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Commita76d7bd96d("ARM: 7467/1: mutex: use generic xchg-based implementation for ARMv6+") removed the barrier-less, ARM-specific mutex implementation in favour of the generic xchg-based code. Since then, a bug was uncovered in the xchg code when running on SMP platforms, due to interactions between the locking paths and the MUTEX_SPIN_ON_OWNER code. This was fixed in0bce9c46bf("mutex: place lock in contended state after fastpath_lock failure"), however, the atomic_dec-based mutex algorithm is now marginally more efficient for ARM (~0.5% improvement in hackbench scores on dual A15). This patch moves ARMv6+ platforms to the atomic_dec-based mutex code. Acked-by: Nicolas Pitre <nico@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
22 lines
577 B
C
22 lines
577 B
C
/*
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* arch/arm/include/asm/mutex.h
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*
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* ARM optimized mutex locking primitives
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*
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* Please look into asm-generic/mutex-xchg.h for a formal definition.
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*/
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#ifndef _ASM_MUTEX_H
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#define _ASM_MUTEX_H
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/*
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* On pre-ARMv6 hardware this results in a swp-based implementation,
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* which is the most efficient. For ARMv6+, we have exclusive memory
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* accessors and use atomic_dec to avoid the extra xchg operations
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* on the locking slowpaths.
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*/
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#if __LINUX_ARM_ARCH__ < 6
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#include <asm-generic/mutex-xchg.h>
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#else
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#include <asm-generic/mutex-dec.h>
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#endif
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#endif /* _ASM_MUTEX_H */
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