linux-kernel - Re: [this_cpu_xx V7 1/8] this_cpu

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Message-ID: <4B270841.2000203@kernel.org>
Date:	Tue, 15 Dec 2009 12:53:37 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Christoph Lameter <cl@...ux-foundation.org>
CC:	linux-kernel@...r.kernel.org, Mel Gorman <mel@....ul.ie>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Subject: Re: [this_cpu_xx V7 1/8] this_cpu_ops: page allocator conversion

Hello,

On 12/15/2009 07:03 AM, Christoph Lameter wrote:
>  static __meminit void zone_pcp_init(struct zone *zone)
>  {
> -	int cpu;
> -	unsigned long batch = zone_batchsize(zone);
> +	/* Use boot pagesets until we have the per cpu allocator up */
> +	zone->pageset = &per_cpu_var(boot_pageset);

Ummm... this scares me a little bit.  Before it was a pointer to
statically allocated area which can be used from basically anywhere.
Now, it's being initialized to a percpu pointer which won't be
available before setup_per_cpu_areas() is complete and the above
initialization takes place from setup_arch() which is before percpu
initialization.  I don't think there's anything which would access
page allocator between the two places, but it still seems a bit risky.
Maybe it's better to keep the boot_pageset a static array?  Or am I
misunderstanding something?

Thanks.

-- 
tejun
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