X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=kernel%2Fmutex.c;h=632f04c57d82b0207608f10a57f95582833489c1;hb=eed63519e3e74d515d2007ecd895338d0ba2a85c;hp=ff42e975590c3df33e3c4fb66abe7de15162a996;hpb=0d66bf6d3514b35eb6897629059443132992dbd7;p=safe%2Fjmp%2Flinux-2.6

diff --git a/kernel/mutex.c b/kernel/mutex.c
index ff42e97..632f04c 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -89,7 +89,7 @@ __mutex_lock_slowpath(atomic_t *lock_count);
  *
  * This function is similar to (but not equivalent to) down().
  */
-void inline __sched mutex_lock(struct mutex *lock)
+void __sched mutex_lock(struct mutex *lock)
 {
 	might_sleep();
 	/*
@@ -148,7 +148,8 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 
 	preempt_disable();
 	mutex_acquire(&lock->dep_map, subclass, 0, ip);
-#if defined(CONFIG_SMP) && !defined(CONFIG_DEBUG_MUTEXES)
+
+#ifdef CONFIG_MUTEX_SPIN_ON_OWNER
 	/*
 	 * Optimistic spinning.
 	 *
@@ -171,12 +172,6 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 		struct thread_info *owner;
 
 		/*
-		 * If there are pending waiters, join them.
-		 */
-		if (!list_empty(&lock->wait_list))
-			break;
-
-		/*
 		 * If there's an owner, wait for it to either
 		 * release the lock or go to sleep.
 		 */
@@ -184,6 +179,13 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 		if (owner && !mutex_spin_on_owner(lock, owner))
 			break;
 
+		if (atomic_cmpxchg(&lock->count, 1, 0) == 1) {
+			lock_acquired(&lock->dep_map, ip);
+			mutex_set_owner(lock);
+			preempt_enable();
+			return 0;
+		}
+
 		/*
 		 * When there's no owner, we might have preempted between the
 		 * owner acquiring the lock and setting the owner field. If
@@ -193,13 +195,6 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 		if (!owner && (need_resched() || rt_task(task)))
 			break;
 
-		if (atomic_cmpxchg(&lock->count, 1, 0) == 1) {
-			lock_acquired(&lock->dep_map, ip);
-			mutex_set_owner(lock);
-			preempt_enable();
-			return 0;
-		}
-
 		/*
 		 * The cpu_relax() call is a compiler barrier which forces
 		 * everything in this loop to be re-loaded. We don't need
@@ -254,7 +249,9 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 
 		/* didnt get the lock, go to sleep: */
 		spin_unlock_mutex(&lock->wait_lock, flags);
-		__schedule();
+		preempt_enable_no_resched();
+		schedule();
+		preempt_disable();
 		spin_lock_mutex(&lock->wait_lock, flags);
 	}
 
@@ -476,5 +473,28 @@ int __sched mutex_trylock(struct mutex *lock)
 
 	return ret;
 }
-
 EXPORT_SYMBOL(mutex_trylock);
+
+/**
+ * atomic_dec_and_mutex_lock - return holding mutex if we dec to 0
+ * @cnt: the atomic which we are to dec
+ * @lock: the mutex to return holding if we dec to 0
+ *
+ * return true and hold lock if we dec to 0, return false otherwise
+ */
+int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock)
+{
+	/* dec if we can't possibly hit 0 */
+	if (atomic_add_unless(cnt, -1, 1))
+		return 0;
+	/* we might hit 0, so take the lock */
+	mutex_lock(lock);
+	if (!atomic_dec_and_test(cnt)) {
+		/* when we actually did the dec, we didn't hit 0 */
+		mutex_unlock(lock);
+		return 0;
+	}
+	/* we hit 0, and we hold the lock */
+	return 1;
+}
+EXPORT_SYMBOL(atomic_dec_and_mutex_lock);