From 646c21b911ca2d14fb0f8489ff22e05fe9c4199a Mon Sep 17 00:00:00 2001
From: Zac Medico <zmedico@gentoo.org>
Date: Sat, 7 May 2011 19:57:29 -0700
Subject: Add vardbapi reentrant lock/unlock methods.

---
 pym/portage/dbapi/vartree.py | 54 +++++++++++++++++++++++++++++++-------------
 1 file changed, 38 insertions(+), 16 deletions(-)

(limited to 'pym')

diff --git a/pym/portage/dbapi/vartree.py b/pym/portage/dbapi/vartree.py
index 7f9fb9936..bc9916e31 100644
--- a/pym/portage/dbapi/vartree.py
+++ b/pym/portage/dbapi/vartree.py
@@ -131,6 +131,10 @@ class vardbapi(dbapi):
 				DeprecationWarning, stacklevel=2)
 
 		self._eroot = settings['EROOT']
+		self._dbroot = self._eroot + VDB_PATH
+		self._lock = None
+		self._lock_count = 0
+
 		if vartree is None:
 			vartree = portage.db[self.root]["vartree"]
 		self.vartree = vartree
@@ -167,6 +171,38 @@ class vardbapi(dbapi):
 			rValue = _os.path.join(rValue, filename)
 		return rValue
 
+	def lock(self):
+		"""
+		Acquire a reentrant lock, blocking, for cooperation with concurrent
+		processes. State is inherited by subprocesses, allowing subprocesses
+		to reenter a lock that was acquired by a parent process. However,
+		a lock can be released only by the same process that acquired it.
+		"""
+		if self._lock_count:
+			self._lock_count += 1
+		else:
+			if self._lock is not None:
+				raise AssertionError("already locked")
+			# At least the parent needs to exist for the lock file.
+			ensure_dirs(self._dbroot)
+			self._lock = lockdir(self._dbroot)
+			self._lock_count += 1
+
+	def unlock(self):
+		"""
+		Release a lock, decrementing the recursion level. Each unlock() call
+		must be matched with a prior lock() call, or else an AssertionError
+		will be raised if unlock() is called while not locked.
+		"""
+		if self._lock_count > 1:
+			self._lock_count -= 1
+		else:
+			if self._lock is None:
+				raise AssertionError("not locked")
+			self._lock_count = 0
+			unlockdir(self._lock)
+			self._lock = None
+
 	def _bump_mtime(self, cpv):
 		"""
 		This is called before an after any modifications, so that consumers
@@ -1226,10 +1262,6 @@ class dblink(object):
 		self.dbpkgdir = self.dbcatdir+"/"+pkg
 		self.dbtmpdir = self.dbcatdir+"/-MERGING-"+pkg
 		self.dbdir = self.dbpkgdir
-
-		self._lock_vdb = None
-		self._lock_vdb_count = 0
-
 		self.settings = mysettings
 		self._verbose = self.settings.get("PORTAGE_VERBOSE") == "1"
 
@@ -1269,20 +1301,10 @@ class dblink(object):
 		self._get_protect_obj().updateprotect()
 
 	def lockdb(self):
-		if self._lock_vdb_count:
-			self._lock_vdb_count += 1
-		else:
-			# At least the parent needs to exist for the lock file.
-			ensure_dirs(self.dbroot)
-			self._lock_vdb = lockdir(self.dbroot)
+		self.vartree.dbapi.lock()
 
 	def unlockdb(self):
-		if self._lock_vdb_count > 1:
-			self._lock_vdb_count -= 1
-		else:
-			self._lock_vdb_count = 0
-			unlockdir(self._lock_vdb)
-			self._lock_vdb = None
+		self.vartree.dbapi.unlock()
 
 	def getpath(self):
 		"return path to location of db information (for >>> informational display)"
-- 
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