:mod:`mutex` --- Mutual exclusion support

.. module:: mutex
   :synopsis: Lock and queue for mutual exclusion.
   :deprecated:

.. deprecated:: 2.6
   The :mod:`mutex` module has been removed in Python 3.

.. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il>

The :mod:`mutex` module defines a class that allows mutual-exclusion via acquiring and releasing locks. It does not require (or imply) :mod:`threading` or multi-tasking, though it could be useful for those purposes.

The :mod:`mutex` module defines the following class:

Create a new (unlocked) mutex.

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 zero 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 :meth:`lock`, where a function is called once the lock is acquired.

.. method:: mutex.test()

   Check whether the mutex is locked.

.. method:: mutex.testandset()

   "Atomic" test-and-set, grab the lock if it is not set, and return ``True``,
   otherwise, return ``False``.

.. method:: mutex.lock(function, argument)

   Execute ``function(argument)``, unless the mutex is locked. In the case it is
   locked, place the function and argument on the queue. See :meth:`unlock` for
   explanation of when ``function(argument)`` is executed in that case.

.. method:: mutex.unlock()

   Unlock the mutex if queue is empty, otherwise execute the first element in the
   queue.