Re: reboot or shutdown not working with -current

On Fri, 4 Jun 2004, John Baldwin wrote:
> On Friday 04 June 2004 10:51 am, Kenneth Culver wrote:
> > Quoting John Baldwin <jhb_at_FreeBSD.org>:
> > > On Thursday 03 June 2004 11:04 am, Dan Nelson wrote:
> > >> In the last episode (Jun 03), David Gurvich said:
> > >> > Recent cvsup has caused system to hang on reboot or shutdown,
> > >> > occasionally hangs on startup with detection of optical drive on 2nd
> > >> > ide.  Anyone know how to get system logs in this situation?
> > >> > Motherboard is ASUS A7N266-VM.  System worked reasonably with APIC
> > >> > turned off 5/26/2004.
> > >>
> > >> Back out sys/i386/i386/intr_machdep.c rev 1.6.
> > >
> > > Or for the real fix, try this:
> > >
> > > Index: acpi_cpu.c
> > > ===================================================================
> > > RCS file: /usr/cvs/src/sys/dev/acpica/acpi_cpu.c,v
> > > retrieving revision 1.36
> > > diff -u -r1.36 acpi_cpu.c
> > > --- acpi_cpu.c  7 May 2004 05:22:37 -0000       1.36
> > > +++ acpi_cpu.c  4 Jun 2004 14:44:33 -0000
> > > _at__at_ -376,8 +376,7 _at__at_
> > >
> > >      /* Wait for all processors to exit acpi_cpu_idle(). */
> > >      smp_rendezvous(NULL, NULL, NULL, NULL);
> > > -    while (cpu_idle_busy > 0)
> > > -       DELAY(1);
> > > +    DELAY(1);
> > >
> > >      return_VALUE (0);
> > >  }
> >
> > You know that the reboot problems go away when
> > /usr/src/sys/i386/i386/intr_machdep.c is reverted from 1.16 to 1.15 right?
>
> Yes, because the real bug is above.  Disabling interrupt preemption just masks
> it.  The gory details are that almost all (in fact on UP, 100%) of context
> switches away from the idlethread are due to interrupts.  When interrupt
> preemption is enabled, this means that idle threads are switched away from
> before they've had a chance to decrement the cpu_idle_busy counter in
> acpi_cpu_idle().  Thus, when the thread doing shutdown gets to this loop, it
> never terminates because the idlethread of the CPU executing the shutdown
> request never gets a chance to go back and decrement its idle_busy count.  In
> truth, you don't actually need the loop, once you do the rendezvous, any
> other CPUs that are idle will wake up, exit acpi_cpu_idle() and re-enter
> after finding no runnable jobs.  I tracked this down after a couple of hours
> on Wednesday but was very busy with ${REALJOB} work yesterday and haven't had
> a chance to send an e-mail out about this.

I'm swamped too.  Please commit a #if 0 around the while () until I can
get to this.

Thanks,
Nate