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Re: Please read if you use x86 -current

On Wed, Nov 12, 2008 at 02:57:08PM +0000, Andrew Doran wrote:
 > The first component to be moved is POSIX semaphores. The GENERIC kernel no
 > longer has the P1003_1B_SEMAPHORE option. If POSIX semaphores are used, the
 > ksem kernel module will be automatically loaded. The same will happen for
 > compat code and other facilities as time goes by.

So, what do you do if you want a system entirely without POSIX
semaphores? It looks as if you have to patch the source to avoid
building the module.

This is not particularly important for POSIX semaphores, but there are
other cases where it does matter to many people, and I think patching
the source tree is not really the right answer.

 > The change means that from now on, those running current+GENERIC on the i386
 > or amd64 ports need up-to-date modules installed. So if you are on 5.99.01,
 > you need kernel modules built and installed for that version under, say,
 > /stand/i386/5.99.01/modules. To build and install modules:
 >      cd src/sys/modules
 >      make
 >      make install

I don't think this is all that great an idea either, because it means
you have to know, every time you build a new kernel, if there's been a
version bump or not *before* you boot it. Otherwise, you can all too
easily end up in a situation where you have a broken new kernel and
have overwritten the modules that correspond to your old kernel...
which might leave you wedged. Again, probably not with POSIX
semaphores, but there are plenty of other cases that may matter.

 > I am open to ideas about how this can be automated either via the kernel
 > makefile, or

I think if we're going to move in this direction (which FWIW I
continue to think is a bad idea) it needs to be worked into config.

We need also stronger guards against, and a stronger recovery
mechanism for, accidental breakage of module compat without a
corresponding version bump.

David A. Holland

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