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C/C++ Source or Header  |  2006-08-11  |  2.0 KB  |  76 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.     alternative_smp("lock; subl $1,(%0)\n\t" \
  25.             "jns 1f\n" \
  26.             "call " helper "\n\t" \
  27.             "1:\n", \
  28.             "subl $1,(%0)\n\t", \
  29.             :"a" (rw) : "memory")
  30.  
  31. #define __build_read_lock_const(rw, helper)   \
  32.     alternative_smp("lock; subl $1,%0\n\t" \
  33.             "jns 1f\n" \
  34.             "pushl %%eax\n\t" \
  35.             "leal %0,%%eax\n\t" \
  36.             "call " helper "\n\t" \
  37.             "popl %%eax\n\t" \
  38.             "1:\n", \
  39.             "subl $1,%0\n\t", \
  40.             "=m" (*(volatile int *)rw) : : "memory")
  41.  
  42. #define __build_read_lock(rw, helper)    do { \
  43.                         if (__builtin_constant_p(rw)) \
  44.                             __build_read_lock_const(rw, helper); \
  45.                         else \
  46.                             __build_read_lock_ptr(rw, helper); \
  47.                     } while (0)
  48.  
  49. #define __build_write_lock_ptr(rw, helper) \
  50.     alternative_smp("lock; subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
  51.             "jz 1f\n" \
  52.             "call " helper "\n\t" \
  53.             "1:\n", \
  54.             "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t", \
  55.             :"a" (rw) : "memory")
  56.  
  57. #define __build_write_lock_const(rw, helper) \
  58.     alternative_smp("lock; subl $" RW_LOCK_BIAS_STR ",%0\n\t" \
  59.             "jz 1f\n" \
  60.             "pushl %%eax\n\t" \
  61.             "leal %0,%%eax\n\t" \
  62.             "call " helper "\n\t" \
  63.             "popl %%eax\n\t" \
  64.             "1:\n", \
  65.             "subl $" RW_LOCK_BIAS_STR ",%0\n\t", \
  66.             "=m" (*(volatile int *)rw) : : "memory")
  67.  
  68. #define __build_write_lock(rw, helper)    do { \
  69.                         if (__builtin_constant_p(rw)) \
  70.                             __build_write_lock_const(rw, helper); \
  71.                         else \
  72.                             __build_write_lock_ptr(rw, helper); \
  73.                     } while (0)
  74.  
  75. #endif
  76.