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 read_barrier_depends
  46 #define read_barrier_depends()          do { } while (0)
  47 #endif
  48
  49 #ifdef CONFIG_SMP
  50 #define smp_mb()        mb()
  51 #define smp_rmb()       rmb()
  52 #define smp_wmb()       wmb()
  53 #define smp_read_barrier_depends()      read_barrier_depends()
  54 #else
  55 #define smp_mb()        barrier()
  56 #define smp_rmb()       barrier()
  57 #define smp_wmb()       barrier()
  58 #define smp_read_barrier_depends()      do { } while (0)
  59 #endif
  60
  61 #ifndef set_mb
  62 #define set_mb(var, value)  do { (var) = (value); mb(); } while (0)
  63 #endif
  64
  65 #define smp_store_release(p, v)                                         \
  66 do {                                                                    \
  67         compiletime_assert_atomic_type(*p);                             \
  68         smp_mb();                                                       \
  69         ACCESS_ONCE(*p) = (v);                                          \
  70 } while (0)
  71
  72 #define smp_load_acquire(p)                                             \
  73 ({                                                                      \
  74         typeof(*p) ___p1 = ACCESS_ONCE(*p);                             \
  75         compiletime_assert_atomic_type(*p);                             \
  76         smp_mb();                                                       \
  77         ___p1;                                                          \
  78 })
  79
  80 #endif /* !__ASSEMBLY__ */
  81 #endif /* __ASM_GENERIC_BARRIER_H */