From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH 7/8] percpu: add __percpu sparse annotations to	hw_breakpoint
Date: Tue, 26 Jan 2010 11:13:59 +0900
Message-ID: <4B5E4FE7.30700@kernel.org>
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Cc: linux-kernel@vger.kernel.org, axboe@kernel.dk,
	rusty@rustcorp.com.au, akpm@linux-foundation.org,
	ebiederm@xmission.com, tytso@mit.edu, Trond.Myklebust@netapp.com,
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To: Frederic Weisbecker <fweisbec@gmail.com>
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Sender: linux-kernel-owner@vger.kernel.org
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Hello,

On 01/26/2010 11:01 AM, Frederic Weisbecker wrote:
> So, may be it considers you are applying the address space overriding
> to the pointer to the type and not to the type itself.
> 
> Consider:
> 
> 	int __percpu i;
> 
> What you do above *might* be considered as if SHIFT_PERCPU_PTR
> returns something of a type:
> 
> 	int * __percpu i;
> 
> So the pointer is in the normal address space, but its content is in
> __percpu address space.
> 
> What if you do this:
> 
> 
> #define SHIFT_PERCPU_PTR(__p, __offset)      ({                      \
>       __verify_pcpu_ptr((__p));                                       \
>       RELOC_HIDE((__p), (__offset)); \
> })
> 
> #define per_cpu(var, cpu) \
>       (typeof(var) __kernel __force)(*SHIFT_PERCPU_PTR(&(var), per_cpu_offset(cpu)))

arch/x86/kernel/cpu/common.c:1149:20: warning: cast to non-scalar
arch/x86/kernel/cpu/common.c:1149:20: error: strange non-value function or array
  CC      arch/x86/kernel/cpu/common.o
arch/x86/kernel/cpu/common.c: In function 'cpu_init':
arch/x86/kernel/cpu/common.c:1149: error: cast specifies array type

Can't cast that way.  :-(

-- 
tejun