PollScheduler: use idle_add to check termination

This fixes a regression in termination signal handling since commit
8c1fcf5a9ba9fa4d406a4d0cc284fe73a84f5a63, which cause termination
signals to be ignored until a running job had exited. This regression
is not really noticeable for Ctrl-C handling, since in that case the
SIGINT propagets to subprocesses, causing them to exit and trigger a
_schedule() call whichtriggers a termination check.

2 files changed, 41 insertions, 22 deletions

diff --git a/pym/_emerge/PollScheduler.py b/pym/_emerge/PollScheduler.py
index e270e6ad0..1db68072c 100644
--- a/pym/_emerge/PollScheduler.py
+++ b/pym/_emerge/PollScheduler.py
@@ -59,11 +59,30 @@ class PollScheduler(object):
 		"""
 		self._terminated.set()
 
+	def _termination_check(self):
+		"""
+		Calls _terminate_tasks() if appropriate. It's guaranteed not to
+		call it while _schedule_tasks() is being called. The check should
+		be executed for each iteration of the event loop, for response to
+		termination signals at the earliest opportunity. It always returns
+		True, for continuous scheduling via idle_add.
+		"""
+		if not self._scheduling and \
+			self._terminated.is_set() and \
+			not self._terminated_tasks:
+			self._scheduling = True
+			try:
+				self._terminated_tasks = True
+				self._terminate_tasks()
+			finally:
+				self._scheduling = False
+		return True
+
 	def _terminate_tasks(self):
 		"""
 		Send signals to terminate all tasks. This is called once
-		from self._schedule() in the event dispatching thread. This
-		prevents it from being called while the _schedule_tasks()
+		from _keep_scheduling() or _is_work_scheduled() in the event
+		dispatching thread. It will not be called while the _schedule_tasks()
 		implementation is running, in order to avoid potential
 		interference. All tasks should be cleaned up at the earliest
 		opportunity, but not necessarily before this method returns.
@@ -107,31 +126,29 @@ class PollScheduler(object):
 			return False
 		self._scheduling = True
 		try:
-
-			if self._terminated.is_set() and \
-				not self._terminated_tasks:
-				self._terminated_tasks = True
-				self._terminate_tasks()
-
 			self._schedule_tasks()
 		finally:
 			self._scheduling = False
 
 	def _main_loop(self):
-		# Populate initial event sources. We only need to do
-		# this once here, since it can be called during the
-		# loop from within event handlers.
-		self._schedule()
-
-		# Loop while there are jobs to be scheduled.
-		while self._keep_scheduling():
-			self.sched_iface.iteration()
-
-		# Clean shutdown of previously scheduled jobs. In the
-		# case of termination, this allows for basic cleanup
-		# such as flushing of buffered output to logs.
-		while self._is_work_scheduled():
-			self.sched_iface.iteration()
+		term_check_id = self.sched_iface.idle_add(self._termination_check)
+		try:
+			# Populate initial event sources. We only need to do
+			# this once here, since it can be called during the
+			# loop from within event handlers.
+			self._schedule()
+
+			# Loop while there are jobs to be scheduled.
+			while self._keep_scheduling():
+				self.sched_iface.iteration()
+
+			# Clean shutdown of previously scheduled jobs. In the
+			# case of termination, this allows for basic cleanup
+			# such as flushing of buffered output to logs.
+			while self._is_work_scheduled():
+				self.sched_iface.iteration()
+		finally:
+			self.sched_iface.source_remove(term_check_id)
 
 	def _is_work_scheduled(self):
 		return bool(self._running_job_count())
diff --git a/pym/_emerge/QueueScheduler.py b/pym/_emerge/QueueScheduler.py
index 731a677e5..730bd787d 100644
--- a/pym/_emerge/QueueScheduler.py
+++ b/pym/_emerge/QueueScheduler.py
@@ -43,6 +43,7 @@ class QueueScheduler(PollScheduler):
 			timeout_callback.timeout_id = self.sched_iface.timeout_add(
 				timeout, timeout_callback)
 
+		term_check_id = self.sched_iface.idle_add(self._termination_check)
 		try:
 			while not (timeout_callback is not None and
 				timeout_callback.timed_out):
@@ -59,6 +60,7 @@ class QueueScheduler(PollScheduler):
 				timeout_callback.timed_out):
 				self.sched_iface.iteration()
 		finally:
+			self.sched_iface.source_remove(term_check_id)
 			if timeout_callback is not None:
 				self.sched_iface.unregister(timeout_callback.timeout_id)