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Commit 4117b021 authored by Akinobu Mita's avatar Akinobu Mita Committed by Linus Torvalds
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[PATCH] bitops: generic __{,test_and_}{set,clear,change}_bit() and test_bit() 



This patch introduces the C-language equivalents of the functions below:

void __set_bit(int nr, volatile unsigned long *addr);
void __clear_bit(int nr, volatile unsigned long *addr);
void __change_bit(int nr, volatile unsigned long *addr);
int __test_and_set_bit(int nr, volatile unsigned long *addr);
int __test_and_clear_bit(int nr, volatile unsigned long *addr);
int __test_and_change_bit(int nr, volatile unsigned long *addr);
int test_bit(int nr, const volatile unsigned long *addr);

In include/asm-generic/bitops/non-atomic.h

This code largely copied from: asm-powerpc/bitops.h

Signed-off-by: default avatarAkinobu Mita <mita@miraclelinux.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 7a8a2429

include/asm-generic/bitops/non-atomic.h

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#ifndef _ASM_GENERIC_BITOPS_NON_ATOMIC_H_

#define _ASM_GENERIC_BITOPS_NON_ATOMIC_H_



#include <asm/types.h>



#define BITOP_MASK(nr)		(1UL << ((nr) % BITS_PER_LONG))

#define BITOP_WORD(nr)		((nr) / BITS_PER_LONG)



/**

 * __set_bit - Set a bit in memory

 * @nr: the bit to set

 * @addr: the address to start counting from

 *

 * Unlike set_bit(), this function is non-atomic and may be reordered.

 * If it's called on the same region of memory simultaneously, the effect

 * may be that only one operation succeeds.

 */

static inline void __set_bit(int nr, volatile unsigned long *addr)

{

	unsigned long mask = BITOP_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);



	*p  |= mask;

}



static inline void __clear_bit(int nr, volatile unsigned long *addr)

{

	unsigned long mask = BITOP_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);



	*p &= ~mask;

}



/**

 * __change_bit - Toggle a bit in memory

 * @nr: the bit to change

 * @addr: the address to start counting from

 *

 * Unlike change_bit(), this function is non-atomic and may be reordered.

 * If it's called on the same region of memory simultaneously, the effect

 * may be that only one operation succeeds.

 */

static inline void __change_bit(int nr, volatile unsigned long *addr)

{

	unsigned long mask = BITOP_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);



	*p ^= mask;

}



/**

 * __test_and_set_bit - Set a bit and return its old value

 * @nr: Bit to set

 * @addr: Address to count from

 *

 * This operation is non-atomic and can be reordered.

 * If two examples of this operation race, one can appear to succeed

 * but actually fail.  You must protect multiple accesses with a lock.

 */

static inline int __test_and_set_bit(int nr, volatile unsigned long *addr)

{

	unsigned long mask = BITOP_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);

	unsigned long old = *p;



	*p = old | mask;

	return (old & mask) != 0;

}



/**

 * __test_and_clear_bit - Clear a bit and return its old value

 * @nr: Bit to clear

 * @addr: Address to count from

 *

 * This operation is non-atomic and can be reordered.

 * If two examples of this operation race, one can appear to succeed

 * but actually fail.  You must protect multiple accesses with a lock.

 */

static inline int __test_and_clear_bit(int nr, volatile unsigned long *addr)

{

	unsigned long mask = BITOP_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);

	unsigned long old = *p;



	*p = old & ~mask;

	return (old & mask) != 0;

}



/* WARNING: non atomic and it can be reordered! */

static inline int __test_and_change_bit(int nr,

					    volatile unsigned long *addr)

{

	unsigned long mask = BITOP_MASK(nr);

	unsigned long *p = ((unsigned long *)addr) + BITOP_WORD(nr);

	unsigned long old = *p;



	*p = old ^ mask;

	return (old & mask) != 0;

}



/**

 * test_bit - Determine whether a bit is set

 * @nr: bit number to test

 * @addr: Address to start counting from

 */

static inline int test_bit(int nr, const volatile unsigned long *addr)

{

	return 1UL & (addr[BITOP_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));

}



#endif /* _ASM_GENERIC_BITOPS_NON_ATOMIC_H_ */