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powerpc: smp: remove hack to obtain offset of task_struct::cpu

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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>
This commit is contained in:
Ard Biesheuvel 2021-09-14 14:10:34 +02:00
parent bcf9033e54
commit 336868afba
3 changed files with 1 additions and 29 deletions
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11
arch/powerpc/Makefile
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@ -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.

17
arch/powerpc/include/asm/smp.h
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@ -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)

2
arch/powerpc/kernel/asm-offsets.c
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@ -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>