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C/C++ Source or Header  |  2006-08-11  |  2.4 KB  |  87 lines
  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. #include <linux/stringify.h>
  22.  
  23. #define RW_LOCK_BIAS         0x01000000
  24. #define RW_LOCK_BIAS_STR    "0x01000000"
  25.  
  26. #define __build_read_lock_ptr(rw, helper)   \
  27.     asm volatile(LOCK_PREFIX "subl $1,(%0)\n\t" \
  28.              "js 2f\n" \
  29.              "1:\n" \
  30.             LOCK_SECTION_START("") \
  31.              "2:\tcall " helper "\n\t" \
  32.              "jmp 1b\n" \
  33.             LOCK_SECTION_END \
  34.              ::"a" (rw) : "memory")
  35.  
  36. #define __build_read_lock_const(rw, helper)   \
  37.     asm volatile(LOCK_PREFIX "subl $1,%0\n\t" \
  38.              "js 2f\n" \
  39.              "1:\n" \
  40.             LOCK_SECTION_START("") \
  41.              "2:\tpushq %%rax\n\t" \
  42.              "leaq %0,%%rax\n\t" \
  43.              "call " helper "\n\t" \
  44.              "popq %%rax\n\t" \
  45.              "jmp 1b\n" \
  46.             LOCK_SECTION_END \
  47.              :"=m" (*((volatile int *)rw))::"memory")
  48.  
  49. #define __build_read_lock(rw, helper)    do { \
  50.                         if (__builtin_constant_p(rw)) \
  51.                             __build_read_lock_const(rw, helper); \
  52.                         else \
  53.                             __build_read_lock_ptr(rw, helper); \
  54.                     } while (0)
  55.  
  56. #define __build_write_lock_ptr(rw, helper) \
  57.     asm volatile(LOCK_PREFIX "subl $" RW_LOCK_BIAS_STR ",(%0)\n\t" \
  58.              "jnz 2f\n" \
  59.              "1:\n" \
  60.              LOCK_SECTION_START("") \
  61.              "2:\tcall " helper "\n\t" \
  62.              "jmp 1b\n" \
  63.              LOCK_SECTION_END \
  64.              ::"a" (rw) : "memory")
  65.  
  66. #define __build_write_lock_const(rw, helper) \
  67.     asm volatile(LOCK_PREFIX "subl $" RW_LOCK_BIAS_STR ",%0\n\t" \
  68.              "jnz 2f\n" \
  69.              "1:\n" \
  70.             LOCK_SECTION_START("") \
  71.              "2:\tpushq %%rax\n\t" \
  72.              "leaq %0,%%rax\n\t" \
  73.              "call " helper "\n\t" \
  74.              "popq %%rax\n\t" \
  75.              "jmp 1b\n" \
  76.             LOCK_SECTION_END \
  77.              :"=m" (*((volatile long *)rw))::"memory")
  78.  
  79. #define __build_write_lock(rw, helper)    do { \
  80.                         if (__builtin_constant_p(rw)) \
  81.                             __build_write_lock_const(rw, helper); \
  82.                         else \
  83.                             __build_write_lock_ptr(rw, helper); \
  84.                     } while (0)
  85.  
  86. #endif
  87.