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   1 /* include/asm-x86_64/rwlock.h
   2  *
   3  *      Helpers used by both rw spinlocks and rw semaphores.
   4  *
   5  *      Based in part on code from semaphore.h and
   6  *      spinlock.h Copyright 1996 Linus Torvalds.
   7  *
   8  *      Copyright 1999 Red Hat, Inc.
   9  *      Copyright 2001,2002 SuSE labs
  10  *
  11  *      Written by Benjamin LaHaise.
  12  *
  13  *      This program is free software; you can redistribute it and/or
  14  *      modify it under the terms of the GNU General Public License
  15  *      as published by the Free Software Foundation; either version
  16  *      2 of the License, or (at your option) any later version.
  17  */
  18 #ifndef _ASM_X86_64_RWLOCK_H
  19 #define _ASM_X86_64_RWLOCK_H
  20
  21 #define RW_LOCK_BIAS             0x01000000
  22 #define RW_LOCK_BIAS_STR         "0x01000000"
  23
  24 #define __build_read_lock(rw)   \
  25         asm volatile(LOCK_PREFIX "subl $1,(%0)\n\t" \
  26                      "jns 1f\n" \
  27                      "call __read_lock_failed\n" \
  28                      "1:\n" \
  29                      ::"D" (rw), "i" (RW_LOCK_BIAS) : "memory")
  30
  31 #define __build_write_lock(rw) \
  32         asm volatile(LOCK_PREFIX "subl %1,(%0)\n\t" \
  33                      "jz 1f\n" \
  34                      "\tcall __write_lock_failed\n\t" \
  35                      "1:\n" \
  36                      ::"D" (rw), "i" (RW_LOCK_BIAS) : "memory")
  37
  38 #endif