Add a new AsynchronousLock class that uses the portage.locks module to

acquire a lock asynchronously, using a background thread.

4 files changed, 134 insertions, 0 deletions

diff --git a/pym/_emerge/AsynchronousLock.py b/pym/_emerge/AsynchronousLock.py
new file mode 100644
index 000000000..6eb90b4e4
--- /dev/null
+++ b/pym/_emerge/AsynchronousLock.py
@@ -0,0 +1,103 @@
+# Copyright 2010 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
+
+import dummy_threading
+import fcntl
+try:
+	import threading
+except ImportError:
+	import dummy_threading as threading
+
+from portage import os
+from portage.exception import TryAgain
+from portage.locks import lockfile, unlockfile
+from _emerge.AbstractPollTask import AbstractPollTask
+from _emerge.PollConstants import PollConstants
+
+class AsynchronousLock(AbstractPollTask):
+	"""
+	This uses the portage.locks module to acquire a lock asynchronously,
+	using a background thread. After the lock is acquired, the thread
+	writes to a pipe in order to notify a poll loop running in the main
+	thread.
+
+	If the threading module is unavailable then the dummy_threading
+	module will be used, and the lock will be acquired synchronously
+	(before the start() method returns).
+	"""
+
+	__slots__ = ('lock_obj', 'path',) + \
+		('_files', '_force_thread', '_force_dummy',
+		'_thread', '_reg_id',)
+
+	def _start(self):
+
+		if self._force_thread:
+			self._start_thread()
+			return
+
+		try:
+			self.lock_obj = lockfile(self.path,
+				wantnewlockfile=True, flags=os.O_NONBLOCK)
+		except TryAgain:
+			self._start_thread()
+		else:
+			self.returncode = os.EX_OK
+			self.wait()
+
+	def _start_thread(self):
+		pr, pw = os.pipe()
+		self._files = {}
+		self._files['pipe_read'] = os.fdopen(pr, 'rb', 0)
+		self._files['pipe_write'] = os.fdopen(pw, 'wb', 0)
+		for k, f in self._files.items():
+			fcntl.fcntl(f.fileno(), fcntl.F_SETFL,
+				fcntl.fcntl(f.fileno(), fcntl.F_GETFL) | os.O_NONBLOCK)
+		self._reg_id = self.scheduler.register(self._files['pipe_read'].fileno(),
+			PollConstants.POLLIN, self._output_handler)
+		self._registered = True
+		threading_mod = threading
+		if self._force_dummy:
+			threading_mod = dummy_threading
+		self._thread = threading_mod.Thread(target=self._run_lock)
+		self._thread.start()
+
+	def _run_lock(self):
+		self.lock_obj = lockfile(self.path, wantnewlockfile=True)
+		self._files['pipe_write'].write(b'\0')
+
+	def _output_handler(self, f, event):
+		buf = self._read_buf(self._files['pipe_read'], event)
+		if buf:
+			self._unregister()
+			self.returncode = os.EX_OK
+			self.wait()
+
+	def _wait(self):
+		if self.returncode is not None:
+			return self.returncode
+		if self._registered:
+			self.scheduler.schedule(self._reg_id)
+		return self.returncode
+
+	def unlock(self):
+		if self.lock_obj is None:
+			raise AssertionError('not locked')
+		unlockfile(self.lock_obj)
+		self.lock_obj = None
+
+	def _unregister(self):
+		self._registered = False
+
+		if self._thread is not None:
+			self._thread.join()
+			self._thread = None
+
+		if self._reg_id is not None:
+			self.scheduler.unregister(self._reg_id)
+			self._reg_id = None
+
+		if self._files is not None:
+			for f in self._files.values():
+				f.close()
+			self._files = None
diff --git a/pym/portage/tests/locks/__init__.py b/pym/portage/tests/locks/__init__.py
new file mode 100644
index 000000000..21a391aee
--- /dev/null
+++ b/pym/portage/tests/locks/__init__.py
@@ -0,0 +1,2 @@
+# Copyright 2010 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
diff --git a/pym/portage/tests/locks/__test__ b/pym/portage/tests/locks/__test__
new file mode 100644
index 000000000..e69de29bb
--- /dev/null
+++ b/pym/portage/tests/locks/__test__
diff --git a/pym/portage/tests/locks/test_asynchronous_lock.py b/pym/portage/tests/locks/test_asynchronous_lock.py
new file mode 100644
index 000000000..ac38462ed
--- /dev/null
+++ b/pym/portage/tests/locks/test_asynchronous_lock.py
@@ -0,0 +1,29 @@
+# Copyright 2010 Gentoo Foundation
+# Distributed under the terms of the GNU General Public License v2
+
+import shutil
+import tempfile
+
+from portage import os
+from portage.tests import TestCase
+from _emerge.AsynchronousLock import AsynchronousLock
+from _emerge.PollScheduler import PollScheduler
+
+class AsynchronousLockTestCase(TestCase):
+
+	def testAsynchronousLock(self):
+		scheduler = PollScheduler().sched_iface
+		tempdir = tempfile.mkdtemp()
+		try:
+			path = os.path.join(tempdir, 'lock_me')
+			for force_thread in (True, False):
+				for force_dummy in (True, False):
+					async_lock = AsynchronousLock(path=path,
+						scheduler=scheduler, _force_dummy=force_dummy,
+						_force_thread=force_thread)
+					async_lock.start()
+					async_lock.wait()
+					async_lock.unlock()
+					self.assertEqual(async_lock.returncode, os.EX_OK)
+		finally:
+			shutil.rmtree(tempdir)