sched: RT-balance, add new methods to sched_class

Dmitry Adamushko found that the current implementation of the RT
balancing code left out changes to the sched_setscheduler and
rt_mutex_setprio.

This patch addresses this issue by adding methods to the schedule classes
to handle being switched out of (switched_from) and being switched into
(switched_to) a sched_class. Also a method for changing of priorities
is also added (prio_changed).

This patch also removes some duplicate logic between rt_mutex_setprio and
sched_setscheduler.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 31 insertions, 0 deletions

diff --git a/kernel/sched_idletask.c b/kernel/sched_idletask.c
index ca5374860ae..ef7a2661fa1 100644
--- a/kernel/sched_idletask.c
+++ b/kernel/sched_idletask.c
@@ -69,6 +69,33 @@ static void set_curr_task_idle(struct rq *rq)
 {
 }
 
+static void switched_to_idle(struct rq *rq, struct task_struct *p,
+                             int running)
+{
+        /* Can this actually happen?? */
+        if (running)
+                resched_task(rq->curr);
+        else
+                check_preempt_curr(rq, p);
+}
+
+static void prio_changed_idle(struct rq *rq, struct task_struct *p,
+                              int oldprio, int running)
+{
+        /* This can happen for hot plug CPUS */
+
+        /*
+         * Reschedule if we are currently running on this runqueue and
+         * our priority decreased, or if we are not currently running on
+         * this runqueue and our priority is higher than the current's
+         */
+        if (running) {
+                if (p->prio > oldprio)
+                        resched_task(rq->curr);
+        } else
+                check_preempt_curr(rq, p);
+}
+
 /*
  * Simple, special scheduling class for the per-CPU idle tasks:
  */
@@ -94,5 +121,9 @@ const struct sched_class idle_sched_class = {
 
         .set_curr_task          = set_curr_task_idle,
         .task_tick              = task_tick_idle,
+
+        .prio_changed           = prio_changed_idle,
+        .switched_to            = switched_to_idle,
+
         /* no .task_new for idle tasks */
 };