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SubjectRe: [patch] Real-Time Preemption, -RT-2.6.9-rc4-mm1-U8
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On Thu, Oct 21, 2004 at 10:14:43PM +0200, Jens Axboe wrote:
> On Thu, Oct 21 2004, Bill Huey wrote:
> > A lot of things are perfectly "valid" in the Linux kernel regarding
> > stuff like that are a bit irregular. But the preemption work about
> > to stress these things in ways that was never designed to which is
> > why these patches are needed. Having a clear use of various locking
> > conventions is key to getting this system to behave in a predictable
> > manner. Quite simply, Linux was never targetted to do this and the
> > sloppiness is showing so it's got to be removed.
>
> I have to disagree, I don't think the above use is either convoluted or
> sloppy in any way. Now that we have the completion structure, certain
> things are surely better implemented as such. But the old use is
> perfectly valid and logical, imho.

You use a semaphore to protect data, a completion isn't protecting data
but preserving a certain kind of wait ordering in the code. The
possibility of overloading the current mutex_t for PI makes for a conceptual
mismatch when used in this case since having a kind of priority for
completions is a bit odd. It's better to flat out use a completion
instead, IMO.

bill

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