[PATCH 6/6] sched: Add a lock break for PREEMPT=y

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

[-- Attachment #1: sched-lb-6.patch --]
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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>
---
 kernel/sched_fair.c |    4 ++++
 1 file changed, 4 insertions(+)

Index: linux-2.6/kernel/sched_fair.c
===================================================================
--- linux-2.6.orig/kernel/sched_fair.c
+++ linux-2.6/kernel/sched_fair.c
@@ -2065,6 +2065,10 @@ static int move_tasks(struct rq *this_rq
 		 */
 		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);
 

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