9d84fb27fa
Commit c02433dd6de32f04 ("arm64: split thread_info from task stack")
inverted the relationship between get_current() and
current_thread_info(), with sp_el0 now holding the current task_struct
rather than the current thead_info. The new implementation of
get_current() prevents the compiler from being able to optimize repeated
calls to either, resulting in a noticeable penalty in some
microbenchmarks.
This patch restores the previous optimisation by implementing
get_current() in the same way as our old current_thread_info(), using a
non-volatile asm statement.
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Reported-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
31 lines
503 B
C
31 lines
503 B
C
#ifndef __ASM_CURRENT_H
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#define __ASM_CURRENT_H
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#include <linux/compiler.h>
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#include <asm/sysreg.h>
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#ifndef __ASSEMBLY__
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struct task_struct;
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/*
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* We don't use read_sysreg() as we want the compiler to cache the value where
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* possible.
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*/
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static __always_inline struct task_struct *get_current(void)
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{
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unsigned long sp_el0;
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asm ("mrs %0, sp_el0" : "=r" (sp_el0));
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return (struct task_struct *)sp_el0;
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}
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#define current get_current()
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#endif /* __ASSEMBLY__ */
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#endif /* __ASM_CURRENT_H */
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