arch/x86/include/asm/sync_bitops.h

   1 #ifndef _ASM_X86_SYNC_BITOPS_H
   2 #define _ASM_X86_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 that @nr may be almost arbitrarily large; this function is not
  27  * restricted to acting on a single-word quantity.
  28  */
  29 static inline void sync_set_bit(long nr, volatile unsigned long *addr)
  30 {
  31         asm volatile("lock; bts %1,%0"
  32                      : "+m" (ADDR)
  33                      : "Ir" (nr)
  34                      : "memory");
  35 }
  36
  37 /**
  38  * sync_clear_bit - Clears a bit in memory
  39  * @nr: Bit to clear
  40  * @addr: Address to start counting from
  41  *
  42  * sync_clear_bit() is atomic and may not be reordered.  However, it does
  43  * not contain a memory barrier, so if it is used for locking purposes,
  44  * you should call smp_mb__before_atomic() and/or smp_mb__after_atomic()
  45  * in order to ensure changes are visible on other processors.
  46  */
  47 static inline void sync_clear_bit(long nr, volatile unsigned long *addr)
  48 {
  49         asm volatile("lock; btr %1,%0"
  50                      : "+m" (ADDR)
  51                      : "Ir" (nr)
  52                      : "memory");
  53 }
  54
  55 /**
  56  * sync_change_bit - Toggle a bit in memory
  57  * @nr: Bit to change
  58  * @addr: Address to start counting from
  59  *
  60  * sync_change_bit() is atomic and may not be reordered.
  61  * Note that @nr may be almost arbitrarily large; this function is not
  62  * restricted to acting on a single-word quantity.
  63  */
  64 static inline void sync_change_bit(long nr, volatile unsigned long *addr)
  65 {
  66         asm volatile("lock; btc %1,%0"
  67                      : "+m" (ADDR)
  68                      : "Ir" (nr)
  69                      : "memory");
  70 }
  71
  72 /**
  73  * sync_test_and_set_bit - Set a bit and return its old value
  74  * @nr: Bit to set
  75  * @addr: Address to count from
  76  *
  77  * This operation is atomic and cannot be reordered.
  78  * It also implies a memory barrier.
  79  */
  80 static inline int sync_test_and_set_bit(long nr, volatile unsigned long *addr)
  81 {
  82         int oldbit;
  83
  84         asm volatile("lock; bts %2,%1\n\tsbbl %0,%0"
  85                      : "=r" (oldbit), "+m" (ADDR)
  86                      : "Ir" (nr) : "memory");
  87         return oldbit;
  88 }
  89
  90 /**
  91  * sync_test_and_clear_bit - Clear a bit and return its old value
  92  * @nr: Bit to clear
  93  * @addr: Address to count from
  94  *
  95  * This operation is atomic and cannot be reordered.
  96  * It also implies a memory barrier.
  97  */
  98 static inline int sync_test_and_clear_bit(long nr, volatile unsigned long *addr)
  99 {
 100         int oldbit;
 101
 102         asm volatile("lock; btr %2,%1\n\tsbbl %0,%0"
 103                      : "=r" (oldbit), "+m" (ADDR)
 104                      : "Ir" (nr) : "memory");
 105         return oldbit;
 106 }
 107
 108 /**
 109  * sync_test_and_change_bit - Change a bit and return its old value
 110  * @nr: Bit to change
 111  * @addr: Address to count from
 112  *
 113  * This operation is atomic and cannot be reordered.
 114  * It also implies a memory barrier.
 115  */
 116 static inline int sync_test_and_change_bit(long nr, volatile unsigned long *addr)
 117 {
 118         int oldbit;
 119
 120         asm volatile("lock; btc %2,%1\n\tsbbl %0,%0"
 121                      : "=r" (oldbit), "+m" (ADDR)
 122                      : "Ir" (nr) : "memory");
 123         return oldbit;
 124 }
 125
 126 #define sync_test_bit(nr, addr) test_bit(nr, addr)
 127
 128 #undef ADDR
 129
 130 #endif /* _ASM_X86_SYNC_BITOPS_H */