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[S390] percpu: implement arch specific irqsafe_cpu_ops 

Implement arch specific irqsafe_cpu ops. The arch specific ops do not
disable/enable interrupts since that is an expensive operation. Instead
we disable preemption and perform a compare and swap loop.
Since on server distros (the ones we care about) preemption is disabled
the preempt_disable()/preempt_enable() pair is a nop.
In the end this code should be faster than the generic one.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2011-05-23 10:24:32 +02:00 committed by Martin Schwidefsky
parent add7490c27
commit 4c2241fd42
2 changed files with 68 additions and 1 deletions
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1
arch/s390/include/asm/cmpxchg.h
View File

@ -167,7 +167,6 @@ static inline unsigned long __cmpxchg(void *ptr, unsigned long old,
#ifdef CONFIG_64BIT
#define cmpxchg64(ptr, o, n) \
({ \
BUILD_BUG_ON(sizeof(*(ptr)) != 8); \
cmpxchg((ptr), (o), (n)); \
})
#else /* CONFIG_64BIT */

68
arch/s390/include/asm/percpu.h
View File

@ -1,6 +1,9 @@
#ifndef __ARCH_S390_PERCPU__
#define __ARCH_S390_PERCPU__
#include <linux/preempt.h>
#include <asm/cmpxchg.h>
/*
* s390 uses its own implementation for per cpu data, the offset of
* the cpu local data area is cached in the cpu's lowcore memory.
@ -16,6 +19,71 @@
#define ARCH_NEEDS_WEAK_PER_CPU
#endif
#define arch_irqsafe_cpu_to_op(pcp, val, op) \
do { \
typedef typeof(pcp) pcp_op_T__; \
pcp_op_T__ old__, new__, prev__; \
pcp_op_T__ *ptr__; \
preempt_disable(); \
ptr__ = __this_cpu_ptr(&(pcp)); \
prev__ = *ptr__; \
do { \
old__ = prev__; \
new__ = old__ op (val); \
switch (sizeof(*ptr__)) { \
case 8: \
prev__ = cmpxchg64(ptr__, old__, new__); \
break; \
default: \
prev__ = cmpxchg(ptr__, old__, new__); \
} \
} while (prev__ != old__); \
preempt_enable(); \
} while (0)
#define irqsafe_cpu_add_1(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, +)
#define irqsafe_cpu_add_2(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, +)
#define irqsafe_cpu_add_4(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, +)
#define irqsafe_cpu_add_8(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, +)
#define irqsafe_cpu_and_1(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, &)
#define irqsafe_cpu_and_2(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, &)
#define irqsafe_cpu_and_4(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, &)
#define irqsafe_cpu_and_8(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, &)
#define irqsafe_cpu_or_1(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, |)
#define irqsafe_cpu_or_2(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, |)
#define irqsafe_cpu_or_4(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, |)
#define irqsafe_cpu_or_8(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, |)
#define irqsafe_cpu_xor_1(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, ^)
#define irqsafe_cpu_xor_2(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, ^)
#define irqsafe_cpu_xor_4(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, ^)
#define irqsafe_cpu_xor_8(pcp, val) arch_irqsafe_cpu_to_op(pcp, val, ^)
#define arch_irqsafe_cpu_cmpxchg(pcp, oval, nval) \
({ \
typedef typeof(pcp) pcp_op_T__; \
pcp_op_T__ ret__; \
pcp_op_T__ *ptr__; \
preempt_disable(); \
ptr__ = __this_cpu_ptr(&(pcp)); \
switch (sizeof(*ptr__)) { \
case 8: \
ret__ = cmpxchg64(ptr__, oval, nval); \
break; \
default: \
ret__ = cmpxchg(ptr__, oval, nval); \
} \
preempt_enable(); \
ret__; \
})
#define irqsafe_cpu_cmpxchg_1(pcp, oval, nval) arch_irqsafe_cpu_cmpxchg(pcp, oval, nval)
#define irqsafe_cpu_cmpxchg_2(pcp, oval, nval) arch_irqsafe_cpu_cmpxchg(pcp, oval, nval)
#define irqsafe_cpu_cmpxchg_4(pcp, oval, nval) arch_irqsafe_cpu_cmpxchg(pcp, oval, nval)
#define irqsafe_cpu_cmpxchg_8(pcp, oval, nval) arch_irqsafe_cpu_cmpxchg(pcp, oval, nval)
#include <asm-generic/percpu.h>
#endif /* __ARCH_S390_PERCPU__ */