sched: add sched_class->needs_post_schedule() member

We currently run class->post_schedule() outside of the rq->lock, which
means that we need to test for the need to post_schedule outside of
the lock to avoid a forced reacquistion.  This is currently not a problem
as we only look at rq->rt.overloaded.  However, we want to enhance this
going forward to look at more state to reduce the need to post_schedule to
a bare minimum set.  Therefore, we introduce a new member-func called
needs_post_schedule() which tests for the post_schedule condtion without
actually performing the work.  Therefore it is safe to call this
function before the rq->lock is released, because we are guaranteed not
to drop the lock at an intermediate point (such as what post_schedule()
may do).

We will use this later in the series

[ rostedt: removed paranoid BUG_ON ]

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

1 files changed, 1 insertions, 0 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index e5f928a079e8..836a86c32a65 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1012,6 +1012,7 @@ struct sched_class {
                               struct rq *busiest, struct sched_domain *sd,
                               enum cpu_idle_type idle);
         void (*pre_schedule) (struct rq *this_rq, struct task_struct *task);
+        int (*needs_post_schedule) (struct rq *this_rq);
         void (*post_schedule) (struct rq *this_rq);
         void (*task_wake_up) (struct rq *this_rq, struct task_struct *task);