Panic "Fatal trap 18: integer divide fault while in kernel mode"

[Jung-uk Kim]

On Thursday 30 April 2009 12:37 pm, pluknet wrote:
> 2009/4/30 Andriy Gapon <avg at icyb.net.ua>:
> > on 30/04/2009 18:58 David Wolfskill said the following:
> >> On Thu, Apr 30, 2009 at 06:35:32PM +0300, Andriy Gapon wrote:
> >>> on 30/04/2009 18:18 David Wolfskill said the following:
> >>>> On Wed, Apr 29, 2009 at 09:16:26AM -0700, David Wolfskill 
wrote:
> >>>>> Is there anything of use I might get from DDB?
> >>>>
> >>>> I can still poke around there for a bit, if that would be
> >>>> useful.
> >>>
> >>> In general the stack trace[*] should be provided at the very
> >>> least, otherwise people have hard figuring out where the
> >>> problem occurred, so right people may just not notice a report.
> >>
> >> Sorry; it happened so quickly, I wasn't at all certain there
> >> would be enough to show:
> >>
> >> db> bt
> >> Tracing pid 0 tid 100000 td 0xc0d43610
> >> cpu_topo(2,c1420d34,c081ff07,c1420d58,c0820042,...) at
> >> cpu_topo+0x43 smp_topo(c0804378,2,c4145a5c,fffffff,0,...) at
> >> smp_topo+0x10b
> >> sched_setup(0,141ec00,141ec00,141e000,1425000,...) at
> >> sched_setup+0x1a mi_startup() at mi_startup+0x96
> >> begin() at begin+0x2c
> >
> > My guess is that (cpu_cores * cpu_logical) somehow equals to
> > zero.
>
> That was masked earlier by  additional checks on zero,
> and now that routine moved to the separate function
> (and to separate call path from subr_smp.c:mp_start()
> which seems not to be called).
>
> > Have you by a chance saved this crash dump?
> > I think that t would be interesting to look at it in kgdb.

Please try the attached patch.

Jung-uk Kim
-------------- next part --------------
--- sys/amd64/amd64/mp_machdep.c	(revision 191699)
+++ sys/amd64/amd64/mp_machdep.c	(working copy)
@@ -214,6 +214,8 @@
 		else if (type == CPUID_TYPE_CORE)
 			cpu_cores = cnt;
 	}
+	if (cpu_cores == 0)
+		cpu_cores = 1;
 	if (cpu_logical == 0)
 		cpu_logical = 1;
 	cpu_cores /= cpu_logical;
--- sys/i386/i386/mp_machdep.c	(revision 191699)
+++ sys/i386/i386/mp_machdep.c	(working copy)
@@ -267,6 +267,8 @@
 		else if (type == CPUID_TYPE_CORE)
 			cpu_cores = cnt;
 	}
+	if (cpu_cores == 0)
+		cpu_cores = 1;
 	if (cpu_logical == 0)
 		cpu_logical = 1;
 	cpu_cores /= cpu_logical;