+EXPORT_SYMBOL(_raw_write_lock);
+
+int _raw_write_trylock(rwlock_t *rw)
+{
+ if (test_and_set_bit(31, &(rw)->lock)) /* someone has a write lock */
+ return 0;
+
+ if ((rw)->lock & ~(1<<31)) { /* someone has a read lock */
+ /* clear our write lock and wait for reads to go away */
+ clear_bit(31,&(rw)->lock);
+ return 0;
+ }
+ wmb();
+ return 1;
+}
+EXPORT_SYMBOL(_raw_write_trylock);