[PATCH] sched: avoid taking rq lock in wake_priority_sleeper

Avoid taking the request queue lock in wake_priority_sleeper if there are no
running processes.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index f04add905bdf..fdd26fffaa20 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2915,6 +2915,9 @@ static inline int wake_priority_sleeper(struct rq *rq)
         int ret = 0;
 
 #ifdef CONFIG_SCHED_SMT
+        if (!rq->nr_running)
+                return 0;
+
         spin_lock(&rq->lock);
         /*
          * If an SMT sibling task has been put to sleep for priority