Re: POSIX.1 semaphores vs message queues

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

On Sun, Nov 08, 2015 at 06:35:36AM +0800, Paul Goyette wrote:
> On Sat, 7 Nov 2015, Joerg Sonnenberger wrote:
> 
> >On Sat, Nov 07, 2015 at 10:55:49AM +0800, Paul Goyette wrote:
> >>I'd like to understand the rationale that makes POSIX sempahores a
> >>non-optional component of the kernel, while POSIX message queues are
> >>still optional.  Both seem to be related specifically to use in the
> >>librt real-time library.
> >
> >Semaphores are used quite a lot and not only required by librt, but
> >also by libpthread. I'm not sure what is using message queues.
> 
> Hmmm, sounds like a great reason to include the semaphore code in
> every kernel by default.  But it doesn't sound sufficiently critical
> to _prevent_ it from being removed from custom kernels if explicitly
> requested by the user.
> 
> I'd like to suggest that this code once again become an option.  Rather
> than adding an option to every kernel configuration file, however, we
> can simply add it to src/sys/conf/std where it will get included by
> default, in the same manner as MQUEUE.  (I also propose use of "option
> SEMAPHORE" rather than P1003_1B_SEMAPHORE, similar to MQUEUE.)

I don't see the point in having options for every single system call or
the like. At best, it is a form of modularity masturbation and at worst,
it is asking for difficult to analyze bugs when someone actually insists
on removing them.

Joerg