RE: Looks like a bug to me... in 2.4 series

Good point, Martin

The fs and gs registers have always been poorly handled in any process
migration system, because their use is ambiguous from the kernel side. 

So what are you proposing it should be written as?

moshe 

-----Original Message-----
From: openmosix-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
[mailto:openmosix-devel-admin-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org] On Behalf Of Martin Guy
Sent: Friday, February 10, 2006 11:07 AM
To: openmosix-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org
Subject: [Openmosix-devel] Looks like a bug to me... in 2.4 series

Hi folks
   I've been trying to put OM into the current debian 2.4 kernel and
browsing the patches I am worried by the following code fragments in
openMosix-2.4.26-2 and its derivatives.

Watch the use of altfs/altgs

+++ hpc/mig.c
        /* restore segment registers.
           FIXME: do this only if remote modified LDT */
        loadsegment(gs, m->altgs);
        loadsegment(fs, m->altgs);

+++ hpc/service.c
        /* load segment registers
           FIXME: do this only if remote modified LDT */
        loadsegment(gs, p->mosix.altgs);
        loadsegment(fs, p->mosix.altfs); ...then later...
        /* load segment registers
           FIXME: do this only if remote modified LDT */
        loadsegment(gs, p->mosix.altgs);
        loadsegment(fs, p->mosix.altgs);

Does anyone know whether these are typoes from when the lines were copied
and pasted, or should altgs really be used for both fs and gs? Up until
2.4.24-2, it's always "altgs" in both places, then in 2.4.26-1 it appears as
above: fs, altfs in one place only.

My symptoms are that simple tasks (infinite loops) distribute and run ok,
but complex ones get occational segfaults and other times the kernel gets a
NULL pointer dereference and hangs.

Any ideas?

    M


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