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

INCLUDED FROM

DEFINITIONS

1. __set_bit
2. __clear_bit
3. __change_bit
4. __test_and_set_bit
5. __test_and_clear_bit
6. __test_and_change_bit
7. test_bit

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef _ASM_GENERIC_BITOPS_NON_ATOMIC_H_
   3 #define _ASM_GENERIC_BITOPS_NON_ATOMIC_H_
   4 
   5 #include <asm/types.h>
   6 
   7 /**
   8  * __set_bit - Set a bit in memory
   9  * @nr: the bit to set
  10  * @addr: the address to start counting from
  11  *
  12  * Unlike set_bit(), this function is non-atomic and may be reordered.
  13  * If it's called on the same region of memory simultaneously, the effect
  14  * may be that only one operation succeeds.
  15  */
  16 static inline void __set_bit(int nr, volatile unsigned long *addr)
  17 {
  18         unsigned long mask = BIT_MASK(nr);
  19         unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
  20 
  21         *p  |= mask;
  22 }
  23 
  24 static inline void __clear_bit(int nr, volatile unsigned long *addr)
  25 {
  26         unsigned long mask = BIT_MASK(nr);
  27         unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
  28 
  29         *p &= ~mask;
  30 }
  31 
  32 /**
  33  * __change_bit - Toggle a bit in memory
  34  * @nr: the bit to change
  35  * @addr: the address to start counting from
  36  *
  37  * Unlike change_bit(), this function is non-atomic and may be reordered.
  38  * If it's called on the same region of memory simultaneously, the effect
  39  * may be that only one operation succeeds.
  40  */
  41 static inline void __change_bit(int nr, volatile unsigned long *addr)
  42 {
  43         unsigned long mask = BIT_MASK(nr);
  44         unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
  45 
  46         *p ^= mask;
  47 }
  48 
  49 /**
  50  * __test_and_set_bit - Set a bit and return its old value
  51  * @nr: Bit to set
  52  * @addr: Address to count from
  53  *
  54  * This operation is non-atomic and can be reordered.
  55  * If two examples of this operation race, one can appear to succeed
  56  * but actually fail.  You must protect multiple accesses with a lock.
  57  */
  58 static inline int __test_and_set_bit(int nr, volatile unsigned long *addr)
  59 {
  60         unsigned long mask = BIT_MASK(nr);
  61         unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
  62         unsigned long old = *p;
  63 
  64         *p = old | mask;
  65         return (old & mask) != 0;
  66 }
  67 
  68 /**
  69  * __test_and_clear_bit - Clear a bit and return its old value
  70  * @nr: Bit to clear
  71  * @addr: Address to count from
  72  *
  73  * This operation is non-atomic and can be reordered.
  74  * If two examples of this operation race, one can appear to succeed
  75  * but actually fail.  You must protect multiple accesses with a lock.
  76  */
  77 static inline int __test_and_clear_bit(int nr, volatile unsigned long *addr)
  78 {
  79         unsigned long mask = BIT_MASK(nr);
  80         unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
  81         unsigned long old = *p;
  82 
  83         *p = old & ~mask;
  84         return (old & mask) != 0;
  85 }
  86 
  87 /* WARNING: non atomic and it can be reordered! */
  88 static inline int __test_and_change_bit(int nr,
  89                                             volatile unsigned long *addr)
  90 {
  91         unsigned long mask = BIT_MASK(nr);
  92         unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
  93         unsigned long old = *p;
  94 
  95         *p = old ^ mask;
  96         return (old & mask) != 0;
  97 }
  98 
  99 /**
 100  * test_bit - Determine whether a bit is set
 101  * @nr: bit number to test
 102  * @addr: Address to start counting from
 103  */
 104 static inline int test_bit(int nr, const volatile unsigned long *addr)
 105 {
 106         return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
 107 }
 108 
 109 #endif /* _ASM_GENERIC_BITOPS_NON_ATOMIC_H_ */