On Mar 17, 2010, at 9:30 AM, Tim Arnold wrote:
Hi,
I'm checking to see if multiprocessing works on freebsd for any
version of python. My server is about to get upgraded from 6.3 to 8.0
and I'd sure like to be able to use multiprocessing.
I think the minimal test would be:
---------------------
import multiprocessing
q = multiprocessing.Queue()
---------------------
with 6.3, I get
File "/usr/local/lib/python2.6/multiprocessing/__init__.py", line
212, in Queue
from multiprocessing.queues import Queue
File "/usr/local/lib/python2.6/multiprocessing/queues.py", line 22,
in <module>
from multiprocessing.synchronize import Lock, BoundedSemaphore,
Semaphore, Condition
File "/usr/local/lib/python2.6/multiprocessing/synchronize.py", line
33, in <module>
" function, see issue 3770.")
ImportError: This platform lacks a functioning sem_open
implementation, therefore, the required synchronization primitives
needed will not function, see issue 3770.
Hi Tim,
Under FreeBSD 8/Python 2.6.2 I get the same result, unfortunately.
That's a pity because sem_open works under FreeBSD >= 7.2 as we
discussed before.
Issue 3770 is closed with the note, "we've removed hard-coded platform
variables for a better autoconf approach." I'm using the Python built
from FreeBSD's ports, and the note makes me think that it's possible
that if I built my own Python from the Python.org tarball rather than
ports the problem would go away due to autoconf magic. I don't have
the time to offer to do this for you, unfortunately. But why not
install FreeBSD 8 under VirtualBox or somesuch and give it a go
yourself?
A couple of quirks I noted related to FreeBSD & POSIX IPC that you
might find useful --
- The sem and mqueuefs kernel modules must be loaded, otherwise you'll
get a message like this when you try to create a semaphore or message
queue:
Bad system call: 12 (core dumped)
Under 8.0 they're loaded by default, I think.
- C apps that want to use message queues must link to the realtime
libs (pass -lrt to the linker). This tripped me up for a while.
Linking to the realtime libs is required for all POSIX IPC calls under
Linux; FreeBSD does not require it for semaphores or shared mem, only
message queues.
Hope this helps
Philip
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