include/asm-i386/sync_bitops.h

   1 #ifndef _I386_SYNC_BITOPS_H
   2 #define _I386_SYNC_BITOPS_H
   3
   4 /*
   5  * Copyright 1992, Linus Torvalds.
   6  */
   7
   8 /*
   9  * These have to be done with inline assembly: that way the bit-setting
  10  * is guaranteed to be atomic. All bit operations return 0 if the bit
  11  * was cleared before the operation and != 0 if it was not.
  12  *
  13  * bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1).
  14  */
  15
  16 #define ADDR (*(volatile long *) addr)
  17
  18 /**
  19  * sync_set_bit - Atomically set a bit in memory
  20  * @nr: the bit to set
  21  * @addr: the address to start counting from
  22  *
  23  * This function is atomic and may not be reordered.  See __set_bit()
  24  * if you do not require the atomic guarantees.
  25  *
  26  * Note: there are no guarantees that this function will not be reordered
  27  * on non-x86 architectures, so if you are writing portable code,
  28  * make sure not to rely on its reordering guarantees.
  29  *
  30  * Note that @nr may be almost arbitrarily large; this function is not
  31  * restricted to acting on a single-word quantity.
  32  */
  33 static inline void sync_set_bit(int nr, volatile unsigned long * addr)
  34 {
  35         __asm__ __volatile__("lock; btsl %1,%0"
  36                              :"+m" (ADDR)
  37                              :"Ir" (nr)
  38                              : "memory");
  39 }
  40
  41 /**
  42  * sync_clear_bit - Clears a bit in memory
  43  * @nr: Bit to clear
  44  * @addr: Address to start counting from
  45  *
  46  * sync_clear_bit() is atomic and may not be reordered.  However, it does
  47  * not contain a memory barrier, so if it is used for locking purposes,
  48  * you should call smp_mb__before_clear_bit() and/or smp_mb__after_clear_bit()
  49  * in order to ensure changes are visible on other processors.
  50  */
  51 static inline void sync_clear_bit(int nr, volatile unsigned long * addr)
  52 {
  53         __asm__ __volatile__("lock; btrl %1,%0"
  54                              :"+m" (ADDR)
  55                              :"Ir" (nr)
  56                              : "memory");
  57 }
  58
  59 /**
  60  * sync_change_bit - Toggle a bit in memory
  61  * @nr: Bit to change
  62  * @addr: Address to start counting from
  63  *
  64  * change_bit() is atomic and may not be reordered. It may be
  65  * reordered on other architectures than x86.
  66  * Note that @nr may be almost arbitrarily large; this function is not
  67  * restricted to acting on a single-word quantity.
  68  */
  69 static inline void sync_change_bit(int nr, volatile unsigned long * addr)
  70 {
  71         __asm__ __volatile__("lock; btcl %1,%0"
  72                              :"+m" (ADDR)
  73                              :"Ir" (nr)
  74                              : "memory");
  75 }
  76
  77 /**
  78  * sync_test_and_set_bit - Set a bit and return its old value
  79  * @nr: Bit to set
  80  * @addr: Address to count from
  81  *
  82  * This operation is atomic and cannot be reordered.
  83  * It may be reordered on other architectures than x86.
  84  * It also implies a memory barrier.
  85  */
  86 static inline int sync_test_and_set_bit(int nr, volatile unsigned long * addr)
  87 {
  88         int oldbit;
  89
  90         __asm__ __volatile__("lock; btsl %2,%1\n\tsbbl %0,%0"
  91                              :"=r" (oldbit),"+m" (ADDR)
  92                              :"Ir" (nr) : "memory");
  93         return oldbit;
  94 }
  95
  96 /**
  97  * sync_test_and_clear_bit - Clear a bit and return its old value
  98  * @nr: Bit to clear
  99  * @addr: Address to count from
 100  *
 101  * This operation is atomic and cannot be reordered.
 102  * It can be reorderdered on other architectures other than x86.
 103  * It also implies a memory barrier.
 104  */
 105 static inline int sync_test_and_clear_bit(int nr, volatile unsigned long * addr)
 106 {
 107         int oldbit;
 108
 109         __asm__ __volatile__("lock; btrl %2,%1\n\tsbbl %0,%0"
 110                              :"=r" (oldbit),"+m" (ADDR)
 111                              :"Ir" (nr) : "memory");
 112         return oldbit;
 113 }
 114
 115 /**
 116  * sync_test_and_change_bit - Change a bit and return its old value
 117  * @nr: Bit to change
 118  * @addr: Address to count from
 119  *
 120  * This operation is atomic and cannot be reordered.
 121  * It also implies a memory barrier.
 122  */
 123 static inline int sync_test_and_change_bit(int nr, volatile unsigned long* addr)
 124 {
 125         int oldbit;
 126
 127         __asm__ __volatile__("lock; btcl %2,%1\n\tsbbl %0,%0"
 128                              :"=r" (oldbit),"+m" (ADDR)
 129                              :"Ir" (nr) : "memory");
 130         return oldbit;
 131 }
 132
 133 static __always_inline int sync_constant_test_bit(int nr, const volatile unsigned long *addr)
 134 {
 135         return ((1UL << (nr & 31)) &
 136                 (((const volatile unsigned int *)addr)[nr >> 5])) != 0;
 137 }
 138
 139 static inline int sync_var_test_bit(int nr, const volatile unsigned long * addr)
 140 {
 141         int oldbit;
 142
 143         __asm__ __volatile__("btl %2,%1\n\tsbbl %0,%0"
 144                              :"=r" (oldbit)
 145                              :"m" (ADDR),"Ir" (nr));
 146         return oldbit;
 147 }
 148
 149 #define sync_test_bit(nr,addr)                  \
 150         (__builtin_constant_p(nr) ?             \
 151          sync_constant_test_bit((nr),(addr)) :  \
 152          sync_var_test_bit((nr),(addr)))
 153
 154 #undef ADDR
 155
 156 #endif /* _I386_SYNC_BITOPS_H */