[Crash-utility] kmem -[sS] segfault on 2.6.25.17

[Dave Anderson]

----- "Mike Snitzer" <snitzer at gmail.com> 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. 

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.

Or you can bring up the dumpfile (or live system), and look at the value 
kmem_max_cpus by looking at the output of "help -v". 

Dave


Dave