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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: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Christoph Lameter 2010-12-06 11:40:03 -06:00 committed by Tejun Heo
parent 908ee0f122
commit cfb8243495
1 changed files with 8 additions and 5 deletions
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13
include/linux/highmem.h
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@ -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