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

   1#ifndef _ASM_GENERIC_BITOPS_NON_ATOMIC_H_
   2#define _ASM_GENERIC_BITOPS_NON_ATOMIC_H_
   3
   4#include <asm/types.h>
   5
   6/**
   7 * __set_bit - Set a bit in memory
   8 * @nr: the bit to set
   9 * @addr: the address to start counting from
  10 *
  11 * Unlike set_bit(), this function is non-atomic and may be reordered.
  12 * If it's called on the same region of memory simultaneously, the effect
  13 * may be that only one operation succeeds.
  14 */
  15static inline void __set_bit(int nr, volatile unsigned long *addr)
  16{
  17        unsigned long mask = BIT_MASK(nr);
  18        unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
  19
  20        *p  |= mask;
  21}
  22
  23static inline void __clear_bit(int nr, volatile unsigned long *addr)
  24{
  25        unsigned long mask = BIT_MASK(nr);
  26        unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
  27
  28        *p &= ~mask;
  29}
  30
  31/**
  32 * __change_bit - Toggle a bit in memory
  33 * @nr: the bit to change
  34 * @addr: the address to start counting from
  35 *
  36 * Unlike change_bit(), this function is non-atomic and may be reordered.
  37 * If it's called on the same region of memory simultaneously, the effect
  38 * may be that only one operation succeeds.
  39 */
  40static inline void __change_bit(int nr, volatile unsigned long *addr)
  41{
  42        unsigned long mask = BIT_MASK(nr);
  43        unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
  44
  45        *p ^= mask;
  46}
  47
  48/**
  49 * __test_and_set_bit - Set a bit and return its old value
  50 * @nr: Bit to set
  51 * @addr: Address to count from
  52 *
  53 * This operation is non-atomic and can be reordered.
  54 * If two examples of this operation race, one can appear to succeed
  55 * but actually fail.  You must protect multiple accesses with a lock.
  56 */
  57static inline int __test_and_set_bit(int nr, volatile unsigned long *addr)
  58{
  59        unsigned long mask = BIT_MASK(nr);
  60        unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
  61        unsigned long old = *p;
  62
  63        *p = old | mask;
  64        return (old & mask) != 0;
  65}
  66
  67/**
  68 * __test_and_clear_bit - Clear a bit and return its old value
  69 * @nr: Bit to clear
  70 * @addr: Address to count from
  71 *
  72 * This operation is non-atomic and can be reordered.
  73 * If two examples of this operation race, one can appear to succeed
  74 * but actually fail.  You must protect multiple accesses with a lock.
  75 */
  76static inline int __test_and_clear_bit(int nr, volatile unsigned long *addr)
  77{
  78        unsigned long mask = BIT_MASK(nr);
  79        unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
  80        unsigned long old = *p;
  81
  82        *p = old & ~mask;
  83        return (old & mask) != 0;
  84}
  85
  86/* WARNING: non atomic and it can be reordered! */
  87static inline int __test_and_change_bit(int nr,
  88                                            volatile unsigned long *addr)
  89{
  90        unsigned long mask = BIT_MASK(nr);
  91        unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
  92        unsigned long old = *p;
  93
  94        *p = old ^ mask;
  95        return (old & mask) != 0;
  96}
  97
  98/**
  99 * test_bit - Determine whether a bit is set
 100 * @nr: bit number to test
 101 * @addr: Address to start counting from
 102 */
 103static inline int test_bit(int nr, const volatile unsigned long *addr)
 104{
 105        return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
 106}
 107
 108#endif /* _ASM_GENERIC_BITOPS_NON_ATOMIC_H_ */
 109