[Python-ideas] An error in multiprocessing on MacOSX?

[Richard Oudkerk]

On 21/11/2012 8:29pm, Gregory P. Smith wrote:
> I don't care how this is read or what the default behavior is. All I
> want is for someone who cares about multiprocessing actually working
> well for people to implement optional support for *not* using os.fork()
> on posixish systems.  ie: port an equivalent of the windows stuff over.
>
> I don't use multiprocessing so I've never looked into adding it.  It
> shouldn't be difficult given the legwork has already been done for use
> on windows.  this is exactly what issue8713 is asking for.

An implementation is available at

     http://hg.python.org/sandbox/sbt#spawn

You just need to stick

     multiprocessing.set_start_method('spawn')

at the beginning of the program to use fork+exec instead of fork.  The 
test suite passes.  (I would not say that making this work was that 
straightforward though.)

That branch also supports the starting of processes via a server 
process.  That gives an alternative solution to the problem of mixing 
fork() with threads, but has the advantage of being as fast as the 
default fork start method.  However, it does not work on systems where 
fd passing is unsupported like OpenSolaris.

-- 
Richard