On 16-Jul-2002 Andrew Gallatin wrote:
> John Baldwin writes:
>  > > 
>  > > So its still stuck in msleep.   How is it supposed to get back to
>  > > the panic'ed thread if a system thread wakes up and is not allowed to
>  > > go back to sleep???
>  > 
>  > Hmmmmm.  Surprised we don't see this on other archs then (or maybe
>  > we do...).  Probably when we have panic'd (and after we leave the
>  > debugger and go into boot() or some such) we should take any non-P_SYSTEM
>  > processes off the run queues and then remove the panicstr checks from
>  > msleep() and the condition variable wait functions.
> Do you have something like the following psuedo code in mind?
> Perhaps placed just prior to the call to boot() in panic()?
> foreach  p in (all procs in system) {
>     if (p == curproc)
>        continue
>     if (p->p_flag & P_SYSTEM)
>        continue;
>     foreach td in (all threads in p)
>       if (td->td_state == TDS_RUNQ)
>          remrunqueue(td);
> }
> I assume a panic will IPI other processors and halt them in their
> tracks so we don't need to worry too much about locking?

Hmm, it doesn't atm.  Debugger() does, but panic doesn't.

>  > Perhaps better is to dink around in choosethread() so that if panicstr
>  > is set, we throw away any threads get that aren't P_SYSTEM or have the
>  > TDF_INPANIC flag set.  By throw away, I mean that we just ignore any such
>  > threads and loop if we get one we want to throw away.
> I think that I like your first idea better..

I like my second, it is easier, just add this to choosethread:

        if (panicstr &&
            ((td->td_proc->p_flag & P_SYSTEM) == 0 &&
            (td->td_flags & TDF_INPANIC) == 0))
                goto top;

(Do this just before the td_state change and return()).

You of couse need to set TDF_INPANIC when setting panicstr.  This
might mean that we break the restartable panics case.  In that
case you would just change this so that runq_choose() actually does
the work to ignore threads on the run queue instead which eliminates
the loop and ugly goto and preserves the runqueue state in the core

> Drew


John Baldwin <[EMAIL PROTECTED]>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve!"  -  http://www.FreeBSD.org/

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