[Twisted-Python] Re: [Twisted-commits] r13446 - After a lengthy discussion, revert to previous threaded behavior wrt registering as the IO thread

[Jp Calderone]

On Sun, 3 Apr 2005 13:31:08 -0400, James Y Knight <foom at fuhm.net> wrote:
>On Apr 3, 2005, at 1:58 AM, Jp Calderone wrote:
> > After a lengthy discussion, revert to previous threaded behavior wrt  
> > registering as the IO thread
> 
> > Modified: trunk/twisted/internet/posixbase.py
> > ======================================================================= 
> > =======
> > --- trunk/twisted/internet/posixbase.py	(original)
> > +++ trunk/twisted/internet/posixbase.py	Sat Apr  2 23:58:11 2005
> > @@ -155,7 +155,6 @@
> >          ReactorBase.__init__(self)
> >          if self.usingThreads or platformType == "posix":
> >              self.installWaker()
> > -        threadable.whenThreaded(threadable.registerAsIOThread)
> >
> >      def _handleSignals(self):
> >          """Install the signal handlers for the Twisted event loop."""
> 
> You **do** realize this means isInIOThread always returns false after  
> threading is enabled, if the reactor was started before threading was  
> enabled, right?

  Yes.  Fortunately this never actually happens.  When it becomes possible, we can think about fixing this behavior.

> 
> Something like the following should be run in the test suite. It has to  
> be in a separate process, though, to ensure it's in the incorrect  
> state, so something needs to be done about passing in the reactor to  
> run, also.
> 
> from twisted.python import threadable
> from twisted.internet import reactor
> 
> def testIsInIOThread():
>      print "1)", threadable.isInIOThread()
>      threadable.init(1)
>      print "2)", threadable.isInIOThread()
>      reactor.crash()
> 
> reactor.callWhenRunning(testIsInIOThread)
> reactor.run()

  Yes.  A unit test like that _would_ be nice...

> 
> > @@ -202,10 +201,6 @@
> >          self.startRunning(installSignalHandlers=installSignalHandlers)
> >          self.mainLoop()
> >
> > -    def iterate(self, delay=0):
> > -        threadable.registerAsIOThread()
> > -        ReactorBase.iterate(self, delay)
> > -
> >      def mainLoop(self):
> >          while self.running:
> >              try:
> 
> iterate() is the external API, I think it, like startRunning, should  
> also ensure the thread it's being called on is marked as the IO thread.

  Yes, however simply calling registerAsIOThread inside it is not a complete fix.  The understanding to which I came is that the previous incorrectness was preferable to the new incorrectness.

  Jp