include/asm-generic/barrier.h

   1 /* Generic barrier definitions, based on MN10300 definitions.
   2  *
   3  * It should be possible to use these on really simple architectures,
   4  * but it serves more as a starting point for new ports.
   5  *
   6  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
   7  * Written by David Howells (dhowells@redhat.com)
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public Licence
  11  * as published by the Free Software Foundation; either version
  12  * 2 of the Licence, or (at your option) any later version.
  13  */
  14 #ifndef __ASM_GENERIC_BARRIER_H
  15 #define __ASM_GENERIC_BARRIER_H
  16
  17 #ifndef __ASSEMBLY__
  18
  19 #define nop() asm volatile ("nop")
  20
  21 /*
  22  * Force strict CPU ordering.
  23  * And yes, this is required on UP too when we're talking
  24  * to devices.
  25  *
  26  * This implementation only contains a compiler barrier.
  27  */
  28
  29 #define mb()    asm volatile ("": : :"memory")
  30 #define rmb()   mb()
  31 #define wmb()   asm volatile ("": : :"memory")
  32
  33 #ifdef CONFIG_SMP
  34 #define smp_mb()        mb()
  35 #define smp_rmb()       rmb()
  36 #define smp_wmb()       wmb()
  37 #else
  38 #define smp_mb()        barrier()
  39 #define smp_rmb()       barrier()
  40 #define smp_wmb()       barrier()
  41 #endif
  42
  43 #define set_mb(var, value)  do { var = value;  mb(); } while (0)
  44 #define set_wmb(var, value) do { var = value; wmb(); } while (0)
  45
  46 #define read_barrier_depends()          do {} while (0)
  47 #define smp_read_barrier_depends()      do {} while (0)
  48
  49 #endif /* !__ASSEMBLY__ */
  50 #endif /* __ASM_GENERIC_BARRIER_H */