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

From: Dave Jones
Date: Thu Jan 23 2014 - 17:31:59 EST

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..

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.


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