From 868d0c6ccdc7f5d7e689d13dacd4a1cf17e6977d Mon Sep 17 00:00:00 2001
From: Joshua Harlow <harlowja@yahoo-inc.com>
Date: Sun, 1 Sep 2013 17:29:53 -0700
Subject: [PATCH] Reader/writer no longer used

Remove the reader/writer lock as it is no
longer used and if it is needed I would
rather thing of other ways to do this as
getting the reader/writer lock usage incorrect
will mean deadlock.

Change-Id: I4518c25e65626dc5a77f4e899c258ff9da76fea1
---
 taskflow/utils.py | 78 -----------------------------------------------
 1 file changed, 78 deletions(-)

diff --git a/taskflow/utils.py b/taskflow/utils.py
index 6aa8d6234..06d0a64b8 100644
--- a/taskflow/utils.py
+++ b/taskflow/utils.py
@@ -18,7 +18,6 @@
 #    under the License.
 
 import collections
-import contextlib
 import copy
 import inspect
 import logging
@@ -506,80 +505,3 @@ class RollbackAccumulator(object):
     def __exit__(self, type, value, tb):
         if any((value, type, tb)):
             self.rollback(value)
-
-
-class ReaderWriterLock(object):
-    """A simple reader-writer lock.
-
-    Several readers can hold the lock simultaneously, and only one writer.
-    Write locks have priority over reads to prevent write starvation.
-
-    Public domain @ http://majid.info/blog/a-reader-writer-lock-for-python/
-    """
-
-    def __init__(self):
-        self.rwlock = 0
-        self.writers_waiting = 0
-        self.monitor = threading.Lock()
-        self.readers_ok = threading.Condition(self.monitor)
-        self.writers_ok = threading.Condition(self.monitor)
-
-    @contextlib.contextmanager
-    def acquire(self, read=True):
-        """Acquire a read or write lock in a context manager."""
-        try:
-            if read:
-                self.acquire_read()
-            else:
-                self.acquire_write()
-            yield self
-        finally:
-            self.release()
-
-    def acquire_read(self):
-        """Acquire a read lock.
-
-        Several threads can hold this typeof lock.
-        It is exclusive with write locks.
-        """
-
-        self.monitor.acquire()
-        while self.rwlock < 0 or self.writers_waiting:
-            self.readers_ok.wait()
-        self.rwlock += 1
-        self.monitor.release()
-
-    def acquire_write(self):
-        """Acquire a write lock.
-
-        Only one thread can hold this lock, and only when no read locks
-        are also held.
-        """
-
-        self.monitor.acquire()
-        while self.rwlock != 0:
-            self.writers_waiting += 1
-            self.writers_ok.wait()
-            self.writers_waiting -= 1
-        self.rwlock = -1
-        self.monitor.release()
-
-    def release(self):
-        """Release a lock, whether read or write."""
-
-        self.monitor.acquire()
-        if self.rwlock < 0:
-            self.rwlock = 0
-        else:
-            self.rwlock -= 1
-        wake_writers = self.writers_waiting and self.rwlock == 0
-        wake_readers = self.writers_waiting == 0
-        self.monitor.release()
-        if wake_writers:
-            self.writers_ok.acquire()
-            self.writers_ok.notify()
-            self.writers_ok.release()
-        elif wake_readers:
-            self.readers_ok.acquire()
-            self.readers_ok.notifyAll()
-            self.readers_ok.release()