linux-kernel - Re: [PATCH] percpu,lockdep: implement and use is_static_percpu

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Message-ID: <4B963441.40000@kernel.org>
Date:	Tue, 09 Mar 2010 20:42:57 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Valdis.Kletnieks@...edu, Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] percpu,lockdep: implement and use is_static_percpu_address()

Hello, Peter.

On 03/09/2010 08:25 PM, Peter Zijlstra wrote:
>> +/* can't distinguish from other static vars, always false */
>> +static inline bool is_static_percpu_address(unsigned long addr)
>> +{
>> +	return false;
>> +}
> 
> At this point it might make sense to simply fail to compile if lockdep
> is enabled as well.
> 
> I'm not sure if there's many SMP archs that don't have this and do have
> lockdep, but simply failing this test isn't really an option.

That might be better.  Returning %false isn't that bad tho.  There
really is no distinction between percpu and !percpu variable on UP and
static variable address match will catch both.

>>  /**
>> + * is_static_percpu_address - test whether address is from static percpu area
>> + * @addr: address to test
>> + *
>> + * Test whether @addr belongs to static percpu area.  Module static
>> + * percpu areas allocated via __alloc_reserved_percpu() is not
>> + * considered.  Use is_module_address() for those.
>> + *
>> + * RETURNS:
>> + * %true if @addr is from static percpu area, %false otherwise.
>> + */
> 
> So is_module_address() will only return true for static per-cpu module
> storage, right?

Right, got confused there.  I'll update is_static_percpu_address() to
test for reserved regions too.

Thanks for the review.

-- 
tejun
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