bitbake: bb/event.py: fire_ui_handlers enable threading lock support

In some cases there is a need to fire bb events into multiple
python threads so locking is needed (writing to a fd/socket).

Adding a helper functions for disable/enable by request to avoid
overhead.

[YOCTO #10330]

(Bitbake rev: a583dc0b296415ec904c081c4de96ceef46732a8)

Signed-off-by: Aníbal Limón <anibal.limon@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/event.py

@@ -29,6 +29,8 @@ import logging
 import atexit
 import traceback
 import ast
+import threading
+
 import bb.utils
 import bb.compat
 import bb.exceptions
@@ -68,12 +70,22 @@ _event_handler_map = {}
 _catchall_handlers = {}
 _eventfilter = None
 _uiready = False
+_thread_lock = threading.Lock()
+_thread_lock_enabled = False
 
 if hasattr(__builtins__, '__setitem__'):
     builtins = __builtins__
 else:
     builtins = __builtins__.__dict__
 
+def enable_threadlock():
+    global _thread_lock_enabled
+    _thread_lock_enabled = True
+
+def disable_threadlock():
+    global _thread_lock_enabled
+    _thread_lock_enabled = False
+
 def execute_handler(name, handler, event, d):
     event.data = d
     addedd = False
@@ -146,11 +158,17 @@ def print_ui_queue():
                 logger.handle(event)
 
 def fire_ui_handlers(event, d):
+    global _thread_lock
+    global _thread_lock_enabled
+
     if not _uiready:
         # No UI handlers registered yet, queue up the messages
         ui_queue.append(event)
         return
 
+    if _thread_lock_enabled:
+        _thread_lock.acquire()
+
     errors = []
     for h in _ui_handlers:
         #print "Sending event %s" % event
@@ -169,6 +187,9 @@ def fire_ui_handlers(event, d):
     for h in errors:
         del _ui_handlers[h]
 
+    if _thread_lock_enabled:
+        _thread_lock.release()
+
 def fire(event, d):
     """Fire off an Event"""