mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-08-24 10:45:53 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 8

Fix bug 544473 - "Queue module can deadlock".

Browse source 
Use try/finally to ensure all Queue locks remain stable.
Includes test case.  Bugfix candidate.
This commit is contained in:
Mark Hammond 2002-04-19 00:11:32 +00:00
parent 08d821582f
commit 3b959dbcaf
2 changed files with 191 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

47
Lib/Queue.py
View file

@ -55,13 +55,24 @@ class Queue:
elif not self.fsema.acquire(0):
raise Full
self.mutex.acquire()
was_empty = self._empty()
self._put(item)
if was_empty:
self.esema.release()
if not self._full():
self.fsema.release()
self.mutex.release()
release_fsema = True
try:
was_empty = self._empty()
self._put(item)
# If we fail before here, the empty state has
# not changed, so we can skip the release of esema
if was_empty:
self.esema.release()
# If we fail before here, the queue can not be full, so
# release_full_sema remains True
release_fsema = not self._full()
finally:
# Catching system level exceptions here (RecursionDepth,
# OutOfMemory, etc) - so do as little as possible in terms
# of Python calls.
if release_fsema:
self.fsema.release()
self.mutex.release()
def put_nowait(self, item):
"""Put an item into the queue without blocking.
@ -84,13 +95,21 @@ class Queue:
elif not self.esema.acquire(0):
raise Empty
self.mutex.acquire()
was_full = self._full()
item = self._get()
if was_full:
self.fsema.release()
if not self._empty():
self.esema.release()
self.mutex.release()
release_esema = True
try:
was_full = self._full()
item = self._get()
# If we fail before here, the full state has
# not changed, so we can skip the release of fsema
if was_full:
self.fsema.release()
# Failure means empty state also unchanged - release_esema
# remains True.
release_esema = not self._empty()
finally:
if release_esema:
self.esema.release()
self.mutex.release()
return item
def get_nowait(self):