[Python-Dev] Forking and Multithreading - enemy brothers

[Pascal Chambon]

Hello

Some update about the spawnl() thingy ;

I've adapted the win32 code to have a new unix Popen object, which works 
with a spawn() semantic. It's quite straightforward, and the 
mutiprocessing call of a python functions works OK.

But I've run into some trouble : synchronization primitives.
Win32 semaphore can be "teleported" to another process via the 
DuplicateHandle() call. But unix named semaphores don't work that way - 
instead, they must be opened with the same name by each spawned subprocess.
The problem here, the current semaphore C code is optimized to forbid 
semaphore sharing (other than via fork) : use of (O_EXL|O_CREAT) on 
opening, immediate unlinking of new semaphores....

So if we want to benefit from sync primitives with this spawn() 
implementation, we need a working named semaphore implementation, too...

What's the best in your opinion ? Editing the current multiprocessing 
semaphore's behaviour to allow (with specific options, attributes and 
methods) its use in this case ? Or adding a new NamedSemaphore type like 
this one ?
http://semanchuk.com/philip/posix_ipc/

Regards,
Pascal

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