Re: [PATCH v2 06/10] x86/percpu: Clean up percpu_add_return_op()

[Nick Desaulniers <ndesaulniers@google.com>]

On Sat, May 30, 2020 at 3:11 PM Brian Gerst <brgerst@gmail.com> wrote:
>
> The core percpu macros already have a switch on the data size, so the switch
> in the x86 code is redundant and produces more dead code.
>
> Also use appropriate types for the width of the instructions.  This avoids
> errors when compiling with Clang.
>
> Signed-off-by: Brian Gerst <brgerst@gmail.com>

I think it would have been ok to carry forward my reviewed by tag here
from v1, hidden at the bottom of
https://lore.kernel.org/lkml/CAKwvOdn7yC1GVA+6gtNewBSq2BK09y9iNWhv1dPFF5i4kT1+6A@mail.gmail.com/
even though you split removing 'e' into it's own patch.

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>  arch/x86/include/asm/percpu.h | 51 +++++++++++------------------------
>  1 file changed, 16 insertions(+), 35 deletions(-)
>
> diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
> index 9bb5440d98d3..0776a11e7e11 100644
> --- a/arch/x86/include/asm/percpu.h
> +++ b/arch/x86/include/asm/percpu.h
> @@ -199,34 +199,15 @@ do {                                                                      \
>  /*
>   * Add return operation
>   */
> -#define percpu_add_return_op(qual, var, val)                           \
> +#define percpu_add_return_op(size, qual, _var, _val)                   \
>  ({                                                                     \
> -       typeof(var) paro_ret__ = val;                                   \
> -       switch (sizeof(var)) {                                          \
> -       case 1:                                                         \
> -               asm qual ("xaddb %0, "__percpu_arg(1)                   \
> -                           : "+q" (paro_ret__), "+m" (var)             \
> -                           : : "memory");                              \
> -               break;                                                  \
> -       case 2:                                                         \
> -               asm qual ("xaddw %0, "__percpu_arg(1)                   \
> -                           : "+r" (paro_ret__), "+m" (var)             \
> -                           : : "memory");                              \
> -               break;                                                  \
> -       case 4:                                                         \
> -               asm qual ("xaddl %0, "__percpu_arg(1)                   \
> -                           : "+r" (paro_ret__), "+m" (var)             \
> -                           : : "memory");                              \
> -               break;                                                  \
> -       case 8:                                                         \
> -               asm qual ("xaddq %0, "__percpu_arg(1)                   \
> -                           : "+r" (paro_ret__), "+m" (var)             \
> -                           : : "memory");                              \
> -               break;                                                  \
> -       default: __bad_percpu_size();                                   \
> -       }                                                               \
> -       paro_ret__ += val;                                              \
> -       paro_ret__;                                                     \
> +       __pcpu_type_##size paro_tmp__ = __pcpu_cast_##size(_val);       \
> +       asm qual (__pcpu_op2_##size("xadd", "%[tmp]",                   \
> +                                    __percpu_arg([var]))               \
> +                 : [tmp] __pcpu_reg_##size("+", paro_tmp__),           \
> +                   [var] "+m" (_var)                                   \
> +                 : : "memory");                                        \
> +       (typeof(_var))(unsigned long) (paro_tmp__ + _val);              \
>  })
>
>  /*
> @@ -377,16 +358,16 @@ do {                                                                      \
>  #define this_cpu_xchg_2(pcp, nval)     percpu_xchg_op(volatile, pcp, nval)
>  #define this_cpu_xchg_4(pcp, nval)     percpu_xchg_op(volatile, pcp, nval)
>
> -#define raw_cpu_add_return_1(pcp, val)         percpu_add_return_op(, pcp, val)
> -#define raw_cpu_add_return_2(pcp, val)         percpu_add_return_op(, pcp, val)
> -#define raw_cpu_add_return_4(pcp, val)         percpu_add_return_op(, pcp, val)
> +#define raw_cpu_add_return_1(pcp, val)         percpu_add_return_op(1, , pcp, val)
> +#define raw_cpu_add_return_2(pcp, val)         percpu_add_return_op(2, , pcp, val)
> +#define raw_cpu_add_return_4(pcp, val)         percpu_add_return_op(4, , pcp, val)
>  #define raw_cpu_cmpxchg_1(pcp, oval, nval)     percpu_cmpxchg_op(, pcp, oval, nval)
>  #define raw_cpu_cmpxchg_2(pcp, oval, nval)     percpu_cmpxchg_op(, pcp, oval, nval)
>  #define raw_cpu_cmpxchg_4(pcp, oval, nval)     percpu_cmpxchg_op(, pcp, oval, nval)
>
> -#define this_cpu_add_return_1(pcp, val)                percpu_add_return_op(volatile, pcp, val)
> -#define this_cpu_add_return_2(pcp, val)                percpu_add_return_op(volatile, pcp, val)
> -#define this_cpu_add_return_4(pcp, val)                percpu_add_return_op(volatile, pcp, val)
> +#define this_cpu_add_return_1(pcp, val)                percpu_add_return_op(1, volatile, pcp, val)
> +#define this_cpu_add_return_2(pcp, val)                percpu_add_return_op(2, volatile, pcp, val)
> +#define this_cpu_add_return_4(pcp, val)                percpu_add_return_op(4, volatile, pcp, val)
>  #define this_cpu_cmpxchg_1(pcp, oval, nval)    percpu_cmpxchg_op(volatile, pcp, oval, nval)
>  #define this_cpu_cmpxchg_2(pcp, oval, nval)    percpu_cmpxchg_op(volatile, pcp, oval, nval)
>  #define this_cpu_cmpxchg_4(pcp, oval, nval)    percpu_cmpxchg_op(volatile, pcp, oval, nval)
> @@ -418,7 +399,7 @@ do {                                                                        \
>  #define raw_cpu_add_8(pcp, val)                        percpu_add_op(8, , (pcp), val)
>  #define raw_cpu_and_8(pcp, val)                        percpu_to_op(8, , "and", (pcp), val)
>  #define raw_cpu_or_8(pcp, val)                 percpu_to_op(8, , "or", (pcp), val)
> -#define raw_cpu_add_return_8(pcp, val)         percpu_add_return_op(, pcp, val)
> +#define raw_cpu_add_return_8(pcp, val)         percpu_add_return_op(8, , pcp, val)
>  #define raw_cpu_xchg_8(pcp, nval)              raw_percpu_xchg_op(pcp, nval)
>  #define raw_cpu_cmpxchg_8(pcp, oval, nval)     percpu_cmpxchg_op(, pcp, oval, nval)
>
> @@ -427,7 +408,7 @@ do {                                                                        \
>  #define this_cpu_add_8(pcp, val)               percpu_add_op(8, volatile, (pcp), val)
>  #define this_cpu_and_8(pcp, val)               percpu_to_op(8, volatile, "and", (pcp), val)
>  #define this_cpu_or_8(pcp, val)                        percpu_to_op(8, volatile, "or", (pcp), val)
> -#define this_cpu_add_return_8(pcp, val)                percpu_add_return_op(volatile, pcp, val)
> +#define this_cpu_add_return_8(pcp, val)                percpu_add_return_op(8, volatile, pcp, val)
>  #define this_cpu_xchg_8(pcp, nval)             percpu_xchg_op(volatile, pcp, nval)
>  #define this_cpu_cmpxchg_8(pcp, oval, nval)    percpu_cmpxchg_op(volatile, pcp, oval, nval)
>
> --
> 2.25.4
>


-- 
Thanks,
~Nick Desaulniers