sched: Make set_*_buddy() work on non-task entities

Make set_*_buddy() work on non-task sched_entity, to facilitate the
use of next_buddy to cache a group entity in cases where one of the
tasks within that entity sleeps or gets preempted.

set_skip_buddy() was incorrectly comparing the policy of task that is
yielding to be not equal to SCHED_IDLE. Yielding should happen even
when task yielding is SCHED_IDLE. This change removes the policy check
on the yielding task.

Signed-off-by: Venkatesh Pallipadi <venki@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1302744070-30079-2-git-send-email-venki@google.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/sched_fair.c

@@ -1846,26 +1846,26 @@ wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se)
 
 static void set_last_buddy(struct sched_entity *se)
 {
-	if (likely(task_of(se)->policy != SCHED_IDLE)) {
-		for_each_sched_entity(se)
-			cfs_rq_of(se)->last = se;
-	}
+	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
+		return;
+
+	for_each_sched_entity(se)
+		cfs_rq_of(se)->last = se;
 }
 
 static void set_next_buddy(struct sched_entity *se)
 {
-	if (likely(task_of(se)->policy != SCHED_IDLE)) {
-		for_each_sched_entity(se)
-			cfs_rq_of(se)->next = se;
-	}
+	if (entity_is_task(se) && unlikely(task_of(se)->policy == SCHED_IDLE))
+		return;
+
+	for_each_sched_entity(se)
+		cfs_rq_of(se)->next = se;
 }
 
 static void set_skip_buddy(struct sched_entity *se)
 {
-	if (likely(task_of(se)->policy != SCHED_IDLE)) {
-		for_each_sched_entity(se)
-			cfs_rq_of(se)->skip = se;
-	}
+	for_each_sched_entity(se)
+		cfs_rq_of(se)->skip = se;
 }
 
 /*