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RE: [Xen-devel] segfault in VM

  • To: <xen-devel@xxxxxxxxxxxxxxxxxxxxx>
  • From: James Harper <JamesH@xxxxxxxxxxxxxxxx>
  • Date: Tue, 20 Jul 2004 11:04:22 +1000
  • Delivery-date: Tue, 20 Jul 2004 02:06:38 +0100
  • List-id: List for Xen developers <xen-devel.lists.sourceforge.net>
  • Thread-index: AcRt7K8lsSLq91byQwyEO39w3ZgetgACM7Qb
  • Thread-topic: [Xen-devel] segfault in VM

bk pull only showed 2 patches, neither of which affected kernels so I didn't bother recompiling.
I have seen an error (shown by my diff script 'compare' or by xend doing silly things like crashing), by simply starting another domain and pinging it with something like:
ping -s 1400 -i 0.001
(ping -f might do it but I think it goes a bit fast)
That occured once after about 5 minutes, but then not again for the 10 or so minutes I left it running.
running it out of memory with this code:
#include <stdio.h>
#include <stdlib.h>
int main() {
        char *buf;
        int mem = 0;
        int size = 1;
        char rnd;
        rnd = rand() & 255;
        while(1) {
                buf = (char *)malloc(size*1024*1024);
                memset(buf, rnd, size*1024*1024);
                if (buf != NULL) {
                        mem += size;
                        printf("%d\n", mem);
causes a crash far more quickly. I guess it's possible that those are two different errors though...

From: James Harper
Sent: Tue 20/07/2004 10:01 AM
To: Derek Glidden; xen-devel@xxxxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-devel] segfault in VM

I'm pretty sure i've seen it earlier than that, but couldn't be certain. Initially I more or less expected instabilities and so wasn't really taking much notice.
so I guess my comments above are of absolutely no help at all. :)
i'll be trying a bk pull and build today (under normal linux - 2 cpus and max memory = faster builds) then verify that i can still make it crash, then try nosmp, although i've seen a few posts about single cpu crashes.

From: Derek Glidden
Sent: Tue 20/07/2004 5:06 AM
To: xen-devel@xxxxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] segfault in VM

On Jul 19, 2004, at 9:22 AM, Keir Fraser wrote:
> The first person to complain I think was Jody Belka, who was using
> the changeset with comment 'Fairly major fixes to the network frontend
> driver...' (2004-07-13 18:24:48). Perhaps backing off to a day before
> that would be a sensible place to start?

I'm either going to blow your theory out of the water or help a lot 
because my first "real" build of all the Xen tools & kernel & linux 
kernels where I actually booted into a dom0 kernel from Xen was from a 
checkout on either the 12th or 13th.  Prior to that I was working out 
getting everything built under gentoo and not actually running it.  And 
that's what I've been using until I checked out and rebuilt everything 
fresh this sunday afternoon and still have the problem as of last 
night.  Although a VM will segfault while dom0 seems to panic, it's 
probably the same root problem.

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