From 354e3edebebbdb23007db0e4af2dd294fecd570b Mon Sep 17 00:00:00 2001
From: Zac Medico <zmedico@gentoo.org>
Date: Thu, 3 Jul 2008 22:48:21 +0000
Subject: [PATCH] Bug #230469 - Implement non-blocking distlocks for
 --fetchonly. This adds a "flags" keyword parameter to the
 portage.locks.lock() function. Default is flags=0. If flags contains
 os.O_NONBLOCK then lock() will raise portage.exception.TryAgain instead of
 blocking. This new flags parameter is used to implement non-blocking
 distlocks in fetch() when fetchonly mode is enabled.

svn path=/main/trunk/; revision=10917
---
 pym/portage/__init__.py  | 26 +++++++++++++++++++-------
 pym/portage/exception.py |  4 ++++
 pym/portage/locks.py     | 13 +++++++++----
 3 files changed, 32 insertions(+), 11 deletions(-)

diff --git a/pym/portage/__init__.py b/pym/portage/__init__.py
index 9859e0f5e..6aa4d2664 100644
--- a/pym/portage/__init__.py
+++ b/pym/portage/__init__.py
@@ -3512,15 +3512,27 @@ def fetch(myuris, mysettings, listonly=0, fetchonly=0, locks_in_subdir=".locks",
 					from textwrap import wrap
 					waiting_msg = "\n".join(msg_prefix + line \
 						for line in wrap(waiting_msg, 65))
+
 				if locks_in_subdir:
-					file_lock = portage.locks.lockfile(
-						os.path.join(mysettings["DISTDIR"],
-						locks_in_subdir, myfile), wantnewlockfile=1,
-						waiting_msg=waiting_msg)
+					lock_file = os.path.join(mysettings["DISTDIR"],
+						locks_in_subdir, myfile)
+				else:
+					lock_file = myfile_path
+
+				lock_kwargs = {}
+				if fetchonly:
+					lock_kwargs["flags"] = os.O_NONBLOCK
 				else:
-					file_lock = portage.locks.lockfile(
-						myfile_path, wantnewlockfile=1,
-						waiting_msg=waiting_msg)
+					lock_kwargs["waiting_msg"] = waiting_msg
+
+				try:
+					file_lock = portage.locks.lockfile(myfile_path,
+						wantnewlockfile=1, **lock_kwargs)
+				except portage.exception.TryAgain:
+					writemsg((">>> File '%s' is already locked by " + \
+						"another fetcher. Continuing...\n") % myfile,
+						noiselevel=-1)
+					continue
 		try:
 			if not listonly:
 
diff --git a/pym/portage/exception.py b/pym/portage/exception.py
index d91584b73..66cd16244 100644
--- a/pym/portage/exception.py
+++ b/pym/portage/exception.py
@@ -57,6 +57,10 @@ class PermissionDenied(PortageException):
 	from errno import EACCES as errno
 	"""Permission denied"""
 
+class TryAgain(PortageException):
+	from errno import EAGAIN as errno
+	"""Try again"""
+
 class ReadOnlyFileSystem(PortageException):
 	"""Read-only file system"""
 
diff --git a/pym/portage/locks.py b/pym/portage/locks.py
index 004108eb7..000cd3495 100644
--- a/pym/portage/locks.py
+++ b/pym/portage/locks.py
@@ -5,7 +5,8 @@
 
 
 import errno, os, stat, time, types
-from portage.exception import InvalidData, DirectoryNotFound, FileNotFound
+from portage.exception import DirectoryNotFound, FileNotFound, \
+	InvalidData, TryAgain
 from portage.data import portage_gid
 from portage.util import writemsg
 from portage.localization import _
@@ -17,7 +18,8 @@ def lockdir(mydir):
 def unlockdir(mylock):
 	return unlockfile(mylock)
 
-def lockfile(mypath, wantnewlockfile=0, unlinkfile=0, waiting_msg=None):
+def lockfile(mypath, wantnewlockfile=0, unlinkfile=0,
+	waiting_msg=None, flags=0):
 	"""Creates all dirs upto, the given dir. Creates a lockfile
 	for the given directory as the file: directoryname+'.portage_lockfile'."""
 	import fcntl
@@ -54,7 +56,8 @@ def lockfile(mypath, wantnewlockfile=0, unlinkfile=0, waiting_msg=None):
 			except OSError, e:
 				if e[0] == 2: # No such file or directory
 					return lockfile(mypath, wantnewlockfile=wantnewlockfile,
-						unlinkfile=unlinkfile, waiting_msg=waiting_msg)
+						unlinkfile=unlinkfile, waiting_msg=waiting_msg,
+						flags=flags)
 				else:
 					writemsg("Cannot chown a lockfile. This could cause inconvenience later.\n");
 			os.umask(old_mask)
@@ -78,6 +81,8 @@ def lockfile(mypath, wantnewlockfile=0, unlinkfile=0, waiting_msg=None):
 			raise
 		if e.errno in (errno.EACCES, errno.EAGAIN):
 			# resource temp unavailable; eg, someone beat us to the lock.
+			if flags & os.O_NONBLOCK:
+				raise TryAgain(mypath)
 			if waiting_msg is None:
 				if isinstance(mypath, int):
 					print "waiting for lock on fd %i" % myfd
@@ -114,7 +119,7 @@ def lockfile(mypath, wantnewlockfile=0, unlinkfile=0, waiting_msg=None):
 		writemsg("lockfile recurse\n",1)
 		lockfilename, myfd, unlinkfile, locking_method = lockfile(
 			mypath, wantnewlockfile=wantnewlockfile, unlinkfile=unlinkfile,
-			waiting_msg=waiting_msg)
+			waiting_msg=waiting_msg, flags=flags)
 
 	writemsg(str((lockfilename,myfd,unlinkfile))+"\n",1)
 	return (lockfilename,myfd,unlinkfile,locking_method)
-- 
2.26.2