1 2 :mod:`mutex` --- Mutual exclusion support 3 ========================================= 4 5 .. module:: mutex 6 :synopsis: Lock and queue for mutual exclusion. 7 :deprecated: 8 9 .. deprecated:: 2.6 10 The :mod:`mutex` module has been removed in Python 3. 11 12 .. sectionauthor:: Moshe Zadka <moshez (a] zadka.site.co.il> 13 14 15 The :mod:`mutex` module defines a class that allows mutual-exclusion via 16 acquiring and releasing locks. It does not require (or imply) 17 :mod:`threading` or multi-tasking, though it could be useful for those 18 purposes. 19 20 The :mod:`mutex` module defines the following class: 21 22 23 .. class:: mutex() 24 25 Create a new (unlocked) mutex. 26 27 A mutex has two pieces of state --- a "locked" bit and a queue. When the mutex 28 is not locked, the queue is empty. Otherwise, the queue contains zero or more 29 ``(function, argument)`` pairs representing functions (or methods) waiting to 30 acquire the lock. When the mutex is unlocked while the queue is not empty, the 31 first queue entry is removed and its ``function(argument)`` pair called, 32 implying it now has the lock. 33 34 Of course, no multi-threading is implied -- hence the funny interface for 35 :meth:`lock`, where a function is called once the lock is acquired. 36 37 38 .. _mutex-objects: 39 40 Mutex Objects 41 ------------- 42 43 :class:`~mutex.mutex` objects have following methods: 44 45 46 .. method:: mutex.test() 47 48 Check whether the mutex is locked. 49 50 51 .. method:: mutex.testandset() 52 53 "Atomic" test-and-set, grab the lock if it is not set, and return ``True``, 54 otherwise, return ``False``. 55 56 57 .. method:: mutex.lock(function, argument) 58 59 Execute ``function(argument)``, unless the mutex is locked. In the case it is 60 locked, place the function and argument on the queue. See :meth:`unlock` for 61 explanation of when ``function(argument)`` is executed in that case. 62 63 64 .. method:: mutex.unlock() 65 66 Unlock the mutex if queue is empty, otherwise execute the first element in the 67 queue. 68 69
