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

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  * Copied from the kernel sources to tools/:
   4  *
   5  * Memory barrier definitions.  This is based on information published
   6  * in the Processor Abstraction Layer and the System Abstraction Layer
   7  * manual.
   8  *
   9  * Copyright (C) 1998-2003 Hewlett-Packard Co
  10  *      David Mosberger-Tang <davidm@hpl.hp.com>
  11  * Copyright (C) 1999 Asit Mallick <asit.k.mallick@intel.com>
  12  * Copyright (C) 1999 Don Dugger <don.dugger@intel.com>
  13  */
  14 #ifndef _TOOLS_LINUX_ASM_IA64_BARRIER_H
  15 #define _TOOLS_LINUX_ASM_IA64_BARRIER_H
  16
  17 #include <linux/compiler.h>
  18
  19 /*
  20  * Macros to force memory ordering.  In these descriptions, "previous"
  21  * and "subsequent" refer to program order; "visible" means that all
  22  * architecturally visible effects of a memory access have occurred
  23  * (at a minimum, this means the memory has been read or written).
  24  *
  25  *   wmb():     Guarantees that all preceding stores to memory-
  26  *              like regions are visible before any subsequent
  27  *              stores and that all following stores will be
  28  *              visible only after all previous stores.
  29  *   rmb():     Like wmb(), but for reads.
  30  *   mb():      wmb()/rmb() combo, i.e., all previous memory
  31  *              accesses are visible before all subsequent
  32  *              accesses and vice versa.  This is also known as
  33  *              a "fence."
  34  *
  35  * Note: "mb()" and its variants cannot be used as a fence to order
  36  * accesses to memory mapped I/O registers.  For that, mf.a needs to
  37  * be used.  However, we don't want to always use mf.a because (a)
  38  * it's (presumably) much slower than mf and (b) mf.a is supported for
  39  * sequential memory pages only.
  40  */
  41
  42 /* XXX From arch/ia64/include/uapi/asm/gcc_intrin.h */
  43 #define ia64_mf()       asm volatile ("mf" ::: "memory")
  44
  45 #define mb()            ia64_mf()
  46 #define rmb()           mb()
  47 #define wmb()           mb()
  48
  49 #endif /* _TOOLS_LINUX_ASM_IA64_BARRIER_H */