Index: head/sys/vm/vm_swapout.c
===================================================================
--- head/sys/vm/vm_swapout.c
+++ head/sys/vm/vm_swapout.c
@@ -263,7 +263,7 @@
 	vm_object_t obj, bigobj;
 	int nothingwired;
 
-	if (!vm_map_trylock(map))
+	if (!vm_map_trylock_read(map))
 		return;
 
 	bigobj = NULL;
@@ -327,7 +327,7 @@
 		    vm_map_max(map));
 	}
 
-	vm_map_unlock(map);
+	vm_map_unlock_read(map);
 }
 
 /*