[tip:sched/core] sched: Add a lock break for PREEMPT=y

tip-bot for Peter Zijlstra
2010-01-21T13:53:59Z

Commit-ID: baa8c1102f0cd86e69c1497d61d2ee177e663663
Gitweb: http://git.kernel.org/tip/baa8c1102f0cd86e69c1497d61d2ee177e663663
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Thu, 17 Dec 2009 18:10:09 +0100
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Thu, 21 Jan 2010 13:40:13 +0100

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>
---
kernel/sched_fair.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 93fccba..65d0820 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);