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 #define smp_mb()        mb()
  59 #define smp_rmb()       rmb()
  60 #define smp_wmb()       wmb()
  61 #define smp_read_barrier_depends()      read_barrier_depends()
  62 #else
  63 #define smp_mb()        barrier()
  64 #define smp_rmb()       barrier()
  65 #define smp_wmb()       barrier()
  66 #define smp_read_barrier_depends()      do { } while (0)
  67 #endif
  68
  69 #ifndef set_mb
  70 #define set_mb(var, value)  do { (var) = (value); mb(); } while (0)
  71 #endif
  72
  73 #ifndef smp_mb__before_atomic
  74 #define smp_mb__before_atomic() smp_mb()
  75 #endif
  76
  77 #ifndef smp_mb__after_atomic
  78 #define smp_mb__after_atomic()  smp_mb()
  79 #endif
  80
  81 #define smp_store_release(p, v)                                         \
  82 do {                                                                    \
  83         compiletime_assert_atomic_type(*p);                             \
  84         smp_mb();                                                       \
  85         ACCESS_ONCE(*p) = (v);                                          \
  86 } while (0)
  87
  88 #define smp_load_acquire(p)                                             \
  89 ({                                                                      \
  90         typeof(*p) ___p1 = ACCESS_ONCE(*p);                             \
  91         compiletime_assert_atomic_type(*p);                             \
  92         smp_mb();                                                       \
  93         ___p1;                                                          \
  94 })
  95
  96 #endif /* !__ASSEMBLY__ */
  97 #endif /* __ASM_GENERIC_BARRIER_H */