Provide lock for FileManagers

Author: dschwoerer

xarray/backends/netCDF4_.py

@@ -388,7 +388,7 @@ def __init__(
                         "argument is provided"
                     )
                 root = manager
-            manager = DummyFileManager(root)
+            manager = DummyFileManager(root, lock=NETCDF4_PYTHON_LOCK)
 
         self._manager = manager
         self._group = group
@@ -461,7 +461,7 @@ def open(
         if auto_complex is not None:
             kwargs["auto_complex"] = auto_complex
         manager = CachingFileManager(
-            netCDF4.Dataset, filename, mode=mode, kwargs=kwargs
+            netCDF4.Dataset, filename, lock=lock, mode=mode, kwargs=kwargs
         )
         return cls(manager, group=group, mode=mode, lock=lock, autoclose=autoclose)