highmem: Use this_cpu_xx_return() operations (cfb82434) · Commits · 戴 / test

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>

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

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