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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: Peter 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: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2019-02-27 11:09:56 +01:00 committed by Ingo Molnar
parent 8dc2d993cf
commit 2234a6d3a2
1 changed files with 16 additions and 4 deletions
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20
arch/x86/include/asm/percpu.h
View File

@ -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)