Bugs item #1753891, was opened at 2007-07-14 03:06
Message generated for change (Settings changed) made by gbrandl
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Category: Threads
Group: Python 2.4
>Status: Closed
Resolution: Duplicate
Priority: 5
Private: No
Submitted By: slowfood (slowfood)
Assigned to: Nobody/Anonymous (nobody)
Summary: subprocess raising "No Child Process" OSError
Initial Comment:
The program below demostrates a "No Child Process" OSError on a multi-cpu
systems.
This is extracted from a large system where we
are trying to manage many sub-processes,
some of which end up having little/no real work to
do so they return very fast, here emulated by
having the sub-process be an invocation of:
Executable="/bin/sleep 0"
Seems like some race condition, since if you make the
child process take some time (sleep 0.1) the frequency
of errors decreeses.
Error only shows up when there are more threads than
have real CPU's by at least a factor of two, on dual core machines up
NumThreads to 18 to get the failures.
Same error on both Python 2.4.3 with:
Linux 2.6.18-gentoo-r3 Gentoo
and Python 2.4.4 with:
Linux 2.6.20-gentoo-r8
Any help appreciated -
= = = ===== Start code example ===========
% python subprocess_noChildErr.py
Exception in thread Thread-3:
Traceback (most recent call last):
File "/usr/lib64/python2.4/threading.py", line 442, in __bootstrap
self.run()
File "testCaseA.py", line 14, in run
subprocess.call(Executable.split())
File "/usr/lib64/python2.4/subprocess.py", line 413, in call
return Popen(*args, **kwargs).wait()
File "/usr/lib64/python2.4/subprocess.py", line 1007, in wait
pid, sts = os.waitpid(self.pid, 0)
OSError: [Errno 10] No child processes
Test finished
% cat subprocess_noChildErr.py
import subprocess, threading
# Params
Executable="/bin/sleep 0"
NumThreads = 18
NumIterations = 10
class TestClass(threading.Thread):
def __init__(self, threadNum):
self.threadNum = threadNum
threading.Thread.__init__(self)
def run(self):
for i in range(NumIterations):
subprocess.call(Executable.split())
def test():
allThreads = []
for i in range(NumThreads):
allThreads.append(TestClass(i))
for i in range(NumThreads):
allThreads[i].start()
for i in range(NumThreads):
allThreads[i].join()
print "Test finished"
if __name__ == '__main__':
test()
% python -V
Python 2.4.4
% uname -a
Linux 2.6.20-gentoo-r8 #2 SMP PREEMPT Sun Jul 1 13:22:56 PDT 2007 x86_64
Dual-Core AMD Opteron(tm) Processor 2212 AuthenticAMD GNU/Linux
%
% date
Fri Jul 13 19:26:44 PDT 2007
%
= = = ===== End code example ===========
----------------------------------------------------------------------
Comment By: Georg Brandl (gbrandl)
Date: 2007-08-04 07:25
Message:
Logged In: YES
user_id=849994
Originator: NO
Closing too. Tying bugs is not supported by SF.
----------------------------------------------------------------------
Comment By: slowfood (slowfood)
Date: 2007-08-03 20:07
Message:
Logged In: YES
user_id=1844537
Originator: YES
Managed to mark it as a duplicate, but not able to tie it to 1731717.
Sorry -
;;slowfood
----------------------------------------------------------------------
Comment By: slowfood (slowfood)
Date: 2007-08-03 20:01
Message:
Logged In: YES
user_id=1844537
Originator: YES
I agree with abo that this looks to be a dup of 1731717, will try to mark
it as such.
----------------------------------------------------------------------
Comment By: Donovan Baarda (abo)
Date: 2007-08-03 19:37
Message:
Logged In: YES
user_id=10273
Originator: NO
Bugs 1754642 and 1753891 both look like duplicates of bug 1731717 to me. I
suggest marking them both as dups of 1731717 because that one has info on
the race-condition that causes this and discussions on how to fix it.
----------------------------------------------------------------------
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