``mutex`` --- Mutual exclusion support
**************************************

Deprecated since version The: ``mutex`` module has been removed in
Python 3.0.

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

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

class class mutex.mutex

   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 ``lock()``, where a function is called once the lock
   is acquired.


Mutex Objects
=============

``mutex`` objects have following methods:

mutex.test()

   Check whether the mutex is locked.

mutex.testandset()

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

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 ``unlock()`` for explanation of when ``function(argument)`` is
   executed in that case.

mutex.unlock()

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