sched: use highest_prio.curr for pull threshold

highest_prio.curr is actually a more accurate way to keep track of
the pull_rt_task() threshold since it is always up to date, even
if the "next" task migrates during double_lock.  Therefore, stop
looking at the "next" task object and simply use the highest_prio.curr.

Signed-off-by: Gregory Haskins <ghaskins@novell.com>

1 files changed, 6 insertions, 25 deletions

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index ad36d7232236..f8fb3edadcaa 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -1207,14 +1207,12 @@ static void push_rt_tasks(struct rq *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 task_struct *p;
         struct rq *src_rq;
 
         if (likely(!rt_overloaded(this_rq)))
                 return 0;
 
-        next = pick_next_task_rt(this_rq);
-
         for_each_cpu(cpu, this_rq->rd->rto_mask) {
                 if (this_cpu == cpu)
                         continue;
@@ -1223,17 +1221,9 @@ static int pull_rt_task(struct rq *this_rq)
                 /*
                  * 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:
+                 * alter this_rq
                  */
-                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;
-                }
+                double_lock_balance(this_rq, src_rq);
 
                 /*
                  * Are there still pullable RT tasks?
@@ -1247,7 +1237,7 @@ static int pull_rt_task(struct rq *this_rq)
                  * Do we have an RT task that preempts
                  * the to-be-scheduled task?
                  */
-                if (p && (!next || (p->prio < next->prio))) {
+                if (p && (p->prio < this_rq->rt.highest_prio.curr)) {
                         WARN_ON(p == src_rq->curr);
                         WARN_ON(!p->se.on_rq);
 
@@ -1257,12 +1247,9 @@ static int pull_rt_task(struct rq *this_rq)
                          * 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.
+                         * current task on the run queue
                          */
-                        if (p->prio < src_rq->curr->prio ||
-                            (next && next->prio < src_rq->curr->prio))
+                        if (p->prio < src_rq->curr->prio)
                                 goto skip;
 
                         ret = 1;
@@ -1275,13 +1262,7 @@ static int pull_rt_task(struct rq *this_rq)
                          * 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:
                 double_unlock_balance(this_rq, src_rq);