include/asm-generic/barrier.h

   1 /*
   2  * Generic barrier definitions, originally based on MN10300 definitions.
   3  *
   4  * It should be possible to use these on really simple architectures,
   5  * but it serves more as a starting point for new ports.
   6  *
   7  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   8  * Written by David Howells (dhowells@redhat.com)
   9  *
  10  * This program is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU General Public Licence
  12  * as published by the Free Software Foundation; either version
  13  * 2 of the Licence, or (at your option) any later version.
  14  */
  15 #ifndef __ASM_GENERIC_BARRIER_H
  16 #define __ASM_GENERIC_BARRIER_H
  17
  18 #ifndef __ASSEMBLY__
  19
  20 #include <linux/compiler.h>
  21
  22 #ifndef nop
  23 #define nop()   asm volatile ("nop")
  24 #endif
  25
  26 /*
  27  * Force strict CPU ordering. And yes, this is required on UP too when we're
  28  * talking to devices.
  29  *
  30  * Fall back to compiler barriers if nothing better is provided.
  31  */
  32
  33 #ifndef mb
  34 #define mb()    barrier()
  35 #endif
  36
  37 #ifndef rmb
  38 #define rmb()   mb()
  39 #endif
  40
  41 #ifndef wmb
  42 #define wmb()   mb()
  43 #endif
  44
  45 #ifndef dma_rmb
  46 #define dma_rmb()       rmb()
  47 #endif
  48
  49 #ifndef dma_wmb
  50 #define dma_wmb()       wmb()
  51 #endif
  52
  53 #ifndef read_barrier_depends
  54 #define read_barrier_depends()          do { } while (0)
  55 #endif
  56
  57 #ifdef CONFIG_SMP
  58
  59 #ifndef smp_mb
  60 #define smp_mb()        mb()
  61 #endif
  62
  63 #ifndef smp_rmb
  64 #define smp_rmb()       rmb()
  65 #endif
  66
  67 #ifndef smp_wmb
  68 #define smp_wmb()       wmb()
  69 #endif
  70
  71 #ifndef smp_read_barrier_depends
  72 #define smp_read_barrier_depends()      read_barrier_depends()
  73 #endif
  74
  75 #else   /* !CONFIG_SMP */
  76
  77 #ifndef smp_mb
  78 #define smp_mb()        barrier()
  79 #endif
  80
  81 #ifndef smp_rmb
  82 #define smp_rmb()       barrier()
  83 #endif
  84
  85 #ifndef smp_wmb
  86 #define smp_wmb()       barrier()
  87 #endif
  88
  89 #ifndef smp_read_barrier_depends
  90 #define smp_read_barrier_depends()      do { } while (0)
  91 #endif
  92
  93 #endif  /* CONFIG_SMP */
  94
  95 #ifndef smp_store_mb
  96 #define smp_store_mb(var, value)  do { WRITE_ONCE(var, value); smp_mb(); } while (0)
  97 #endif
  98
  99 #ifndef smp_mb__before_atomic
 100 #define smp_mb__before_atomic() smp_mb()
 101 #endif
 102
 103 #ifndef smp_mb__after_atomic
 104 #define smp_mb__after_atomic()  smp_mb()
 105 #endif
 106
 107 #define smp_store_release(p, v)                                         \
 108 do {                                                                    \
 109         compiletime_assert_atomic_type(*p);                             \
 110         smp_mb();                                                       \
 111         WRITE_ONCE(*p, v);                                              \
 112 } while (0)
 113
 114 #define smp_load_acquire(p)                                             \
 115 ({                                                                      \
 116         typeof(*p) ___p1 = READ_ONCE(*p);                               \
 117         compiletime_assert_atomic_type(*p);                             \
 118         smp_mb();                                                       \
 119         ___p1;                                                          \
 120 })
 121
 122 #endif /* !__ASSEMBLY__ */
 123 #endif /* __ASM_GENERIC_BARRIER_H */