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s390/bitops: implement cache friendly test_and_set_bit_lock

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The generic implementation for test_and_set_bit_lock in include/asm-generic
uses the standard test_and_set_bit operation. This is done with either a
'csg' or a 'loag' instruction. For both version the cache line is fetched
exclusively, even if the bit is already set. The result is an increase in
cache traffic, for a contented lock this is a bad idea.

Acked-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2015-08-20 12:57:33 +02:00
parent 5614dd920a
commit acdc9fc9a8
1 changed files with 22 additions and 1 deletions
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23
arch/s390/include/asm/bitops.h
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@ -276,6 +276,28 @@ static inline int test_bit(unsigned long nr, const volatile unsigned long *ptr)
return (*addr >> (nr & 7)) & 1;
}
static inline int test_and_set_bit_lock(unsigned long nr,
volatile unsigned long *ptr)
{
if (test_bit(nr, ptr))
return 1;
return test_and_set_bit(nr, ptr);
}
static inline void clear_bit_unlock(unsigned long nr,
volatile unsigned long *ptr)
{
smp_mb__before_atomic();
clear_bit(nr, ptr);
}
static inline void __clear_bit_unlock(unsigned long nr,
volatile unsigned long *ptr)
{
smp_mb();
__clear_bit(nr, ptr);
}
/*
* Functions which use MSB0 bit numbering.
* On an s390x system the bits are numbered:
@ -446,7 +468,6 @@ static inline int fls(int word)
#include <asm-generic/bitops/ffz.h>
#include <asm-generic/bitops/find.h>
#include <asm-generic/bitops/hweight.h>
#include <asm-generic/bitops/lock.h>
#include <asm-generic/bitops/sched.h>
#include <asm-generic/bitops/le.h>
#include <asm-generic/bitops/ext2-atomic-setbit.h>