Re: Scheduler broken on VAX?

[Anders Magnusson <ragge%ludd.ltu.se@localhost>]

Johnny Billquist wrote:
> George Harvey wrote:
> > Tested on 5.0_RC2 running on a 4000/500A...
> >
> > There was a thread a few weeks ago about system hangs and how breaking
> > into ddb and single stepping for a while would un-hang them. I've now
> > found a simple way to reproduce the symptoms: just run a program with an
> > infinite loop in it, other terminal sessions will stop responding but
> > the box will still respond to pings. This looks like the scheduler is
> > being locked out somehow but I'm unfamiliar with the kernel internals so
> > I'm hoping someone more knowledgeable might have some suggestions.
>
> Excellent with such a short program to reproduce the problem.
> Now someone just needs to spend some time figuring out what the 
> problem is.
Rescheduling on vax isn't difficult.  If the machine finds out at a 
timer interrupt that
the current process should be preempted, it sets the cpu-specific flag 
ci_want_resched
and posts an AST.  When the AST is received (in user space) a trap will 
occur that
calls userret(), checks for ci_want_resched and calls preempt().

The code looks sane to me.

-- Ragge