Fatal trap 18

[Sergey Kandaurov]

On 3 November 2010 08:30, Dan Allen <danallen46 at airwired.net> wrote:
> FreeBSD 8.1-STABLE sometime after 10/28/2010 has caused a fatal boot error on my Toshiba U205, 1.8 GHz Core Duo laptop.
>
> Many times every week I sync with STABLE and build everything.  I have been doing this for years.
>
> I sync'd (via csup) and built on 10/28/2010 and everything was fine.
>
> Then I sync'd yesterday 11/1/2010 and it crashes on boot.  The diagnostics print out the following:
>
> ---
>
> Fatal trap 18: integer divide fault while in kernel mode
>
> kdb_backtrace
> panic
> trap_fatal
> trap
> calltrap
> topo_probe
> cpu_topo
> smp_topo
> sched_setup
> mi_startup
>
> ---
>
> I reverted at the loader via boot /boot/kernel.old, resync'd today, rebuilt, and things are still broken.
>

It's possible in theory to leave cpu_logical as zero in topo_probe_0x4().
So, it makes sense to add some sort of the check.

Index: svn/freebsd/head/sys/amd64/amd64/mp_machdep.c
===================================================================
--- svn/freebsd/head/sys/amd64/amd64/mp_machdep.c       (revision 214725)
+++ svn/freebsd/head/sys/amd64/amd64/mp_machdep.c       (working copy)
@@ -239,6 +239,8 @@
                        cpu_logical++;
        }

+       if (cpu_logical == 0)
+               cpu_logical = 1;        /* XXX max_logical? */
        cpu_cores /= cpu_logical;
        hyperthreading_cpus = cpu_logical;
 }


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