/Doc/library/mutex.rst
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- :mod:`mutex` --- Mutual exclusion support
- =========================================
- .. module:: mutex
- :synopsis: Lock and queue for mutual exclusion.
- :deprecated:
- .. deprecated::
- The :mod:`mutex` module has been removed in Python 3.0.
- .. 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:
- .. class:: 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
- :meth:`lock`, where a function is called once the lock is acquired.
- .. _mutex-objects:
- Mutex Objects
- -------------
- :class:`mutex` objects have following methods:
- .. 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.