tools/arch/ia64/include/asm/barrier.h

   1 /*
   2  * Copied from the kernel sources to tools/:
   3  *
   4  * Memory barrier definitions.  This is based on information published
   5  * in the Processor Abstraction Layer and the System Abstraction Layer
   6  * manual.
   7  *
   8  * Copyright (C) 1998-2003 Hewlett-Packard Co
   9  *      David Mosberger-Tang <davidm@hpl.hp.com>
  10  * Copyright (C) 1999 Asit Mallick <asit.k.mallick@intel.com>
  11  * Copyright (C) 1999 Don Dugger <don.dugger@intel.com>
  12  */
  13 #ifndef _TOOLS_LINUX_ASM_IA64_BARRIER_H
  14 #define _TOOLS_LINUX_ASM_IA64_BARRIER_H
  15
  16 #include <linux/compiler.h>
  17
  18 /*
  19  * Macros to force memory ordering.  In these descriptions, "previous"
  20  * and "subsequent" refer to program order; "visible" means that all
  21  * architecturally visible effects of a memory access have occurred
  22  * (at a minimum, this means the memory has been read or written).
  23  *
  24  *   wmb():     Guarantees that all preceding stores to memory-
  25  *              like regions are visible before any subsequent
  26  *              stores and that all following stores will be
  27  *              visible only after all previous stores.
  28  *   rmb():     Like wmb(), but for reads.
  29  *   mb():      wmb()/rmb() combo, i.e., all previous memory
  30  *              accesses are visible before all subsequent
  31  *              accesses and vice versa.  This is also known as
  32  *              a "fence."
  33  *
  34  * Note: "mb()" and its variants cannot be used as a fence to order
  35  * accesses to memory mapped I/O registers.  For that, mf.a needs to
  36  * be used.  However, we don't want to always use mf.a because (a)
  37  * it's (presumably) much slower than mf and (b) mf.a is supported for
  38  * sequential memory pages only.
  39  */
  40
  41 /* XXX From arch/ia64/include/uapi/asm/gcc_intrin.h */
  42 #define ia64_mf()       asm volatile ("mf" ::: "memory")
  43
  44 #define mb()            ia64_mf()
  45 #define rmb()           mb()
  46 #define wmb()           mb()
  47
  48 #endif /* _TOOLS_LINUX_ASM_IA64_BARRIER_H */