[Python-Dev] semaphore support in thread_*.h

[Tim Peters]

[David Ascher]
> I noticed that the support for the semaphore calls in the various thread_*
> is very very spotty, with a comment in the BeOS implementation that read:
>
>  * Guido says not to implement this because it's not used anywhere;
>  * I'll do it anyway, you never know when it might be handy, and it's
>  * easy...

> (that last bit is not true of all implementations, apparently =).
>
> 1) Is it true that the sema_ calls are never used?

Best I can tell, the following sema functions are indeed never used:

    PyThread_allocate_sema
    PyThread_free_sema
    PyThread_down_sema
    PyThread_up_sema

the following #define's are never used:

    WAIT_SEMA
    NOWAIT_SEMA

and the following non-sema pythread.h functions are not only never used,
they're defined only in thread_sgi.h:

    PyThread_create_key
    PyThread_delete_key
    PyThread_set_key_value
    PyThread_get_key_value

> 2) If yes, shouldn't we remove the sema_ calls from the thread
> API and have similar functionality on all platforms?

+1 from me.  If someone wants platform-specific thread functions, they
should be in a platform-specific extension module, not messing up the core.

> (There are related issues re: for example whether async thread locking is
> available, whether threads are joinable or not (see
> thread_cthread.h), etc.)

Sorry, don't know what you're getting at here (e.g., have any specific line
or function of thread_cthread.h in mind?).