AbstractPollTask: log exceptional events

Previously, when AbstractPollTask receives a POLLERR or POLLNVAL event,
it would silently cancel the task. Now it will generate a message like
this:

   !!! SpawnProcess received strange poll event: 8

The message is displayed via a new _log_poll_exception method, which
is overridden by AbstractEbuildProcess to log the message via elog.

This might help diagnose reported cases of SIGTERM signals killing
ebuild processes for no apparent reason:

   http://code.google.com/p/chromium-os/issues/detail?id=12968

1 files changed, 10 insertions, 1 deletions

diff --git a/pym/_emerge/AbstractPollTask.py b/pym/_emerge/AbstractPollTask.py
index 833ee3b4c..6cbf984b9 100644
--- a/pym/_emerge/AbstractPollTask.py
+++ b/pym/_emerge/AbstractPollTask.py
@@ -1,8 +1,10 @@
-# Copyright 1999-2010 Gentoo Foundation
+# Copyright 1999-2011 Gentoo Foundation
 # Distributed under the terms of the GNU General Public License v2
 
 import array
+import logging
 
+from portage.util import writemsg_level
 from _emerge.AsynchronousTask import AsynchronousTask
 from _emerge.PollConstants import PollConstants
 class AbstractPollTask(AsynchronousTask):
@@ -39,9 +41,16 @@ class AbstractPollTask(AsynchronousTask):
 	def _unregister(self):
 		raise NotImplementedError(self)
 
+	def _log_poll_exception(self, event):
+		writemsg_level(
+			"!!! %s received strange poll event: %s\n" % \
+			(self.__class__.__name__, event,),
+			level=logging.ERROR, noiselevel=-1)
+
 	def _unregister_if_appropriate(self, event):
 		if self._registered:
 			if event & self._exceptional_events:
+				self._log_poll_exception(event)
 				self._unregister()
 				self.cancel()
 			elif event & PollConstants.POLLHUP: