sched: Give CPU bound RT tasks preference

From:: Steven Rostedt <srostedt@redhat.com>

Commit: b3bc211cfe7d5fe94b310480d78e00bea96fbf2a upstream

If a high priority task is waking up on a CPU that is running a
lower priority task that is bound to a CPU, see if we can move the
high RT task to another CPU first. Note, if all other CPUs are
running higher priority tasks than the CPU bounded current task,
then it will be preempted regardless.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Cc: Gregory Haskins <ghaskins@novell.com>
LKML-Reference: <20100921024138.888922071@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 86a2f77977c61564e5a73880271c7e77d13442fd..25bd3a3ca0cced7e8b2a7e3cb0f402f6cd5fcfee 100644 (file)
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -971,7 +971,8 @@ select_task_rq_rt(struct rq *rq, struct task_struct *p, int sd_flag, int flags)
         * For equal prio tasks, we just let the scheduler sort it out.
         */
        if (unlikely(rt_task(rq->curr)) &&
-           rq->curr->prio < p->prio &&
+           (rq->curr->rt.nr_cpus_allowed < 2 ||
+            rq->curr->prio < p->prio) &&
            (p->rt.nr_cpus_allowed > 1)) {
                int cpu = find_lowest_rq(p);
 
@@ -1491,9 +1492,10 @@ static void task_woken_rt(struct rq *rq, struct task_struct *p)
        if (!task_running(rq, p) &&
            !test_tsk_need_resched(rq->curr) &&
            has_pushable_tasks(rq) &&
+           p->rt.nr_cpus_allowed > 1 &&
            rt_task(rq->curr) &&
-           rq->curr->prio < p->prio &&
-           p->rt.nr_cpus_allowed > 1)
+           (rq->curr->rt.nr_cpus_allowed < 2 ||
+            rq->curr->prio < p->prio))
                push_rt_tasks(rq);
 }