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    Subject[PATCH v2 6/7] powerpc: smp: remove hack to obtain offset of task_struct::cpu
    Date
    Instead of relying on awful hacks to obtain the offset of the cpu field
    in struct task_struct, move it back into struct thread_info, which does
    not create the same level of circular dependency hell when trying to
    include the header file that defines it.

    Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
    Acked-by: Mark Rutland <mark.rutland@arm.com>
    Acked-by: Michael Ellerman <mpe@ellerman.id.au>
    ---
    arch/powerpc/Makefile | 11 -----------
    arch/powerpc/include/asm/smp.h | 17 +----------------
    arch/powerpc/kernel/asm-offsets.c | 2 --
    3 files changed, 1 insertion(+), 29 deletions(-)

    diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
    index aa6808e70647..54cad1faa5d0 100644
    --- a/arch/powerpc/Makefile
    +++ b/arch/powerpc/Makefile
    @@ -446,17 +446,6 @@ else
    endif
    endif

    -ifdef CONFIG_SMP
    -ifdef CONFIG_PPC32
    -prepare: task_cpu_prepare
    -
    -PHONY += task_cpu_prepare
    -task_cpu_prepare: prepare0
    - $(eval KBUILD_CFLAGS += -D_TASK_CPU=$(shell awk '{if ($$2 == "TASK_CPU") print $$3;}' include/generated/asm-offsets.h))
    -
    -endif # CONFIG_PPC32
    -endif # CONFIG_SMP
    -
    PHONY += checkbin
    # Check toolchain versions:
    # - gcc-4.6 is the minimum kernel-wide version so nothing required.
    diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
    index 7ef1cd8168a0..007332a4a732 100644
    --- a/arch/powerpc/include/asm/smp.h
    +++ b/arch/powerpc/include/asm/smp.h
    @@ -87,22 +87,7 @@ int is_cpu_dead(unsigned int cpu);
    /* 32-bit */
    extern int smp_hw_index[];

    -/*
    - * This is particularly ugly: it appears we can't actually get the definition
    - * of task_struct here, but we need access to the CPU this task is running on.
    - * Instead of using task_struct we're using _TASK_CPU which is extracted from
    - * asm-offsets.h by kbuild to get the current processor ID.
    - *
    - * This also needs to be safeguarded when building asm-offsets.s because at
    - * that time _TASK_CPU is not defined yet. It could have been guarded by
    - * _TASK_CPU itself, but we want the build to fail if _TASK_CPU is missing
    - * when building something else than asm-offsets.s
    - */
    -#ifdef GENERATING_ASM_OFFSETS
    -#define raw_smp_processor_id() (0)
    -#else
    -#define raw_smp_processor_id() (*(unsigned int *)((void *)current + _TASK_CPU))
    -#endif
    +#define raw_smp_processor_id() (current_thread_info()->cpu)
    #define hard_smp_processor_id() (smp_hw_index[smp_processor_id()])

    static inline int get_hard_smp_processor_id(int cpu)
    diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
    index e37e4546034e..cc05522f50bf 100644
    --- a/arch/powerpc/kernel/asm-offsets.c
    +++ b/arch/powerpc/kernel/asm-offsets.c
    @@ -9,8 +9,6 @@
    * #defines from the assembly-language output.
    */

    -#define GENERATING_ASM_OFFSETS /* asm/smp.h */
    -
    #include <linux/compat.h>
    #include <linux/signal.h>
    #include <linux/sched.h>
    --
    2.30.2
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