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Commit cfb82434 authored by Christoph Lameter's avatar Christoph Lameter Committed by Tejun Heo
Browse files

highmem: Use this_cpu_xx_return() operations 



Use this_cpu operations to optimize access primitives for highmem.

The main effect is the avoidance of address calculations through the
use of a segment prefix.

V3->V4
	- kmap_atomic_idx: Do not return a value.
	- Use __this_cpu_dec without HIGHMEM_DEBUG

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: default avatarH. Peter Anvin <hpa@zytor.com>
Signed-off-by: default avatarChristoph Lameter <cl@linux.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 908ee0f1

include/linux/highmem.h

+8 −5
Original line number Diff line number Diff line
@@ -81,7 +81,8 @@ DECLARE_PER_CPU(int, __kmap_atomic_idx); 


static inline int kmap_atomic_idx_push(void)

{

	int idx = __get_cpu_var(__kmap_atomic_idx)++;

	int idx = __this_cpu_inc_return(__kmap_atomic_idx) - 1;



#ifdef CONFIG_DEBUG_HIGHMEM

	WARN_ON_ONCE(in_irq() && !irqs_disabled());

	BUG_ON(idx > KM_TYPE_NR);
@@ -91,16 +92,18 @@ static inline int kmap_atomic_idx_push(void) 


static inline int kmap_atomic_idx(void)

{

	return __get_cpu_var(__kmap_atomic_idx) - 1;

	return __this_cpu_read(__kmap_atomic_idx) - 1;

}



static inline int kmap_atomic_idx_pop(void)

static inline void kmap_atomic_idx_pop(void)

{

	int idx = --__get_cpu_var(__kmap_atomic_idx);

#ifdef CONFIG_DEBUG_HIGHMEM

	int idx = __this_cpu_dec_return(__kmap_atomic_idx);



	BUG_ON(idx < 0);

#else

	__this_cpu_dec(__kmap_atomic_idx);

#endif

	return idx;

}



#endif