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    SubjectRe: [PATCH] unbreak alpha percpu
    On Fri, Apr 10, 2009 at 04:12:24PM +0100, Al Viro wrote:
    > asm-generic/percpu.h is *NOT* included by every asm/percpu.h out there.
    > Namely, alpha can't use it since it needs the var name in
    > SHIFT_PERCPU_PTR - &per_cpu_var(var) won't do at all. So adding stuff
    > to asm-generic/percpu.h and expecting it to be picked by everything
    > is not going to work.
    >
    > Frankly, I'd rather have SHIFT_PERCPU_PTR() calling conventions changed,
    > but for now the patch below will do.
    >
    > Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

    Alternative patch (changing SHIFT_PERCPU_PTR() arguments and switching
    alpha to asm-generic/percpu.h) would be this (only build-tested, though):

    diff --git a/arch/alpha/include/asm/percpu.h b/arch/alpha/include/asm/percpu.h
    index 3495e8e..1c52a2d 100644
    --- a/arch/alpha/include/asm/percpu.h
    +++ b/arch/alpha/include/asm/percpu.h
    @@ -3,33 +3,8 @@
    #include <linux/compiler.h>
    #include <linux/threads.h>

    -/*
    - * Determine the real variable name from the name visible in the
    - * kernel sources.
    - */
    -#define per_cpu_var(var) per_cpu__##var
    -
    #ifdef CONFIG_SMP
    -
    -/*
    - * per_cpu_offset() is the offset that has to be added to a
    - * percpu variable to get to the instance for a certain processor.
    - */
    -extern unsigned long __per_cpu_offset[NR_CPUS];
    -
    -#define per_cpu_offset(x) (__per_cpu_offset[x])
    -
    -#define __my_cpu_offset per_cpu_offset(raw_smp_processor_id())
    -#ifdef CONFIG_DEBUG_PREEMPT
    -#define my_cpu_offset per_cpu_offset(smp_processor_id())
    -#else
    -#define my_cpu_offset __my_cpu_offset
    -#endif
    -
    -#ifndef MODULE
    -#define SHIFT_PERCPU_PTR(var, offset) RELOC_HIDE(&per_cpu_var(var), (offset))
    -#define PER_CPU_ATTRIBUTES
    -#else
    +#ifdef MODULE
    /*
    * To calculate addresses of locally defined variables, GCC uses 32-bit
    * displacement from the GP. Which doesn't work for per cpu variables in
    @@ -39,40 +14,15 @@ extern unsigned long __per_cpu_offset[NR_CPUS];
    * ldq instruction with a 'literal' relocation.
    */
    #define SHIFT_PERCPU_PTR(var, offset) ({ \
    - extern int simple_identifier_##var(void); \
    unsigned long __ptr, tmp_gp; \
    asm ( "br %1, 1f \n\
    1: ldgp %1, 0(%1) \n\
    ldq %0, per_cpu__" #var"(%1)\t!literal" \
    : "=&r"(__ptr), "=&r"(tmp_gp)); \
    (typeof(&per_cpu_var(var)))(__ptr + (offset)); })
    -
    -#define PER_CPU_ATTRIBUTES __used
    -
    #endif /* MODULE */
    -
    -/*
    - * A percpu variable may point to a discarded regions. The following are
    - * established ways to produce a usable pointer from the percpu variable
    - * offset.
    - */
    -#define per_cpu(var, cpu) \
    - (*SHIFT_PERCPU_PTR(var, per_cpu_offset(cpu)))
    -#define __get_cpu_var(var) \
    - (*SHIFT_PERCPU_PTR(var, my_cpu_offset))
    -#define __raw_get_cpu_var(var) \
    - (*SHIFT_PERCPU_PTR(var, __my_cpu_offset))
    -
    -#else /* ! SMP */
    -
    -#define per_cpu(var, cpu) (*((void)(cpu), &per_cpu_var(var)))
    -#define __get_cpu_var(var) per_cpu_var(var)
    -#define __raw_get_cpu_var(var) per_cpu_var(var)
    -
    -#define PER_CPU_ATTRIBUTES
    -
    #endif /* SMP */

    -#define DECLARE_PER_CPU(type, name) extern __typeof__(type) per_cpu_var(name)
    +#include <asm-generic/percpu.h>

    #endif /* __ALPHA_PERCPU_H */
    diff --git a/arch/s390/include/asm/percpu.h b/arch/s390/include/asm/percpu.h
    index 408d60b..6a71d73 100644
    --- a/arch/s390/include/asm/percpu.h
    +++ b/arch/s390/include/asm/percpu.h
    @@ -13,20 +13,18 @@
    */
    #if defined(__s390x__) && defined(MODULE)

    -#define SHIFT_PERCPU_PTR(ptr,offset) (({ \
    - extern int simple_identifier_##var(void); \
    +#define SHIFT_PERCPU_PTR(var,offset) (({ \
    unsigned long *__ptr; \
    asm ( "larl %0, %1@GOTENT" \
    - : "=a" (__ptr) : "X" (ptr) ); \
    - (typeof(ptr))((*__ptr) + (offset)); }))
    + : "=a" (__ptr) : "X" (&per_cpu_var(var)) ); \
    + (typeof(&per_cpu_var(var)))((*__ptr) + (offset)); }))

    #else

    -#define SHIFT_PERCPU_PTR(ptr, offset) (({ \
    - extern int simple_identifier_##var(void); \
    +#define SHIFT_PERCPU_PTR(var, offset) (({ \
    unsigned long __ptr; \
    - asm ( "" : "=a" (__ptr) : "0" (ptr) ); \
    - (typeof(ptr)) (__ptr + (offset)); }))
    + asm ( "" : "=a" (__ptr) : "0" (&per_cpu_var(var)) ); \
    + (typeof(&per_cpu_var(var))) (__ptr + (offset)); }))

    #endif

    diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
    index 00f45ff..7463700 100644
    --- a/include/asm-generic/percpu.h
    +++ b/include/asm-generic/percpu.h
    @@ -42,10 +42,10 @@ extern unsigned long __per_cpu_offset[NR_CPUS];
    /*
    * Add a offset to a pointer but keep the pointer as is.
    *
    - * Only S390 provides its own means of moving the pointer.
    + * Only S390 and Alpha provide their own means of moving the pointer.
    */
    #ifndef SHIFT_PERCPU_PTR
    -#define SHIFT_PERCPU_PTR(__p, __offset) RELOC_HIDE((__p), (__offset))
    +#define SHIFT_PERCPU_PTR(__v, __offset) RELOC_HIDE(&per_cpu_var(__v), (__offset))
    #endif

    /*
    @@ -54,11 +54,11 @@ extern unsigned long __per_cpu_offset[NR_CPUS];
    * offset.
    */
    #define per_cpu(var, cpu) \
    - (*SHIFT_PERCPU_PTR(&per_cpu_var(var), per_cpu_offset(cpu)))
    + (*SHIFT_PERCPU_PTR(var, per_cpu_offset(cpu)))
    #define __get_cpu_var(var) \
    - (*SHIFT_PERCPU_PTR(&per_cpu_var(var), my_cpu_offset))
    + (*SHIFT_PERCPU_PTR(var, my_cpu_offset))
    #define __raw_get_cpu_var(var) \
    - (*SHIFT_PERCPU_PTR(&per_cpu_var(var), __my_cpu_offset))
    + (*SHIFT_PERCPU_PTR(var, __my_cpu_offset))


    #ifdef CONFIG_HAVE_SETUP_PER_CPU_AREA

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      Last update: 2009-04-10 17:49    [W:0.030 / U:0.264 seconds]
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