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Commit acdc9fc9 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

s390/bitops: implement cache friendly test_and_set_bit_lock 



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: default avatarHendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 5614dd92

arch/s390/include/asm/bitops.h

+22 −1
Original line number Diff line number Diff line
@@ -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>