Panic on -CURRENT after LDT changes

Attilio Rao attilio at freebsd.org
Fri May 25 18:35:23 UTC 2007


2007/5/25, Joe Marcus Clarke <marcus at marcuscom.com>:
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> Attilio Rao wrote:
> > 2007/5/25, Joe Marcus Clarke <marcus at marcuscom.com>:
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> >> Attilio Rao wrote:
> >> > 2007/5/24, Joe Marcus Clarke <marcus at marcuscom.com>:
> >> >> On Thu, 2007-05-24 at 20:13 +0200, Attilio Rao wrote:
> >> >> > Jeff Roberson wrote:
> >> >> > > Thanks,  Attilio and I will look at this right away.
> >> >> > >
> >> >> > > Jeff
> >> >> > >
> >> >> > > On Wed, 23 May 2007, Joe Marcus Clarke wrote:
> >> >> > >
> >> >> > >> On a -CURRENT build today with Jeff's LDT locking changes, I
> >> get an
> >> >> > >> instant, reproducible panic by doing:
> >> >> > >>
> >> >> > >> # cd /usr/src
> >> >> > >> # make -DNO_CLEAN buildworld
> >> >> > >>
> >> >> > >> Backing out the LDT changes to /sys/i386/i386/*machdep*
> >> corrects the
> >> >> > >> problem.  Here is a dmesg and backtrace.  In frame 6, it appears
> >> >> mdp is
> >> >> > >> NULL (i.e. td->td_proc->p_md = 0x0).
> >> >> >
> >> >> > Did you enable WITNESS/INVARIANTS/INVARIANT_SUPPORT?
> >> >>
> >> >> No, this kernel does not have WITNESS or INVARIANTS.  I can enable
> >> those
> >> >> tomorrow if that would give you more useful information.
> >> >
> >> > It would be very appreciated, since I've been unable to reproduce your
> >> > panic on a centrino dual core.
> >>
> >> I'm stopped in the debugger now with WITNESS and friends enabled.  Same
> >> backtrace as before.  I did a "show locks" and I see:
> >>
> >> exclusive spin mutex descriptor tables r = 0 (0xc08369f8) locked @
> >> /usr/src/sys/i386/i386/sys_machdep.c:629
> >>
> >> Please let me know what else you'd like to see while I'm at the
> >> debugger.  FYI: this is a Pentium 4 with "options SMP" disabled.
> >
> > This is a multicore? do you have PREEMPTION/FULL_PREEMPTION installed?
>
> No, single core with PREEMPTION enabled only.

Very strange.
Could you disable PREEMPTION and see if the error persists?

Thanks,
Attilio


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