twisted/python/threadable.py

   1 # -*- test-case-name: twisted.python.test_threadable -*-
   2 # Copyright (c) Twisted Matrix Laboratories.
   3 # See LICENSE for details.
   4
   5
   6 """
   7 A module that will allow your program to be multi-threaded,
   8 micro-threaded, and single-threaded.  Currently microthreads are
   9 unimplemented.  The idea is to abstract away some commonly used
  10 functionality so that I don't have to special-case it in all programs.
  11 """
  12
  13
  14
  15 from twisted.python import hook
  16
  17 class DummyLock(object):
  18     """
  19     Hack to allow locks to be unpickled on an unthreaded system.
  20     """
  21
  22     def __reduce__(self):
  23         return (unpickle_lock, ())
  24
  25 def unpickle_lock():
  26     if threadingmodule is not None:
  27         return XLock()
  28     else:
  29         return DummyLock()
  30 unpickle_lock.__safe_for_unpickling__ = True
  31
  32 def _synchPre(self, *a, **b):
  33     if '_threadable_lock' not in self.__dict__:
  34         _synchLockCreator.acquire()
  35         if '_threadable_lock' not in self.__dict__:
  36             self.__dict__['_threadable_lock'] = XLock()
  37         _synchLockCreator.release()
  38     self._threadable_lock.acquire()
  39
  40 def _synchPost(self, *a, **b):
  41     self._threadable_lock.release()
  42
  43 def synchronize(*klasses):
  44     """Make all methods listed in each class' synchronized attribute synchronized.
  45
  46     The synchronized attribute should be a list of strings, consisting of the
  47     names of methods that must be synchronized. If we are running in threaded
  48     mode these methods will be wrapped with a lock.
  49     """
  50     if threadmodule is not None:
  51         for klass in klasses:
  52             for methodName in klass.synchronized:
  53                 hook.addPre(klass, methodName, _synchPre)
  54                 hook.addPost(klass, methodName, _synchPost)
  55
  56 def init(with_threads=1):
  57     """Initialize threading.
  58
  59     Don't bother calling this.  If it needs to happen, it will happen.
  60     """
  61     global threaded, _synchLockCreator, XLock
  62
  63     if with_threads:
  64         if not threaded:
  65             if threadmodule is not None:
  66                 threaded = True
  67
  68                 class XLock(threadingmodule._RLock, object):
  69                     def __reduce__(self):
  70                         return (unpickle_lock, ())
  71
  72                 _synchLockCreator = XLock()
  73             else:
  74                 raise RuntimeError("Cannot initialize threading, platform lacks thread support")
  75     else:
  76         if threaded:
  77             raise RuntimeError("Cannot uninitialize threads")
  78         else:
  79             pass
  80
  81 _dummyID = object()
  82 def getThreadID():
  83     if threadmodule is None:
  84         return _dummyID
  85     return threadmodule.get_ident()
  86
  87
  88 def isInIOThread():
  89     """Are we in the thread responsable for I/O requests (the event loop)?
  90     """
  91     return ioThread == getThreadID()
  92
  93
  94
  95 def registerAsIOThread():
  96     """Mark the current thread as responsable for I/O requests.
  97     """
  98     global ioThread
  99     ioThread = getThreadID()
 100
 101
 102 ioThread = None
 103 threaded = False
 104
 105
 106
 107 try:
 108     import thread as threadmodule
 109     import threading as threadingmodule
 110 except ImportError:
 111     threadmodule = None
 112     threadingmodule = None
 113 else:
 114     init(True)
 115
 116
 117
 118 __all__ = ['isInIOThread', 'registerAsIOThread', 'getThreadID', 'XLock']