X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=kernel%2Fmutex.c;h=4c0b7b3e6d2e9a483c6cb4cc384e979911ed03bb;hb=9b8eb4d14767209c83087063352cd04266ecdfd1;hp=fd95eaa672e6ce1e6d1cfd99b73e34eeea0a33d7;hpb=b09d2501ed3d294619cbfbcf828ad39324d0e548;p=safe%2Fjmp%2Flinux-2.6

diff --git a/kernel/mutex.c b/kernel/mutex.c
index fd95eaa..4c0b7b3 100644
--- a/kernel/mutex.c
+++ b/kernel/mutex.c
@@ -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.
 	 *
@@ -171,6 +172,13 @@ __mutex_lock_common(struct mutex *lock, long state, unsigned int subclass,
 		struct thread_info *owner;
 
 		/*
+		 * If we own the BKL, then don't spin. The owner of
+		 * the mutex might be waiting on us to release the BKL.
+		 */
+		if (unlikely(current->lock_depth >= 0))
+			break;
+
+		/*
 		 * If there's an owner, wait for it to either
 		 * release the lock or go to sleep.
 		 */
@@ -248,7 +256,9 @@ __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);
 	}
 
@@ -470,5 +480,28 @@ 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);