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kernel/linux-rt-4.4.41/tools/arch/powerpc/include/asm/barrier.h 1.11 KB
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  /*
   * Copied from the kernel sources:
   *
   * Copyright (C) 1999 Cort Dougan <cort@cs.nmt.edu>
   */
  #ifndef _TOOLS_LINUX_ASM_POWERPC_BARRIER_H
  #define _TOOLS_LINUX_ASM_POWERPC_BARRIER_H
  
  /*
   * Memory barrier.
   * The sync instruction guarantees that all memory accesses initiated
   * by this processor have been performed (with respect to all other
   * mechanisms that access memory).  The eieio instruction is a barrier
   * providing an ordering (separately) for (a) cacheable stores and (b)
   * loads and stores to non-cacheable memory (e.g. I/O devices).
   *
   * mb() prevents loads and stores being reordered across this point.
   * rmb() prevents loads being reordered across this point.
   * wmb() prevents stores being reordered across this point.
   *
   * *mb() variants without smp_ prefix must order all types of memory
   * operations with one another. sync is the only instruction sufficient
   * to do this.
   */
  #define mb()   __asm__ __volatile__ ("sync" : : : "memory")
  #define rmb()  __asm__ __volatile__ ("sync" : : : "memory")
  #define wmb()  __asm__ __volatile__ ("sync" : : : "memory")
  
  #endif /* _TOOLS_LINUX_ASM_POWERPC_BARRIER_H */