Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Ingo Molnar:
 "A crash fix and documentation updates"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched: Make sched_class::get_rr_interval() optional
  sched/deadline: Add sched_dl documentation
  sched: Fix docbook parameter annotation error in wait.h

Documentation/scheduler/00-INDEX

@@ -10,5 +10,7 @@ sched-nice-design.txt
 	- How and why the scheduler's nice levels are implemented.
 sched-rt-group.txt
 	- real-time group scheduling.
+sched-deadline.txt
+	- deadline scheduling.
 sched-stats.txt
 	- information on schedstats (Linux Scheduler Statistics).

kernel/sched/core.c

@@ -4347,7 +4347,9 @@ SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
 		goto out_unlock;
 
 	rq = task_rq_lock(p, &flags);
-	time_slice = p->sched_class->get_rr_interval(rq, p);
+	time_slice = 0;
+	if (p->sched_class->get_rr_interval)
+		time_slice = p->sched_class->get_rr_interval(rq, p);
 	task_rq_unlock(rq, p, &flags);
 
 	rcu_read_unlock();

kernel/sched/deadline.c

@@ -351,7 +351,8 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se,
  * disrupting the schedulability of the system. Otherwise, we should
  * refill the runtime and set the deadline a period in the future,
  * because keeping the current (absolute) deadline of the task would
- * result in breaking guarantees promised to other tasks.
+ * result in breaking guarantees promised to other tasks (refer to
+ * Documentation/scheduler/sched-deadline.txt for more informations).
  *
  * This function returns true if:
  *