Re: fairsched + O(1) process scheduler

[Antonio Vargas <wind@cocodriloo.com>]

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