Re: cpu hotplug oops on 2.6.15-rc5

[Anton Blanchard <anton@samba.org>]

Hi Manfred,

> Very odd call chain.
> Could you enable slab debugging?

Sonny and I had a look around, it seems to be in the
cpuup_callback() / CPU_DEAD case:

      if (!cpus_empty(mask)) {
              spin_unlock(&l3->list_lock);
              goto unlock_cache;
      }

      if (l3->shared) {
              free_block(cachep, l3->shared->entry,
                              l3->shared->avail, node);
              kfree(l3->shared);                <-------- HERE
              l3->shared = NULL;
      }

So we are removing the last cpu in a node, and tearing down the node
related structures. We looked at kfree() -> __cache_free() and we couldnt
convince ourselves that all the CONFIG_NUMA stuff in there wouldnt trip
over itself (since we would be doing the free on an alien node).

Anton