linux-kernel - Re: Broken "cpualloc: the allocator" patch

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Date:	Wed, 5 Nov 2008 10:57:11 +0200 (EET)
From:	Pekka J Enberg <penberg@...helsinki.fi>
To:	Alexey Dobriyan <adobriyan@...il.com>
cc:	Christoph Lameter <cl@...ux-foundation.org>, rusty@...tcorp.com.au,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	hannes@...urebad.de
Subject: Re: Broken "cpualloc: the allocator" patch

Hi Alexey,

On Tue, Nov 04, 2008 at 09:38:40AM -0600, Christoph Lameter wrote:
> > Works fine here.
> >
> > Do we have the right tree? I repulled my tree on top of Linuses and 
> > things work just fine. Tree is at
> >
> > kernel.org/pub/scm/linux/kernel/git/christoph/work.git cpu_alloc

On Wed, 5 Nov 2008, Alexey Dobriyan wrote:
> Same thing. For reference f622b9e43c8ba1902d4423bef9ae9d89b0254b45 aka
> "cpualloc: the allocator".
> 
> It's BUG_ON(!size) at mm/bootmem.c:438. At cpu_alloc_init():
> 
> __per_cpu_start = ff...80555000
> __per_cpu_end   = ff...8055d3e0
> UNIT_SIZE = 4
> base_percpu_in_units = 8440
> PERCPU_AREA_SIZE = 33760
> nr_units = 0 (bang!)
> 
> MODULES are off.

Yup, makes sense. PERCPU_MODULE_RESERVE is set to zero if !CONFIG_MODULES. 
Is there a reason we don't do something like this in bootmem allocator? 
Hannes?
		Pekka

diff --git a/mm/bootmem.c b/mm/bootmem.c
index ac5a891..ee6431f 100644
--- a/mm/bootmem.c
+++ b/mm/bootmem.c
@@ -435,7 +435,9 @@ static void * __init alloc_bootmem_core(struct bootmem_data *bdata,
 	unsigned long fallback = 0;
 	unsigned long min, max, start, sidx, midx, step;
 
-	BUG_ON(!size);
+	if (!size)
+		return NULL;
+
 	BUG_ON(align & (align - 1));
 	BUG_ON(limit && goal + size > limit);
 
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