[gentoo-portage-dev] [PATCH 1/6] EbuildBuildDir: add async_lock method (bug 614112)

[Zac Medico]

Asynchronoulsy handle locking of both the category directory and
build directory.

Bug: https://bugs.gentoo.org/614112
---
 pym/_emerge/EbuildBuildDir.py | 76 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)

diff --git a/pym/_emerge/EbuildBuildDir.py b/pym/_emerge/EbuildBuildDir.py
index 69f694992..9163deacf 100644
--- a/pym/_emerge/EbuildBuildDir.py
+++ b/pym/_emerge/EbuildBuildDir.py
@@ -1,6 +1,8 @@
 # Copyright 1999-2012 Gentoo Foundation
 # Distributed under the terms of the GNU General Public License v2
 
+import functools
+
 from _emerge.AsynchronousLock import AsynchronousLock
 
 import portage
@@ -84,6 +86,80 @@ class EbuildBuildDir(SlotObject):
 			except OSError:
 				pass
 
+	def async_lock(self):
+		"""
+		Acquire the lock asynchronously. Notification is available
+		via the add_done_callback method of the returned Future instance.
+
+		This raises an AlreadyLocked exception if async_lock() is called
+		while a lock is already held. In order to avoid this, call
+		async_unlock() or check whether the "locked" attribute is True
+		or False before calling async_lock().
+
+		@returns: Future, result is None
+		"""
+		if self._lock_obj is not None:
+			raise self.AlreadyLocked((self._lock_obj,))
+
+		dir_path = self.settings.get('PORTAGE_BUILDDIR')
+		if not dir_path:
+			raise AssertionError('PORTAGE_BUILDDIR is unset')
+		catdir = os.path.dirname(dir_path)
+		self._catdir = catdir
+		catdir_lock = AsynchronousLock(path=catdir, scheduler=self.scheduler)
+		builddir_lock = AsynchronousLock(path=dir_path, scheduler=self.scheduler)
+		result = self.scheduler.create_future()
+
+		def catdir_locked(catdir_lock):
+			try:
+				self._assert_lock(catdir_lock)
+			except AssertionError as e:
+				result.set_exception(e)
+				return
+
+			try:
+				portage.util.ensure_dirs(catdir,
+					gid=portage.portage_gid,
+					mode=0o70, mask=0)
+			except PortageException as e:
+				if not os.path.isdir(catdir):
+					result.set_exception(e)
+					return
+
+			builddir_lock.addExitListener(builddir_locked)
+			builddir_lock.start()
+
+		def builddir_locked(builddir_lock):
+			try:
+				self._assert_lock(builddir_lock)
+			except AssertionError as e:
+				catdir_lock.async_unlock.add_done_callback(
+					functools.partial(catdir_unlocked, exception=e))
+				return
+
+			self._lock_obj = builddir_lock
+			self.locked = True
+			self.settings['PORTAGE_BUILDDIR_LOCKED'] = '1'
+			catdir_lock.async_unlock().add_done_callback(catdir_unlocked)
+
+		def catdir_unlocked(future, exception=None):
+			if not (exception is None and future.exception() is None):
+				result.set_exception(exception or future.exception())
+			else:
+				result.set_result(None)
+
+		try:
+			portage.util.ensure_dirs(os.path.dirname(catdir),
+				gid=portage.portage_gid,
+				mode=0o70, mask=0)
+		except PortageException:
+			if not os.path.isdir(os.path.dirname(catdir)):
+				raise
+
+		catdir_lock.addExitListener(catdir_locked)
+		catdir_lock.start()
+		return result
+
 	def async_unlock(self):
 		"""
 		Release the lock asynchronously. Release notification is available
-- 
2.13.6