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s390/percpu: implement this_cpu_xchg() 

The generic variant has a local_irq_save/restore pair which is quite
expensive. It is sufficient to disable preemption, which is a no-op
with !CONFIG_PREEMPT and then use the regular xchg macro.

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 2012-09-17 06:38:22 +02:00 committed by Martin Schwidefsky
parent 0ed23b3e49
commit 28634a07d3
1 changed files with 18 additions and 0 deletions
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18
arch/s390/include/asm/percpu.h
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@ -84,6 +84,24 @@ do { \
#define this_cpu_cmpxchg_4(pcp, oval, nval) arch_this_cpu_cmpxchg(pcp, oval, nval)
#define this_cpu_cmpxchg_8(pcp, oval, nval) arch_this_cpu_cmpxchg(pcp, oval, nval)
#define arch_this_cpu_xchg(pcp, nval) \
({ \
typeof(pcp) *ptr__; \
typeof(pcp) ret__; \
preempt_disable(); \
ptr__ = __this_cpu_ptr(&(pcp)); \
ret__ = xchg(ptr__, nval); \
preempt_enable(); \
ret__; \
})
#define this_cpu_xchg_1(pcp, nval) arch_this_cpu_xchg(pcp, nval)
#define this_cpu_xchg_2(pcp, nval) arch_this_cpu_xchg(pcp, nval)
#define this_cpu_xchg_4(pcp, nval) arch_this_cpu_xchg(pcp, nval)
#ifdef CONFIG_64BIT
#define this_cpu_xchg_8(pcp, nval) arch_this_cpu_xchg(pcp, nval)
#endif
#include <asm-generic/percpu.h>
#endif /* __ARCH_S390_PERCPU__ */