bitbake: cooker/cookerdata/event: Improve class handlers management

Similarly to the execution context changes, establish better lifetime
management API of the class event handlers.

(Bitbake rev: 54e35a6cceead9521f8b1dacd48e55064e85c8bd)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/cooker.py

@@ -1455,7 +1455,7 @@ class Parser(multiprocessing.Process):
         self.init = init
         multiprocessing.Process.__init__(self)
         self.context = bb.utils.get_context().copy()
-        self.handlers = bb.event._handlers.copy()
+        self.handlers = bb.event.get_class_handlers().copy()
 
     def run(self):
         if self.init:
@@ -1492,7 +1492,7 @@ class Parser(multiprocessing.Process):
         try:
             # Reset our environment and handlers to the original settings
             bb.utils.set_context(self.context.copy())
-            bb.event._handlers = self.handlers.copy()
+            bb.event.set_class_handlers(self.handlers.copy())
             return True, bb.cache.Cache.parse(filename, appends, self.cfg, caches_array)
         except Exception as exc:
             tb = sys.exc_info()[2]

bitbake/lib/bb/cookerdata.py

@@ -174,6 +174,7 @@ class CookerDataBuilder(object):
         self.tracking = params.tracking
 
         bb.utils.set_context(bb.utils.clean_context())
+        bb.event.set_class_handlers(bb.event.clean_class_handlers())
         self.data = bb.data.init()
         if self.tracking:
             self.data.enableTracking()

bitbake/lib/bb/event.py

@@ -50,8 +50,17 @@ class Event(object):
 Registered        = 10
 AlreadyRegistered = 14
 
+def get_class_handlers():
+    return _handlers
+
+def set_class_handlers(h):
+    _handlers = h
+
+def clean_class_handlers():
+    return bb.compat.OrderedDict()
+
 # Internal
-_handlers = bb.compat.OrderedDict()
+_handlers = clean_class_handlers()
 _ui_handlers = {}
 _ui_handler_seq = 0