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Subject: RE: Threading issue in cygwin python 2.5.1-2 ?
Date: Sun, 27 Jan 2008 13:38:13 -0000
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On 26 January 2008 02:27, Jim Kleckner wrote:

>> Thanks for providing a testcase.  Should be fixed in CVS:
>> <http://www.cygwin.com/ml/cygwin-patches/2007-q3/msg00013.html>
> 
> I have a python application that works fine
> on Linux and Mac but fails with Cygwin.
> 
> I tried using snapshot:
>  cygwin-inst-20080122.tar.bz2
> but it still fails.  (In addition, stdout appears to not get flushed in
> that snapshot).

  That's presumably a snapshot of 1.7.0, which is pretty work-in-progressy at
the moment?

> Is it the case that the patch to the header
> file requires the recompilation of applications
> and libraries that use threading to make them work?
> 
> See these messages for context:
>  http://cygwin.com/ml/cygwin/2007-09/msg00120.html
>  http://cygwin.com/ml/cygwin/2006-12/msg00451.html
>  http://cygwin.com/ml/cygwin/2006-05/msg00125.html

  The two testcases I found in those threads (attached) both WJFFM under
cygwin 1.5.25-7 but fail under 1.5.23-2.  If you can reproduce that and your
program still fails, it's probably a different issue.


    cheers,
      DaveK

-- 
Can't think of a witty .sigline today....

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#!python
# From http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/82965
"""
This recipe describes how to handle asynchronous I/O in an environment where
you are running Tkinter as the graphical user interface. Tkinter is safe
to use as long as all the graphics commands are handled in a single thread.
Since it is more efficient to make I/O channels to block and wait for somet=
hing
to happen rather than poll at regular intervals, we want I/O to be handled
in separate threads. These can communicate in a threasafe way with the main,
GUI-oriented process through one or several queues. In this solution the GUI
still has to make a poll at a reasonable interval, to check if there is
something in the queue that needs processing. Other solutions are possible,
but they add a lot of complexity to the application.

Created by Jacob Hall?n, AB Strakt, Sweden. 2001-10-17
"""
import Tkinter
import time
import threading
import random
import Queue

class GuiPart:
    def __init__(self, master, queue, endCommand):
        self.queue =3D queue
        # Set up the GUI
        console =3D Tkinter.Button(master, text=3D'Done', command=3DendComm=
and)
        console.pack()
        # Add more GUI stuff here

    def processIncoming(self):
        """
        Handle all the messages currently in the queue (if any).
        """
        while self.queue.qsize():
            try:
                msg =3D self.queue.get(0)
                # Check contents of message and do what it says
                # As a test, we simply print it
                print msg
            except Queue.Empty:
                pass
        print "done processIncoming"

class ThreadedClient:
    """
    Launch the main part of the GUI and the worker thread. periodicCall and
    endApplication could reside in the GUI part, but putting them here
    means that you have all the thread controls in a single place.
    """
    def __init__(self, master):
        """
        Start the GUI and the asynchronous threads. We are in the main
        (original) thread of the application, which will later be used by
        the GUI. We spawn a new thread for the worker.
        """
        print "__init__"
        self.master =3D master

        # Create the queue
        print "Queue"
        self.queue =3D Queue.Queue()

        # Set up the GUI part
        print "GuiPart"
        self.gui =3D GuiPart(master, self.queue, self.endApplication)

        # Set up the thread to do asynchronous I/O
        # More can be made if necessary
        self.running =3D 1
        print "running"
    	self.thread1 =3D threading.Thread(target=3Dself.workerThread1)
        self.thread1.start()

        # Start the periodic call in the GUI to check if the queue contains
        # anything
        print "peridicCall"
        self.periodicCall()

    def periodicCall(self):
        """
        Check every 100 ms if there is something new in the queue.
        """
        print "processIncoming"
        self.gui.processIncoming()
        if not self.running:
            # This is the brutal stop of the system. You may want to do
            # some cleanup before actually shutting it down.
            print "exiting"
            import sys
            sys.exit(1)
        print "self.master.after"
        self.master.after(100, self.periodicCall)
        print "done periodicCall"

    def workerThread1(self):
        """
        This is where we handle the asynchronous I/O. For example, it may be
        a 'select()'.
        One important thing to remember is that the thread has to yield
        control.
        """
        print "workerThread1"
        while self.running:
            # To simulate asynchronous I/O, we create a random number at
            # random intervals. Replace the following 2 lines with the real
            # thing.
            time.sleep(rand.random() * 0.3)
            msg =3D rand.random()
            self.queue.put(msg)

    def endApplication(self):
        print "endApplication"
        self.running =3D 0

rand =3D random.Random()
root =3D Tkinter.Tk()

client =3D ThreadedClient(root)
root.mainloop()


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#!python
# Demonstrate python/Tkinter threading bug

import sys, types, os, threading
import Tkinter as TK
from time import sleep


class App:

    def __init__(self, root):

        self.root =3D root
        self.update_loop()


        # Start a second thread, to do whatever...
        self.thread =3D threading.Thread(target=3Dself.second_thread)
        self.thread.start()


    def update_loop(self):
        print >>sys.stderr, "*** update_loop"
        self.root.after(400, self.update_loop)


    def second_thread(self):
        sleep(100)


if __name__ =3D=3D "__main__":
    root =3D TK.Tk()
    app =3D App(root)
    root.mainloop();


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