From 4117b02132d1cf96a3e1c57148e302c4801c974d Mon Sep 17 00:00:00 2001 From: Akinobu Mita Date: Sun, 26 Mar 2006 01:39:07 -0800 Subject: [PATCH] [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: Akinobu Mita Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/asm-generic/bitops/non-atomic.h | 111 ++++++++++++++++++++++++ 1 file changed, 111 insertions(+) create mode 100644 include/asm-generic/bitops/non-atomic.h diff --git a/include/asm-generic/bitops/non-atomic.h b/include/asm-generic/bitops/non-atomic.h new file mode 100644 index 00000000000..46a825cf2ae --- /dev/null +++ b/include/asm-generic/bitops/non-atomic.h @@ -0,0 +1,111 @@ +#ifndef _ASM_GENERIC_BITOPS_NON_ATOMIC_H_ +#define _ASM_GENERIC_BITOPS_NON_ATOMIC_H_ + +#include + +#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_ */