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Revision 04097a628213df725c43b62b7be934e0bff6fb16 authored by Neal Norwitz on 13 June 2008, 06:03:25 UTC, committed by Neal Norwitz on 13 June 2008, 06:03:25 UTC
should implement less than or equal to (as the code does).
1 parent 705cd06
Tip revision: 04097a628213df725c43b62b7be934e0bff6fb16 authored by Neal Norwitz on 13 June 2008, 06:03:25 UTC
Fix typo in method name. The LT class implemented less than. The LE class
Fix typo in method name. The LT class implemented less than. The LE class
Tip revision: 04097a6
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.
"""
from warnings import warnpy3k
warnpy3k("the mutex module has been removed in Python 3.0", stacklevel=2)
del warnpy3k
from collections import deque
class mutex:
def __init__(self):
"""Create a new mutex -- initially unlocked."""
self.locked = 0
self.queue = deque()
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 True
else:
return False
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.popleft()
function(argument)
else:
self.locked = 0
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