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

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Date:	Tue, 28 Jan 2014 13:17:21 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	Dave Jones <davej@...hat.com>,
	David Rientjes <rientjes@...gle.com>, tglx@...utronix.de,
	mingo@...hat.com, hpa@...or.com, akpm@...ux-foundation.org,
	zhangyanfei@...fujitsu.com, guz.fnst@...fujitsu.com,
	x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] numa, mem-hotplug: Fix stack overflow in numa when seting
 kernel nodes to unhotpluggable.

On 01/28/2014 12:47 PM, Dave Jones wrote:
> On Tue, Jan 28, 2014 at 12:47:11PM +0800, Tang Chen wrote:
>   >  On 01/28/2014 11:55 AM, Dave Jones wrote:
>   >  >  On Tue, Jan 28, 2014 at 11:24:37AM +0800, Tang Chen wrote:
>   >  >
>   >  >    >   >   I did a bisect with the patch above applied each step of the way.
>   >  >    >   >   This time I got a plausible looking result....
>   >  >    >
>   >  >    >   I cannot reproduce this. Would you please share how to reproduce it ?
>   >  >    >   Or does it just happen during the booting ?
>   >  >
>   >  >  Just during boot. Very early. So early in fact, I have no logging facilities
>   >  >  like usb-serial, just what is on vga console.
>   >  >
>   >  >  If you want me to add some printk's, I can add a while (1); before
>   >  >  the part that oopses so we can diagnose further..
>   >
>   >  Sure. Would you please do that for me ? Maybe we can find something in
>   >  the early log.
>
> I was hoping you'd have suggestions what you'd like me to dump ;-)

Sorry. I didn't say it clearly. :)

Seeing from your earlier mail, it crashed at:

                 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


nodes=null and highest=3, they are correct. When looking into 
next_zones_zonelist(),
I cannot see why it crashed. So, can you print the zone id in the
for_each_zone_zonelist() loop in nr_free_zone_pages() ?

I want to know why it crashed. A NULL pointer ?  Which one ?

Thanks.

>
> 	Dave
>
>
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