If our priority decreases while running, we
+       * may need to pull tasks to this runqueue.
+       */
+      if (oldprio < p->prio)
+         pull_rt_task(rq);
+      /*
+       * If there's a higher priority task waiting to run
+       * then reschedule.
+       */
+      if (p->prio > rq->rt.highest_prio)
+         resched_task(p);
+#else
+      /* For UP simply resched on drop of prio */
+      if (oldprio < p->prio)
+         resched_task(p);
+#endif /* CONFIG_SMP */
+   } else {
+      /*
+       * This task is not running, but if it is
+       * greater than the current running task
+       * then reschedule.
+       */
+      if (p->prio < rq->curr->prio)
+         resched_task(rq->curr);
+   }
+}
+
+static void watchdog(struct rq *rq, struct task_struct *p)
+{
+   unsigned long soft, hard;
+
+   if (!p->signal)
+      return;
+
+   soft = p->signal->rlim[RLIMIT_RTTIME].rlim_cur;
+   hard = p->signal->rlim[RLIMIT_RTTIME].rlim_max;
+
+   if (soft != RLIM_INFINITY) {
+      unsigned long next;
+
+      p->rt.timeout++;
+      next = DIV_ROUND_UP(min(soft, hard), USEC_PER_SEC/HZ);
+      if (p->rt.timeout > next)
+         p->it_sched_expires = p->se.sum_exec_runtime;
+   }
+}
+
+static void task_tick_rt(struct rq *rq, struct task_struct *p, int queued)
 {
    update_curr_rt(rq);
 
+   watchdog(rq, p);
+
    /*
     * RR tasks need a special form of timeslice management.
     * FIFO tasks have no timeslices.
@@ -217,16 +1138,16 @@ static void task_tick_rt(struct rq *rq, struct task_struct *p)
    if (p->policy != SCHED_RR)
       return;
 
-   if (--p->time_slice)
+   if (--p->rt.time_slice)
       return;
 
-   p->time_slice = DEF_TIMESLICE;
+   p->rt.time_slice = DEF_TIMESLICE;
 
    /*
     * Requeue to the end of queue if we are not the only element
     * on the queue:
     */
-   if (p->run_list.prev != p->run_list.next) {
+   if (p->rt.run_list.prev != p->rt.run_list.next) {
       requeue_task_rt(rq, p);
       set_tsk_need_resched(p);
    }
@@ -244,6 +1165,9 @@ 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,
 
@@ -253,8 +1177,18 @@ const struct sched_class rt_sched_class = {
 #ifdef CONFIG_SMP
    .load_balance      = load_balance_rt,
    .move_one_task      = move_one_task_rt,
+   .set_cpus_allowed       = set_cpus_allowed_rt,
+   .join_domain            = join_domain_rt,
+   .leave_domain           = leave_domain_rt,
+   .pre_schedule      = pre_schedule_rt,
+   .post_schedule      = post_schedule_rt,
+   .task_wake_up      = task_wake_up_rt,
+   .switched_from      = switched_from_rt,
 #endif
 
    .set_curr_task          = set_curr_task_rt,
    .task_tick      = task_tick_rt,
+
+   .prio_changed      = prio_changed_rt,
+   .switched_to      = switched_to_rt,
 };