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Revision 39a8fddb1507593ebc8449ddcecd30ddaca69931 authored by Barry Warsaw on 28 May 2003, 23:03:30 UTC, committed by Barry Warsaw on 28 May 2003, 23:03:30 UTC
SF 742860: WeakKeyDictionary __delitem__ uses iterkeys Someone review this, please! Final releases are getting close, Fred (the weakref guy) won't be around until Tuesday, and the pre-patch code can indeed raise spurious RuntimeErrors in the presence of threads or mutating comparison functions. See the bug report for my confusions: I can't see any reason for why __delitem__ iterated over the keys. The new one-liner implementation is much faster, can't raise RuntimeError, and should be better-behaved in all respects wrt threads. New tests test_weak_keyed_bad_delitem and test_weak_keyed_cascading_deletes fail before this patch. Backported the tests and the patch.
1 parent 7496e18
Tip revision: 39a8fddb1507593ebc8449ddcecd30ddaca69931 authored by Barry Warsaw on 28 May 2003, 23:03:30 UTC
The backport gets Fred's seal of approval:
The backport gets Fred's seal of approval:
Tip revision: 39a8fdd
mutex.py
"""Mutual exclusion -- for use with module sched
A mutex has two pieces of state -- a 'locked' bit and a queue.
When the mutex is not locked, the queue is empty.
Otherwise, the queue contains 0 or more (function, argument) pairs
representing functions (or methods) waiting to acquire the lock.
When the mutex is unlocked while the queue is not empty,
the first queue entry is removed and its function(argument) pair called,
implying it now has the lock.
Of course, no multi-threading is implied -- hence the funny interface
for lock, where a function is called once the lock is aquired.
"""
class mutex:
def __init__(self):
"""Create a new mutex -- initially unlocked."""
self.locked = 0
self.queue = []
def test(self):
"""Test the locked bit of the mutex."""
return self.locked
def testandset(self):
"""Atomic test-and-set -- grab the lock if it is not set,
return true if it succeeded."""
if not self.locked:
self.locked = 1
return 1
else:
return 0
def lock(self, function, argument):
"""Lock a mutex, call the function with supplied argument
when it is acquired. If the mutex is already locked, place
function and argument in the queue."""
if self.testandset():
function(argument)
else:
self.queue.append((function, argument))
def unlock(self):
"""Unlock a mutex. If the queue is not empty, call the next
function with its argument."""
if self.queue:
function, argument = self.queue[0]
del self.queue[0]
function(argument)
else:
self.locked = 0
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