----- "Mike Snitzer" <snitzer@xxxxxxxxx> wrote:
> On Thu, Oct 16, 2008 at 12:25 PM, Dave Anderson <anderson@xxxxxxxxxx>
> wrote:
> >
> > ----- "Mike Snitzer" <snitzer@xxxxxxxxx> wrote:
> >
> >> I'm getting a core when I try to show slab data (kmem -[sS]) on
> >> 2.6.25.17 with both a live crash or saved vmcore.
> >>
> >> The core shows that the segv is coming from memset() via
> >> gather_cpudata_list_v2_nodes (memory.c:10119). This is with crash
> >> 4.0-7.4, but the same crash occurs with crash 4.0-6.3
> >> (memory.c:10108)
> >> and older.
> >>
> >> I've also seen kmem -[sS] segfaults with older kernels too (e.g.
> >> 2.6.22.x).
> >>
> >> Have others experienced this? Would it be useful for me to
> provide
> >> my
> >> kernel config?
> >
> > No that won't help.
>
> Actually I think it may considering kmem -[sS] works perfectly fine
> on
> the same identical 2.6.22.19 kernel if various debug features are
> _not_ enabled, see the attached .config diff. Of note:
> -# CONFIG_DEBUG_SLAB is not set
> +CONFIG_DEBUG_SLAB=y
> +CONFIG_DEBUG_SLAB_LEAK=y
>
> Comparable debug features are enabled in my 2.6.25 kernel that causes
> crash to segfault.
Good point...
>
> > It's failing in the BZERO() here:
> >
> > 10117 for (i = 0; (i < ARRAY_LENGTH(kmem_cache_s_array))
> &&
> > 10118 (cpudata[i]) && !(index); i++) {
> > 10119 BZERO(si->cpudata[i], sizeof(ulong) *
> vt->kmem_max_limit);
> >
> > What is "i" equal to when it segfaults? If you have a crash core
> file,
> > print out the contents of the global "vm_table". In that structure
> > there is a "kmem_max_cpus" field. If "i" is greater or equal to
> that,
> > then that's one explanation.
>
> i=0 and kmem_max_cpus=4.
Ok, then I can't see off-hand why it would segfault. Prior to this
routine running, si->cpudata[0...i] all get allocated buffers equal
to the size that's being BZERO'd.
Is si->cpudata[i] NULL or something?
Dave
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