linux-kernel - Re: WARNING: at mm/page_alloc.c:4514 free_area_init

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Date:	Thu, 2 Aug 2012 13:06:41 +0200
From:	Borislav Petkov <bp@...64.org>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Tejun Heo <tj@...nel.org>, Ralf Baechle <ralf@...ux-mips.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: WARNING: at mm/page_alloc.c:4514 free_area_init_node+0x4f/0x37b()

On Thu, Aug 02, 2012 at 08:33:35AM +0900, Minchan Kim wrote:
> Hello Borislav,
> 
> On Wed, Aug 01, 2012 at 07:38:37PM +0200, Borislav Petkov wrote:
> > Hi,
> > 
> > I'm hitting the WARN_ON in $Subject with latest linus:
> > v3.5-8833-g2d534926205d on a 4-node AMD system. As it looks from
> > dmesg, it is happening on node 0, 1 and 2 but not on 3. Probably the
> > pgdat->nr_zones thing but I'll have to add more dbg code to be sure.
> 
> As I look the code quickly, free_area_init_node initializes node_id and
> node_start_pfn doublely. They were initialized by setup_node_data.
> 
> Could you test below patch? It's not a totally right way to fix it but
> I want to confirm why it happens.
> 
> (I'm on vacation now so please understand that it hard to reach me)

I sincerely hope you're not going to interrupt your vacation because of
this.

:-).

> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 889532b..009ac28 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4511,7 +4511,7 @@ void __paginginit free_area_init_node(int nid, unsigned long *zones_size,
>         pg_data_t *pgdat = NODE_DATA(nid);
>  
>         /* pg_data_t should be reset to zero when it's allocated */
> -       WARN_ON(pgdat->nr_zones || pgdat->node_start_pfn || pgdat->classzone_idx);
> +       WARN_ON(pgdat->nr_zones || pgdat->classzone_idx);
>  
>         pgdat->node_id = nid;
>         pgdat->node_start_pfn = node_start_pfn;

Yep, you were right: ->node_start_pfn is set. I added additional debug
output for more info:

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 889532b8e6c1..c249abe4fee2 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4511,7 +4511,17 @@ void __paginginit free_area_init_node(int nid, unsigned long *zones_size,
        pg_data_t *pgdat = NODE_DATA(nid);
 
        /* pg_data_t should be reset to zero when it's allocated */
-       WARN_ON(pgdat->nr_zones || pgdat->node_start_pfn || pgdat->classzone_idx);
+       WARN_ON(pgdat->nr_zones || pgdat->classzone_idx);
+
+       if (pgdat->node_start_pfn)
+               pr_warn("%s: pgdat->node_start_pfn: %lu\n", __func__, pgdat->node_start_pfn);
+
+       if (pgdat->nr_zones)
+               pr_warn("%s: pgdat->nr_zones: %d\n", __func__, pgdat->nr_zones);
+
+       if (pgdat->classzone_idx)
+               pr_warn("%s: pgdat->classzone_idx: %d\n", __func__, pgdat->classzone_idx);
+
 
        pgdat->node_id = nid;
        pgdat->node_start_pfn = node_start_pfn;



Here's what it says:

[    0.000000] On node 0 totalpages: 4193848
[    0.000000]   DMA zone: 64 pages used for memmap
[    0.000000]   DMA zone: 6 pages reserved
[    0.000000]   DMA zone: 3890 pages, LIFO batch:0
[    0.000000]   DMA32 zone: 16320 pages used for memmap
[    0.000000]   DMA32 zone: 798464 pages, LIFO batch:31
[    0.000000]   Normal zone: 52736 pages used for memmap
[    0.000000]   Normal zone: 3322368 pages, LIFO batch:31
[    0.000000] free_area_init_node: pgdat->node_start_pfn: 4423680	<----
[    0.000000] On node 1 totalpages: 4194304
[    0.000000]   Normal zone: 65536 pages used for memmap
[    0.000000]   Normal zone: 4128768 pages, LIFO batch:31
[    0.000000] free_area_init_node: pgdat->node_start_pfn: 8617984	<----
[    0.000000] On node 2 totalpages: 4194304
[    0.000000]   Normal zone: 65536 pages used for memmap
[    0.000000]   Normal zone: 4128768 pages, LIFO batch:31
[    0.000000] free_area_init_node: pgdat->node_start_pfn: 12812288	<----
[    0.000000] On node 3 totalpages: 4194304
[    0.000000]   Normal zone: 65536 pages used for memmap
[    0.000000]   Normal zone: 4128768 pages, LIFO batch:31
[    0.000000] ACPI: PM-Timer IO Port: 0x2008
[    0.000000] ACPI: Local APIC address 0xfee00000

Thanks.

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
Einsteinring 24, 85609 Dornach
GM: Alberto Bozzo
Reg: Dornach, Landkreis Muenchen
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