[issue3792] Module variable overridden in child processes with multiprocessing

[Steve Smith]

New submission from Steve Smith <[EMAIL PROTECTED]>:

The process variable 'p' is leaking into sub-processes when using the
multiprocessing modules.  The following code demonstrates the problem:

import sys
from multiprocessing import Process

p = 'Correct'

def test():
print "Got 'p' of", p

if __name__ == '__main__':
if len(sys.argv) == 2 and sys.argv[1] == '-m':
p = Process(target=test)
p.start()
p.join()
else:
test()

Running this in SP and MP mode shows the leakage:

ssmith$ /opt/python-svn/bin/python mpbug.py 
Got 'p' of Correct
ssmith$ /opt/python-svn/bin/python mpbug.py -m
Got 'p' of 

This occurs in both 2.6b3 and trunk.

--
components: Library (Lib)
messages: 72662
nosy: TarkaSteve
severity: normal
status: open
title: Module variable overridden in child processes with multiprocessing
type: behavior
versions: Python 2.6

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[issue3792] Module variable overridden in child processes with multiprocessing

[Steve Smith]

Steve Smith <[EMAIL PROTECTED]> added the comment:

Ugh, sorry.  Stupidity on the reporter's part.

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[issue3831] Multiprocessing: Expose underlying pipe in queues

[Steve Smith]

New submission from Steve Smith <[EMAIL PROTECTED]>:

Both Connection and Pipe objects expose their underlying file
descriptors, which is useful for accessing them in an event-driven
manner.  However the higher-level Queue does not make the underlying
pipe available; to get at them you must access private member attributes
which is fragile.  It would be good to have a well-defined API for
accessing either the pipe objects or the underlying FDs.

--
components: Extension Modules
messages: 73001
nosy: TarkaSteve
severity: normal
status: open
title: Multiprocessing: Expose underlying pipe in queues
type: feature request
versions: Python 2.6

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[issue3831] Multiprocessing: Expose underlying pipe in queues

[Steve Smith]

Steve Smith <[EMAIL PROTECTED]> added the comment:

Hi Jesse,

The use-case I had is mind is enabling asyncronous (i.e. select() style)
notification of data being available on the queue, which is more elegant
(and efficient) than polling with get().  Example code showing how this
works with GTK is available here:

http://haltcondition.net/?p=2319

I understand wanting to keep the API simple, however the underlying
posix-level file-descriptors for pipes and connections are already
exposed via fileno(); the actual API change would just be a matter of
changing '_reader' and '_writer' to 'reader' and 'writer' (implicitly
guaranteeing their consistency).

Would it help if I attached a patch showing the proposed change to the
module?  I realise the API is frozen now but it would be nice to have
this further down the line.

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