Python hang

[Daniel Tripp <dt123 at dt dot theorem dot ca>]

I'm having a problem with blocking I/O in python.

It is reproduced by the program below.  When I run it on cygwin, it prints 
"About to read fifo..." then "About to write regular file..." then hangs. 
Ctrl-C and Ctrl-Z don't kill it - I've had to kill it with Task Manager.

For comparison, I've run it on a couple of Ubuntu boxes, and it prints 
"About to read fifo..." then "About to write regular file..." then 
"Finished writing regular file." then it exits normally.

If anyone can shed some light on why this is happening, I'd appreciate it.

Output of "cygcheck -s -v -r" is attached.


#!/usr/bin/env python

import sys, os, tempfile, threading, time

tmpdir = tempfile.mkdtemp()

def write_regular_file():
  print 'About to write regular file...'
  try:
    filename = os.path.join(tmpdir, 'regular-file')
    with open(filename, 'w') as fout:
      fout.write('file contents')
  finally:
    print 'Finished writing regular file.'

def create_and_read_fifo_in_separate_thread():
  fifo_filename = os.path.join(tmpdir, 'fifo')
  os.mkfifo(fifo_filename)
  def run():
    print 'About to read fifo...'
    with open(fifo_filename) as fin:
      fin.read()
    # This will never print, even if the test is successful:
    print 'Finished reading fifo.'
  thread = threading.Thread(target=run)
  thread.daemon = True
  thread.start()

if __name__ == '__main__':

  create_and_read_fifo_in_separate_thread()
  time.sleep(1)
  write_regular_file()

Attachment: cygcheck.out
Description: Text document

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple