[issue15702] Multiprocessing Pool deadlocks on join after empty map operation

[James Hutchison]

New submission from James Hutchison:

Following code deadlocks on Windows 7 64-bit, Python 3.2.3

If you have a pool issue a map operation over an empty iterable then try to join later, it will deadlock. If there is no map operation or blah in the code below isn't empty, it does not deadlock

from multiprocessing import Pool

def main():
    p = Pool();
    blah = [];
    print("Mapping");
    p.map(dummy, blah);
    p.close();
    p.join(); # deadlocks here
    print("Done");

def dummy(x):
    pass;

if __name__ == "__main__":
    main();

----------
components: Library (Lib)
messages: 168408
nosy: Jimbofbx
priority: normal
severity: normal
status: open
title: Multiprocessing Pool deadlocks on join after empty map operation
type: behavior
versions: Python 3.2

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue15702>
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