sched: Add a lock break for PREEMPT=y

Since load-balancing can hold rq->locks for quite a long while, allow
breaking out early when there is lock contention.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 4 insertions, 0 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 93fccbadde23..65d08207e925 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -2065,6 +2065,10 @@ static int move_tasks(struct rq *this_rq, int this_cpu, struct rq *busiest,
                  */
                 if (idle == CPU_NEWLY_IDLE && this_rq->nr_running)
                         break;
+
+                if (raw_spin_is_contended(&this_rq->lock) ||
+                                raw_spin_is_contended(&busiest->lock))
+                        break;
 #endif
         } while (load_moved && max_load_move > total_load_moved);