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Commit 2234a6d3 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
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x86/percpu: Optimize raw_cpu_xchg() 



Since raw_cpu_xchg() doesn't need to be IRQ-safe, like
this_cpu_xchg(), we can use a simple load-store instead of the cmpxchg
loop.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 8dc2d993

arch/x86/include/asm/percpu.h

+16 −4
Original line number Diff line number Diff line
@@ -407,9 +407,21 @@ do { \ 
#define raw_cpu_or_1(pcp, val)		percpu_to_op(, "or", (pcp), val)

#define raw_cpu_or_2(pcp, val)		percpu_to_op(, "or", (pcp), val)

#define raw_cpu_or_4(pcp, val)		percpu_to_op(, "or", (pcp), val)

#define raw_cpu_xchg_1(pcp, val)	percpu_xchg_op(, pcp, val)

#define raw_cpu_xchg_2(pcp, val)	percpu_xchg_op(, pcp, val)

#define raw_cpu_xchg_4(pcp, val)	percpu_xchg_op(, pcp, val)



/*

 * raw_cpu_xchg() can use a load-store since it is not required to be

 * IRQ-safe.

 */

#define raw_percpu_xchg_op(var, nval)					\

({									\

	typeof(var) pxo_ret__ = raw_cpu_read(var);			\

	raw_cpu_write(var, (nval));					\

	pxo_ret__;							\

})



#define raw_cpu_xchg_1(pcp, val)	raw_percpu_xchg_op(pcp, val)

#define raw_cpu_xchg_2(pcp, val)	raw_percpu_xchg_op(pcp, val)

#define raw_cpu_xchg_4(pcp, val)	raw_percpu_xchg_op(pcp, val)



#define this_cpu_read_1(pcp)		percpu_from_op(volatile, "mov", pcp)

#define this_cpu_read_2(pcp)		percpu_from_op(volatile, "mov", pcp)
@@ -472,7 +484,7 @@ do { \ 
#define raw_cpu_and_8(pcp, val)			percpu_to_op(, "and", (pcp), val)

#define raw_cpu_or_8(pcp, val)			percpu_to_op(, "or", (pcp), val)

#define raw_cpu_add_return_8(pcp, val)		percpu_add_return_op(, pcp, val)

#define raw_cpu_xchg_8(pcp, nval)		percpu_xchg_op(, pcp, nval)

#define raw_cpu_xchg_8(pcp, nval)		raw_percpu_xchg_op(pcp, nval)

#define raw_cpu_cmpxchg_8(pcp, oval, nval)	percpu_cmpxchg_op(, pcp, oval, nval)



#define this_cpu_read_8(pcp)			percpu_from_op(volatile, "mov", pcp)