rwsem: fix rwsem_is_locked() bugs
[linux-2.6.git] / lib / rwsem-spinlock.c
index 9df3ca5..ccf95bf 100644 (file)
@@ -17,6 +17,19 @@ struct rwsem_waiter {
 #define RWSEM_WAITING_FOR_WRITE        0x00000002
 };
 
+int rwsem_is_locked(struct rw_semaphore *sem)
+{
+       int ret = 1;
+       unsigned long flags;
+
+       if (spin_trylock_irqsave(&sem->wait_lock, flags)) {
+               ret = (sem->activity != 0);
+               spin_unlock_irqrestore(&sem->wait_lock, flags);
+       }
+       return ret;
+}
+EXPORT_SYMBOL(rwsem_is_locked);
+
 /*
  * initialise the semaphore
  */
@@ -34,6 +47,7 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
        spin_lock_init(&sem->wait_lock);
        INIT_LIST_HEAD(&sem->wait_list);
 }
+EXPORT_SYMBOL(__init_rwsem);
 
 /*
  * handle the lock release when processes blocked on it that can now run
@@ -305,12 +319,3 @@ void __downgrade_write(struct rw_semaphore *sem)
        spin_unlock_irqrestore(&sem->wait_lock, flags);
 }
 
-EXPORT_SYMBOL(__init_rwsem);
-EXPORT_SYMBOL(__down_read);
-EXPORT_SYMBOL(__down_read_trylock);
-EXPORT_SYMBOL(__down_write_nested);
-EXPORT_SYMBOL(__down_write);
-EXPORT_SYMBOL(__down_write_trylock);
-EXPORT_SYMBOL(__up_read);
-EXPORT_SYMBOL(__up_write);
-EXPORT_SYMBOL(__downgrade_write);