Add a PollScheduler._schedule_waitpid() method for SubProcess._wait()

 to use as an alternative to hanging up the scheduler in a blocking
waitpid call.

4 files changed, 49 insertions, 4 deletions

diff --git a/pym/_emerge/PollScheduler.py b/pym/_emerge/PollScheduler.py
index ea8ebaacf..7f972e972 100644
--- a/pym/_emerge/PollScheduler.py
+++ b/pym/_emerge/PollScheduler.py
@@ -5,6 +5,7 @@ import logging
 import select
 import time
 
+from portage import os
 from portage.util import writemsg_level
 
 from _emerge.SlotObject import SlotObject
@@ -15,7 +16,7 @@ from _emerge.PollSelectAdapter import PollSelectAdapter
 class PollScheduler(object):
 
 	class _sched_iface_class(SlotObject):
-		__slots__ = ("register", "schedule", "unregister")
+		__slots__ = ("register", "schedule", "schedule_waitpid", "unregister")
 
 	def __init__(self):
 		self._max_jobs = 1
@@ -229,6 +230,36 @@ class PollScheduler(object):
 
 		return event_handled
 
+	def _schedule_waitpid(self, pid):
+		"""
+		Schedule until waitpid returns process status
+		for the given pid, and return the result from waitpid.
+		This is meant to be called as a last resort, since
+		it won't return until the process exits. This can raise
+		OSError from the waitpid call (typically errno.ECHILD).
+		@type pid: int
+		@param pid: the pid of the child process to wait for
+		"""
+		event_handlers = self._poll_event_handlers
+
+		try:
+			while event_handlers:
+				f, event = self._next_poll_event()
+				try:
+					handler, reg_id = event_handlers[f]
+				except KeyError:
+					pass
+				else:
+					handler(f, event)
+					wait_retval = os.waitpid(pid, os.WNOHANG)
+					if wait_retval != (0, 0):
+						return wait_retval
+				self.schedule()
+		except StopIteration:
+			pass
+
+		# Once scheduling is exhaused, do a blocking waitpid.
+		return os.waitpid(pid, 0)
 
 _can_poll_device = None
 
diff --git a/pym/_emerge/QueueScheduler.py b/pym/_emerge/QueueScheduler.py
index 8e1837c03..a65a90f06 100644
--- a/pym/_emerge/QueueScheduler.py
+++ b/pym/_emerge/QueueScheduler.py
@@ -21,7 +21,8 @@ class QueueScheduler(PollScheduler):
 		self.sched_iface = self._sched_iface_class(
 			register=self._register,
 			schedule=self._schedule_wait,
-			unregister=self._unregister)
+			unregister=self._unregister,
+			schedule_waitpid=self._schedule_waitpid)
 
 		self._queues = []
 		self._schedule_listeners = []
diff --git a/pym/_emerge/Scheduler.py b/pym/_emerge/Scheduler.py
index ae9cbcaa8..8d00a6f92 100644
--- a/pym/_emerge/Scheduler.py
+++ b/pym/_emerge/Scheduler.py
@@ -78,6 +78,7 @@ class Scheduler(PollScheduler):
 	class _iface_class(SlotObject):
 		__slots__ = ("dblinkEbuildPhase", "dblinkDisplayMerge",
 			"dblinkElog", "dblinkEmergeLog", "fetch", "register", "schedule",
+			"schedule_waitpid",
 			"scheduleSetup", "scheduleUnpack", "scheduleYield",
 			"unregister")
 
@@ -210,6 +211,7 @@ class Scheduler(PollScheduler):
 			dblinkEmergeLog=self._dblink_emerge_log,
 			fetch=fetch_iface, register=self._register,
 			schedule=self._schedule_wait,
+			schedule_waitpid=self._schedule_waitpid,
 			scheduleSetup=self._schedule_setup,
 			scheduleUnpack=self._schedule_unpack,
 			scheduleYield=self._schedule_yield,
diff --git a/pym/_emerge/SubProcess.py b/pym/_emerge/SubProcess.py
index 9d75f0ea1..177ae3f92 100644
--- a/pym/_emerge/SubProcess.py
+++ b/pym/_emerge/SubProcess.py
@@ -81,14 +81,25 @@ class SubProcess(AbstractPollTask):
 				return self.returncode
 
 		try:
-			wait_retval = os.waitpid(self.pid, 0)
+			wait_retval = os.waitpid(self.pid, os.WNOHANG)
 		except OSError as e:
 			if e.errno != errno.ECHILD:
 				raise
 			del e
 			self._set_returncode((self.pid, 1))
 		else:
-			self._set_returncode(wait_retval)
+			if wait_retval != (0, 0):
+				self._set_returncode(wait_retval)
+			else:
+				try:
+					wait_retval = self.scheduler.schedule_waitpid(self.pid)
+				except OSError as e:
+					if e.errno != errno.ECHILD:
+						raise
+					del e
+					self._set_returncode((self.pid, 1))
+				else:
+					self._set_returncode(wait_retval)
 
 		return self.returncode