[tip:sched/numa] sched: Make sched_class::get_rr_interval() optional

[tip-bot for Peter Zijlstra <tipbot@zytor.com>]

Commit-ID:  a57beec5d427086cdc8d75fd51164577193fa7f4
Gitweb:     http://git.kernel.org/tip/a57beec5d427086cdc8d75fd51164577193fa7f4
Author:     Peter Zijlstra <peterz@infradead.org>
AuthorDate: Mon, 27 Jan 2014 11:54:13 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Tue, 28 Jan 2014 13:08:41 +0100

sched: Make sched_class::get_rr_interval() optional

Not all classes implement (or can implement) a useful get_rr_interval()
function, default to a 0 time-slice for them.

This fixes a crash reported by Tommi Rantala.

Reported-by: Tommi Rantala <tt.rantala@gmail.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Tommi Rantala <tt.rantala@gmail.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140127105413.GC11314@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/core.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 36c951b..81343d6 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4324,7 +4324,9 @@ 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();