Re: fairsched + O(1) process scheduler

Antonio Vargas (wind@cocodriloo.com)
Thu, 3 Apr 2003 00:07:34 +0200


On Wed, Apr 02, 2003 at 04:35:00PM -0500, Robert Love wrote:
> On Wed, 2003-04-02 at 16:36, Antonio Vargas wrote:
>
> > I've been thinking about this thing a while ago, and I think I could do this:
> >
> > a. Have a kernel thread which wakes up on each tick.
>
> Why not use the timer tick itself? It already calls scheduler_tick()...
>
> Oh, because you need to grab uidhash_lock? Ew. Needing a kernel thread
> for this is not pretty.

Hmmm, we had some way for executing code just after an interrupt,
but outside interrupt scope... was it a bottom half? Can you
point me to some place where it's done?

> > Also, this locking rule means I can't even read current->user->time_slice?
> > What if I changed the type to an atomic_int?
>
> You can always read a single word-sized type atomically. No need for
> atomic_t's.

Ok, I did know m68k can do it, but wasn't sure about all other arches :)

Btw, I'm testing the patch using UML and besides I don't have any SMP
machine, hope any of you can test it when it looks good :)

Greets, Antonio
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