Re: [PATCH] numa, mem-hotplug: Fix stack overflow in numa whenseting kernel nodes to unhotpluggable.

[Dave Jones]

On Thu, Jan 23, 2014 at 01:58:24AM -0500, Dave Jones wrote:

 > 128 bytes is a pretty small amount of stack though, so I'm just as confused
 > as to what the actual bug here is.
 > 
 > After trying the proposed fix, I got another oops in the early init code..
 > 
 > <trace>
 > nr_free_zone_pages
 > nr_free_pagecache_pages
 > build_all_zonelists
 > start_kernel
 > <rip> ffffffffbc164b1e next_zones_zonelist
 > <rsp> ffffffffbcc01f00

Ok, this is crashing here in next_zones_zonelist...

                while (zonelist_zone_idx(z) > highest_zoneidx)
  de:   3b 77 08                cmp    0x8(%rdi),%esi


I stuck this at the top of the function..

printk(KERN_ERR "z:%p nodes:%p highest:%d\n", z, nodes, highest_zoneidx);

and got

z: 1d08   nodes: (null)  highest:3


Some build tests show..

MAXSMP ( NODESHIFT=10 ) : Bug
NRCPUS=4 & NODESHIFT=10 : Bug
NRCPUS=4 & NODESHIFT=1 : no bug


The middle config test was accidental, I hadn't realised disabling MAXSMP
wouldn't reset NODESHIFT to something sane.

I'll start bisecting, as MAXSMP worked fine until a few days ago.

	Dave

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