Cache 'prev' in LITMUS^RT runqueue

LITMUS^RT plugins like to know who 'prev' is. pick_next_task() doesn't
expose that info, so we just cache prev in the runqueue. Could robably
be replaced by looking at 'current' instead.

1 files changed, 8 insertions, 0 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b50b3c2e9887..ad6ba364fc68 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1953,6 +1953,14 @@ static inline void pre_schedule(struct rq *rq, struct task_struct *prev)
 {
         if (prev->sched_class->pre_schedule)
                 prev->sched_class->pre_schedule(rq, prev);
+
+       /* LITMUS^RT not very clean hack: we need to save the prev task as our
+        * scheduling decision rely on it (as we drop the rq lock something in
+        * prev can change...); there is no way to escape this hack apart from
+        * modifying pick_nex_task(rq, _prev_) or falling back on the previous
+        * solution of decoupling scheduling decisions.
+        */
+        rq->litmus.prev = prev;
 }
 
 /* rq->lock is NOT held, but preemption is disabled */