Re: Scheduler broken on VAX?

[Johnny Billquist <bqt%softjar.se@localhost>]

Anders Magnusson wrote:
> 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.

Something is obviously wrong, though. :-)
Maybe the ASTs are being locked out?

        Johnny

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Johnny Billquist                  || "I'm on a bus
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