Subject: Re: [PATCH 7/8] percpu: add __percpu sparse annotations to hw_breakpoint

From: Al Viro <[email-masked]>
Date: Tue, 26 Jan 2010 02:32:38 +0000

On Tue, Jan 26, 2010 at 11:16:42AM +0900, Tejun Heo wrote:

> # define RELOC_HIDE(ptr, off)					\
>   ({ unsigned long __ptr;					\
>      __ptr = (unsigned long) (ptr);				\
>     (typeof(ptr)) (__ptr + (off)); })
> 
> #define __verify_pcpu_ptr(ptr)	do {					\
> 	const void __percpu *__vpp_verify = (typeof(ptr))NULL;		\
> 	(void)__vpp_verify;						\
> } while (0)
> 
> /* Weird cast keeps both GCC and sparse happy. */
> #define SHIFT_PERCPU_PTR(__p, __offset)	({				\
> 	__verify_pcpu_ptr((__p));					\
> 	RELOC_HIDE((typeof(*(__p)) __kernel __force *)(__p), (__offset)); \
> })
> 
> #define per_cpu(var, cpu) \
> 	(*SHIFT_PERCPU_PTR(&(var), per_cpu_offset(cpu)))

Eh...  You are leaving that noderef in place in case of array.  And _that_
is not an address space, so casts to AS 0 won't do you any good.