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From: Tejun Heo <tj@kernel.org>
To: Namhyung Kim <namhyung@gmail.com>
Cc: linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] percpu: remove address_space attribute if !SMP
Date: Fri, 06 Aug 2010 12:57:10 +0000	[thread overview]
Message-ID: <4C5C06A6.7070206@kernel.org> (raw)
In-Reply-To: <1281099197.1655.11.camel@leonhard>

Hello,

On 08/06/2010 02:53 PM, Namhyung Kim wrote:
>> But they should still be accessed through the accessors and if they
>> are accessed through accessors, there shouldn't be sparse warnings
>> regarding them.  Maybe UP accessors are missing proper markups?  Do
>> those warnings only happen on UP config?
>>
> 
> They do nothing on UP.
> quoting from include/asm-generic.h:
> 
> #else /* ! SMP */
> 
> #define per_cpu(var, cpu)			(*((void)(cpu), &(var)))
> #define __get_cpu_var(var)			(var)
> #define __raw_get_cpu_var(var)			(var)
> #define this_cpu_ptr(ptr) per_cpu_ptr(ptr, 0)
> #define __this_cpu_ptr(ptr) this_cpu_ptr(ptr)
> 
> #endif	/* SMP */

Ah, I see.  Then, the right thing to do is to add proper checking and
markups to UP accessors matching the SMP ones.
ie. __verify_pcpu_ptr() verification followed by __kernel __force
casting.  Are you interested in doing it?

Thanks.

-- 
tejun

WARNING: multiple messages have this Message-ID (diff)
From: Tejun Heo <tj@kernel.org>
To: Namhyung Kim <namhyung@gmail.com>
Cc: linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] percpu: remove address_space attribute if !SMP
Date: Fri, 06 Aug 2010 14:57:10 +0200	[thread overview]
Message-ID: <4C5C06A6.7070206@kernel.org> (raw)
In-Reply-To: <1281099197.1655.11.camel@leonhard>

Hello,

On 08/06/2010 02:53 PM, Namhyung Kim wrote:
>> But they should still be accessed through the accessors and if they
>> are accessed through accessors, there shouldn't be sparse warnings
>> regarding them.  Maybe UP accessors are missing proper markups?  Do
>> those warnings only happen on UP config?
>>
> 
> They do nothing on UP.
> quoting from include/asm-generic.h:
> 
> #else /* ! SMP */
> 
> #define per_cpu(var, cpu)			(*((void)(cpu), &(var)))
> #define __get_cpu_var(var)			(var)
> #define __raw_get_cpu_var(var)			(var)
> #define this_cpu_ptr(ptr) per_cpu_ptr(ptr, 0)
> #define __this_cpu_ptr(ptr) this_cpu_ptr(ptr)
> 
> #endif	/* SMP */

Ah, I see.  Then, the right thing to do is to add proper checking and
markups to UP accessors matching the SMP ones.
ie. __verify_pcpu_ptr() verification followed by __kernel __force
casting.  Are you interested in doing it?

Thanks.

-- 
tejun

  reply	other threads:[~2010-08-06 12:57 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-08-06 12:46 [PATCH] percpu: remove address_space attribute if !SMP Namhyung Kim
2010-08-06 12:46 ` Namhyung Kim
2010-08-06 12:49 ` Tejun Heo
2010-08-06 12:49   ` Tejun Heo
2010-08-06 12:53   ` Namhyung Kim
2010-08-06 12:53     ` Namhyung Kim
2010-08-06 12:57     ` Tejun Heo [this message]
2010-08-06 12:57       ` Tejun Heo
2010-08-06 13:23       ` Namhyung Kim
2010-08-06 13:23         ` Namhyung Kim
2010-08-06 13:37         ` Tejun Heo
2010-08-06 13:37           ` Tejun Heo
2010-08-06 13:46           ` Namhyung Kim
2010-08-06 13:46             ` Namhyung Kim

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