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C/C++ Source or Header  |  2005-10-13  |  2KB  |  72 lines
  1. /* include/asm-i386/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.  *
  10.  *    Written by Benjamin LaHaise.
  11.  *
  12.  *    This program is free software; you can redistribute it and/or
  13.  *    modify it under the terms of the GNU General Public License
  14.  *    as published by the Free Software Foundation; either version
  15.  *    2 of the License, or (at your option) any later version.
  16.  */
  17. #ifndef _ASM_I386_RWLOCK_H
  18. #define _ASM_I386_RWLOCK_H
  19.  
  20. #define RW_LOCK_BIAS         0x01000000
  21. #define RW_LOCK_BIAS_STR    "0x01000000"
  22.  
  23. #define __build_read_lock_ptr(rw, helper)   \
  24.     asm volatile(LOCK "subl $1,(%0)\n\t" \
  25.              "jns 1f\n" \
  26.              "call " helper "\n\t" \
  27.              "1:\n" \
  28.              ::"a" (rw) : "memory")
  29.  
  30. #define __build_read_lock_const(rw, helper)   \
  31.     asm volatile(LOCK "subl $1,%0\n\t" \
  32.              "jns 1f\n" \
  33.              "pushl %%eax\n\t" \
  34.              "leal %0,%%eax\n\t" \
  35.              "call " helper "\n\t" \
  36.              "popl %%eax\n\t" \
  37.              "1:\n" \
  38.              :"=m" (*(volatile int *)rw) : : "memory")
  39.  
  40. #define __build_read_lock(rw, helper)    do { \
  41.                         if (__builtin_constant_p(rw)) \
  42.                             __build_read_lock_const(rw, helper); \
  43.                         else \
  44.                             __build_read_lock_ptr(rw, helper); \
  45.                     } while (0)
  46.  
  47. #define __build_write_lock_ptr(rw, helper) \
  48.     asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
  49.              "jz 1f\n" \
  50.              "call " helper "\n\t" \
  51.              "1:\n" \
  52.              ::"a" (rw) : "memory")
  53.  
  54. #define __build_write_lock_const(rw, helper) \
  55.     asm volatile(LOCK "subl $" RW_LOCK_BIAS_STR ",%0\n\t" \
  56.              "jz 1f\n" \
  57.              "pushl %%eax\n\t" \
  58.              "leal %0,%%eax\n\t" \
  59.              "call " helper "\n\t" \
  60.              "popl %%eax\n\t" \
  61.              "1:\n" \
  62.              :"=m" (*(volatile int *)rw) : : "memory")
  63.  
  64. #define __build_write_lock(rw, helper)    do { \
  65.                         if (__builtin_constant_p(rw)) \
  66.                             __build_write_lock_const(rw, helper); \
  67.                         else \
  68.                             __build_write_lock_ptr(rw, helper); \
  69.                     } while (0)
  70.  
  71. #endif
  72.