linux-kernel - Re: [patch 3/4] cpu alloc: The allocator

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Message-ID: <48D3A4F5.9010804@linux-foundation.org>
Date:	Fri, 19 Sep 2008 08:11:17 -0500
From:	Christoph Lameter <cl@...ux-foundation.org>
To:	Pekka Enberg <penberg@...helsinki.fi>
CC:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-mm@...r.kernel.org, jeremy@...p.org, ebiederm@...ssion.com,
	travis@....com, herbert@...dor.apana.org.au, xemul@...nvz.org
Subject: Re: [patch 3/4] cpu alloc: The allocator

Pekka Enberg wrote:
> 
>> + *
>> + * (C) 2008 SGI, Christoph Lameter <clameter@....com>
> 
> You probably want to drop that defunct email address.

Ok.


> I found the first sentence a bit misleading. You can be easily fooled
> into thinking "simultaneously" means there's no global locking (well,
> I was).

Reformulated the sentence.


>> +       BUG_ON(index >= nr_units ||
>> +               !test_bit(index, cpu_alloc_map) ||
>> +               !test_bit(index + units - 1, cpu_alloc_map));
> 
> Why not turn this into three separate BUG_ON() calls? It's much easier
> to figure out the offending expression like that. Also, maybe we want
> these to be WARN_ON() calls (and early return) to avoid early boot
> panic?

Ok these are basically for two error conditions:

1. Size to large

2. address out of bounds

So I made them into two bugs.

I thought we could handle early boot panics with early_printk?


>> Index: linux-2.6/arch/x86/kernel/setup_percpu.c
>> ===================================================================
>> --- linux-2.6.orig/arch/x86/kernel/setup_percpu.c       2008-09-16 19:04:30.000000000 -0700
>> +++ linux-2.6/arch/x86/kernel/setup_percpu.c    2008-09-16 19:04:48.000000000 -0700
>> @@ -144,6 +144,7 @@ void __init setup_per_cpu_areas(void)
>>        char *ptr;
>>        int cpu;
>>
>> +       cpu_alloc_init();
>>        /* Setup cpu_pda map */
>>        setup_cpu_pda_map();
> 
> We need to do sparc, powerpc, and ia64 too, right?

Correct.
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