[Python-bugs-list] [ python-Bugs-566037 ] Popen exectuion blocking w/threads

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Bugs item #566037, was opened at 2002-06-07 17:07
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Category: Threads
Group: Python 2.2.1
Status: Open
Resolution: None
Priority: 3
Submitted By: Martin Stoufer (mstoufer)
Assigned to: Nobody/Anonymous (nobody)
Summary: Popen exectuion blocking w/threads

Initial Comment:
The following unit test hangs after the first two lines
of output. This is wholly reproducible (for us) under
2.2.1 and totaly unreproducible under 2.1. We have both
interpreters installed on a RH7.2 PC with linkings
against the apparent same /lib/libthread.so.0

import os, threading,time, sys
def read_output(self, cmd, timeout):
        print "run: %s" % cmd
        (inf,outf) = os.popen4(cmd)
        print "started! out_fd=%d" % outf.fileno()
        while 1:
            line = outf.readline()
            if line == "": break
            print len(line),line
            sys.stdout.flush()
        return
if __name__ == '__main__': 
    thr =
threading.Thread(target=read_output,args=(1,"ping -c 5
www.mit.edu",0))
    thr.start()
    print "Started thread"
    while 1: time.sleep(1)

mstoufer@dpsslx05(3)>ldd /usr/local/bin/python2.{1,2}
/usr/local/bin/python2.1:
	libpthread.so.0 => /lib/libpthread.so.0 (0x40029000)
	libdl.so.2 => /lib/libdl.so.2 (0x40040000)
	libutil.so.1 => /lib/libutil.so.1 (0x40044000)
	libstdc++-libc6.1-2.so.3 =>
/usr/local/lib/libstdc++-libc6.1-2.so.3 (0x40047000)
	libm.so.6 => /lib/libm.so.6 (0x4008f000)
	libc.so.6 => /lib/libc.so.6 (0x400b1000)
	/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
/usr/local/bin/python2.2:
	libdl.so.2 => /lib/libdl.so.2 (0x40029000)
	libpthread.so.0 => /lib/libpthread.so.0 (0x4002d000)
	libutil.so.1 => /lib/libutil.so.1 (0x40044000)
	libm.so.6 => /lib/libm.so.6 (0x40047000)
	libc.so.6 => /lib/libc.so.6 (0x4006a000)
	/lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)

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Comment By: Martin Stoufer (mcstoufer)
Date: 2002-06-11 21:10

Message:
Logged In: YES 
user_id=243169

This same issue arises when any subprocess is declared that makes 
more than 1 network read/write. From the system side, the Ping process 
is simply sleeping; we feel that the process is looking for the pipe to 
empty so it can finish it's write to stdout.

Replacing cmd with 'ping -c 1  www.mit.edu' works everytime. 
Replacing cmd with 'echo\'Hello. world\'' works as well.

We have beeen using a therading model similar to this under 2.1 and it 
has been quite robust in its execution. Is it possible that this is a 
compile-time issue with the thread linking?


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Comment By: Guido van Rossum (gvanrossum)
Date: 2002-06-10 12:39

Message:
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Mixing forks and threads is often asking for trouble...

Does this also hang with another command that produces more
than two lines of output, or is it limited to ping?

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Comment By: Martin v. Löwis (loewis)
Date: 2002-06-09 01:32

Message:
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I can't reproduce this on a SuSE system, either (which has
glibc 2.2.5), so I'm tempted to declare it a glibc 2.1 bug.

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Comment By: Mark Hammond (mhammond)
Date: 2002-06-07 22:42

Message:
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Just noting that current CVS Python works fine on Windows,
but also hangs on RH7.  My Linux debuggings skills are such
that I can offer no further help ;)

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