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, 39 insertions, 0 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 10aa6e1ae3dd..dfa18d55561d 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1280,6 +1280,42 @@ static void task_new_fair(struct rq *rq, struct task_struct *p)
         resched_task(rq->curr);
 }
 
+/*
+ * Priority of the task has changed. Check to see if we preempt
+ * the current task.
+ */
+static void prio_changed_fair(struct rq *rq, struct task_struct *p,
+                              int oldprio, int running)
+{
+        /*
+         * 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);
+}
+
+/*
+ * We switched to the sched_fair class.
+ */
+static void switched_to_fair(struct rq *rq, struct task_struct *p,
+                             int running)
+{
+        /*
+         * We were most likely switched from sched_rt, so
+         * kick off the schedule if running, otherwise just see
+         * if we can still preempt the current task.
+         */
+        if (running)
+                resched_task(rq->curr);
+        else
+                check_preempt_curr(rq, p);
+}
+
 /* Account for a task changing its policy or group.
  *
  * This routine is mostly called to set cfs_rq->curr field when a task
@@ -1318,6 +1354,9 @@ static const struct sched_class fair_sched_class = {
         .set_curr_task          = set_curr_task_fair,
         .task_tick              = task_tick_fair,
         .task_new               = task_new_fair,
+
+        .prio_changed           = prio_changed_fair,
+        .switched_to            = switched_to_fair,
 };
 
 #ifdef CONFIG_SCHED_DEBUG