69 lines
1.9 KiB
ReStructuredText
69 lines
1.9 KiB
ReStructuredText
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:mod:`mutex` --- Mutual exclusion support
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=========================================
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.. module:: mutex
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:synopsis: Lock and queue for mutual exclusion.
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:deprecated:
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.. deprecated:: 2.6
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The :mod:`mutex` module has been removed in Python 3.
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.. sectionauthor:: Moshe Zadka <moshez@zadka.site.co.il>
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The :mod:`mutex` module defines a class that allows mutual-exclusion via
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acquiring and releasing locks. It does not require (or imply)
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:mod:`threading` or multi-tasking, though it could be useful for those
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purposes.
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The :mod:`mutex` module defines the following class:
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.. class:: mutex()
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Create a new (unlocked) mutex.
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A mutex has two pieces of state --- a "locked" bit and a queue. When the mutex
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is not locked, the queue is empty. Otherwise, the queue contains zero or more
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``(function, argument)`` pairs representing functions (or methods) waiting to
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acquire the lock. When the mutex is unlocked while the queue is not empty, the
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first queue entry is removed and its ``function(argument)`` pair called,
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implying it now has the lock.
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Of course, no multi-threading is implied -- hence the funny interface for
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:meth:`lock`, where a function is called once the lock is acquired.
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.. _mutex-objects:
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Mutex Objects
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-------------
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:class:`~mutex.mutex` objects have following methods:
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.. method:: mutex.test()
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Check whether the mutex is locked.
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.. method:: mutex.testandset()
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"Atomic" test-and-set, grab the lock if it is not set, and return ``True``,
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otherwise, return ``False``.
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.. method:: mutex.lock(function, argument)
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Execute ``function(argument)``, unless the mutex is locked. In the case it is
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locked, place the function and argument on the queue. See :meth:`unlock` for
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explanation of when ``function(argument)`` is executed in that case.
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.. method:: mutex.unlock()
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Unlock the mutex if queue is empty, otherwise execute the first element in the
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queue.
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