linux-kernel - Re: [PATCH 1/1] x86: Add check for node passed to node_to

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Date:	Sun, 29 Jun 2008 05:40:09 -0700
From:	Mike Travis <travis@....com>
To:	Vegard Nossum <vegard.nossum@...il.com>
CC:	Ingo Molnar <mingo@...e.hu>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	mm-commits@...r.kernel.org, Yinghai Lu <yhlu.kernel@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] x86: Add check for node passed to node_to_cpumask
 V3

Vegard Nossum wrote:
> On Fri, Jun 27, 2008 at 8:03 PM, Mike Travis <travis@....com> wrote:
>>> So if CONFIG_DEBUG_RODATA=y, I believe we'll see first this warning,
>>> then a panic (after all). Would it be better to make cpu_mask_none
>>> non-const, in spirit of trying to continue as far as possible? I don't
>>> really know if it matters, though. It seems that fedora kernels at
>>> least ship with a default of DEBUG_RODATA=y.
>>>
> 
> ...
> 
>> Ingo asked me to add the "const".  But it would be a mistake to use
>> node_to_cpumask_ptr to modify the map... numa_set/clear_node is the
>> proper way to modify the maps.  Hmm, maybe I should add "const" to
>> the real node_to_cpumask_ptr function, at least then the compiler
>> would help spot illegal usages.
> 
> That sounds like a brilliant idea, as long as none of the callers
> expect it to be non-const.

Being that I modified all the callers to use this new function, I did
verify that each caller expected it to be read only... ;-)
> 
> I changed it to return const to see, and built allmodconfig + a few
> randconfigs without error (well, warning). There are not that many
> users of this function anyway.

Did any violate the read-only nature of the call?
> 
> BTW, what's up with the topology.h/setup_percpu.c mismatch, when
> topology.c exists as well?

Topology.h supplies the generic usage which is to define a local cpumask
variable, fill it, and then return a pointer to it.  This is for arch's
that do not maintain a separate node_to_cpumask_map[] but allows a
compatible call interface.
> 
> 
> Vegard
> 

Thanks!
Mike

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