[PATCH] 2.5.25 remove global semaphore_lock spin lock.

Replace the global semaphore_lock with the spinlock embedded in
the wait_queue_head_t.  None of the data protected by semaphore_lock
is global and there is no need to restrict the system to only allow
one semaphore to be dealt with at a time.

This removes 2 lock round trips from __down() and __down_interruptible().
It also reduces the number of cache lines touched by 1 (the cache line
with seamphore_lock).

1 files changed, 9 insertions, 1 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 49563c9c45d9..c8169afb4b1f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -928,7 +928,7 @@ int default_wake_function(wait_queue_t *curr, unsigned mode, int sync)
  * started to run but is not in state TASK_RUNNING.  try_to_wake_up() returns
  * zero in this (rare) case, and we handle it by continuing to scan the queue.
  */
-static inline void __wake_up_common(wait_queue_head_t *q, unsigned int mode, int nr_exclusive, int sync)
+static void __wake_up_common(wait_queue_head_t *q, unsigned int mode, int nr_exclusive, int sync)
 {
 	struct list_head *tmp, *next;
 
@@ -956,6 +956,14 @@ void __wake_up(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)
 	spin_unlock_irqrestore(&q->lock, flags);
 }
 
+/*
+ * Same as __wake_up but called with the spinlock in wait_queue_head_t held.
+ */
+void __wake_up_locked(wait_queue_head_t *q, unsigned int mode)
+{
+	__wake_up_common(q, mode, 1, 0);
+}
+
 #if CONFIG_SMP
 
 void __wake_up_sync(wait_queue_head_t *q, unsigned int mode, int nr_exclusive)