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Re: POSIX.1 semaphores vs message queues



On Mon, 9 Nov 2015, Joerg Sonnenberger wrote:

On Mon, Nov 09, 2015 at 08:05:43AM +0800, Paul Goyette wrote:
Well, both EXEC_SCRIPT and COREDUMP are modularized, and they _are_
optional.

See part about modularity masturbation. Making things optional for the
sake of making them optional is just as wrong.

Both EXEC_SCRIPT and COREDUMP are also much smaller than the ksem code;
these two optional/removeable modules together add up to just about
the size of a SEMAPHORE module.  (On amd64 we have exec_script weighing
in at 1285 bytes and coredump at 3895 bytes, while ksem tips the scales
at 5186 bytes).  There are numerous other modules which are similar in
size to the SEMAPHORE module.

Add in the page alignment and the cost becomes even larger. There is
nothing to be gained.

The gain is flexibility, for those who may want it.  And possibly
finding (and eventually fixing) latent bugs, either in the semaphore
code itself or in the module system, which can be exposed by making
the code optional and loadable.

We also gain consistency with existing practice, evidenced by the
various examples I've cited.

There is nothing to be lost for anyone who doesn't explicitly remove
the semaphore code from their kernel via 'no options'.



+------------------+--------------------------+-------------------------+
| Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:       |
| (Retired)        | FA29 0E3B 35AF E8AE 6651 | paul at whooppee.com    |
| Kernel Developer | 0786 F758 55DE 53BA 7731 | pgoyette at netbsd.org  |
+------------------+--------------------------+-------------------------+


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