Add PollScheduler.terminate() for interruption.

This allows PollScheduler instances to do basic cleanup and terminate
gracefully when SIGINT or SIGTERM signals are received.

1 files changed, 30 insertions, 1 deletions

diff --git a/pym/_emerge/PollScheduler.py b/pym/_emerge/PollScheduler.py
index e71350e5b..a319066c0 100644
--- a/pym/_emerge/PollScheduler.py
+++ b/pym/_emerge/PollScheduler.py
@@ -1,4 +1,4 @@
-# Copyright 1999-2010 Gentoo Foundation
+# Copyright 1999-2011 Gentoo Foundation
 # Distributed under the terms of the GNU General Public License v2
 
 import gzip
@@ -6,6 +6,11 @@ import logging
 import select
 import time
 
+try:
+	import threading
+except ImportError:
+	import dummy_threading as threading
+
 from portage import _encodings
 from portage import _unicode_encode
 from portage.util import writemsg_level
@@ -21,6 +26,8 @@ class PollScheduler(object):
 		__slots__ = ("output", "register", "schedule", "unregister")
 
 	def __init__(self):
+		self._terminated = threading.Event()
+		self._terminated_tasks = False
 		self._max_jobs = 1
 		self._max_load = None
 		self._jobs = 0
@@ -38,6 +45,24 @@ class PollScheduler(object):
 			schedule=self._schedule_wait,
 			unregister=self._unregister)
 
+	def terminate(self):
+		"""
+		Schedules asynchronous, graceful termination of the scheduler
+		at the earliest opportunity.
+
+		This method is thread-safe (and safe for signal handlers).
+		"""
+		self._terminated.set()
+
+	def _terminate_tasks(self):
+		"""
+		Send signals to terminate all tasks. This is called once
+		from the event dispatching thread. All task should be
+		cleaned up at the earliest opportunity, but not necessarily
+		before this method returns.
+		"""
+		raise NotImplementedError()
+
 	def _schedule(self):
 		"""
 		Calls _schedule_tasks() and automatically returns early from
@@ -120,6 +145,10 @@ class PollScheduler(object):
 		raises StopIteration if timeout is None and there are
 		no file descriptors to poll.
 		"""
+		if self._terminated.is_set() and \
+			not self._terminated_tasks:
+			self._terminated_tasks = True
+			self._terminate_tasks()
 		if not self._poll_event_queue:
 			self._poll(timeout)
 			if not self._poll_event_queue: