pt-machine.h 3.9 KB

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  1. /* Machine-dependent pthreads configuration and inline functions.
  2. i386 version.
  3. Copyright (C) 1996-2001, 2002 Free Software Foundation, Inc.
  4. This file is part of the GNU C Library.
  5. Contributed by Richard Henderson <rth@tamu.edu>.
  6. The GNU C Library is free software; you can redistribute it and/or
  7. modify it under the terms of the GNU Lesser General Public License as
  8. published by the Free Software Foundation; either version 2.1 of the
  9. License, or (at your option) any later version.
  10. The GNU C Library is distributed in the hope that it will be useful,
  11. but WITHOUT ANY WARRANTY; without even the implied warranty of
  12. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  13. Lesser General Public License for more details.
  14. You should have received a copy of the GNU Lesser General Public
  15. License along with the GNU C Library; see the file COPYING.LIB. If not,
  16. write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17. Boston, MA 02111-1307, USA. */
  18. #ifndef _PT_MACHINE_H
  19. #define _PT_MACHINE_H 1
  20. #ifndef __ASSEMBLER__
  21. #ifndef PT_EI
  22. # define PT_EI extern inline
  23. #endif
  24. extern long int testandset (int *spinlock);
  25. extern int __compare_and_swap (long int *p, long int oldval, long int newval);
  26. /* Get some notion of the current stack. Need not be exactly the top
  27. of the stack, just something somewhere in the current frame. */
  28. #define CURRENT_STACK_FRAME __builtin_frame_address (0)
  29. /* See if we can optimize for newer cpus... */
  30. #if defined __GNUC__ && __GNUC__ >= 2 && defined __i486__ || defined __pentium__ || defined __pentiumpro__
  31. /* Spinlock implementation; required. */
  32. PT_EI long int
  33. testandset (int *spinlock)
  34. {
  35. long int ret;
  36. __asm__ __volatile__ (
  37. "xchgl %0, %1"
  38. : "=r" (ret), "=m" (*spinlock)
  39. : "0" (1), "m" (*spinlock)
  40. : "memory");
  41. return ret;
  42. }
  43. /* Compare-and-swap for semaphores. It's always available on i686. */
  44. #define HAS_COMPARE_AND_SWAP
  45. PT_EI int
  46. __compare_and_swap (long int *p, long int oldval, long int newval)
  47. {
  48. char ret;
  49. long int readval;
  50. __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
  51. : "=q" (ret), "=m" (*p), "=a" (readval)
  52. : "r" (newval), "m" (*p), "a" (oldval)
  53. : "memory");
  54. return ret;
  55. }
  56. #if __ASSUME_LDT_WORKS > 0
  57. #include "../useldt.h"
  58. #endif
  59. /* The P4 and above really want some help to prevent overheating. */
  60. #define BUSY_WAIT_NOP __asm__ ("rep; nop")
  61. #else /* Generic i386 implementation */
  62. /* Spinlock implementation; required. */
  63. PT_EI long int
  64. testandset (int *spinlock)
  65. {
  66. long int ret;
  67. __asm__ __volatile__(
  68. "xchgl %0, %1"
  69. : "=r"(ret), "=m"(*spinlock)
  70. : "0"(1), "m"(*spinlock)
  71. : "memory");
  72. return ret;
  73. }
  74. /* Compare-and-swap for semaphores.
  75. Available on the 486 and above, but not on the 386.
  76. We test dynamically whether it's available or not. */
  77. #define HAS_COMPARE_AND_SWAP
  78. #define TEST_FOR_COMPARE_AND_SWAP
  79. PT_EI int
  80. __compare_and_swap (long int *p, long int oldval, long int newval)
  81. {
  82. char ret;
  83. long int readval;
  84. __asm__ __volatile__ ("lock; cmpxchgl %3, %1; sete %0"
  85. : "=q" (ret), "=m" (*p), "=a" (readval)
  86. : "r" (newval), "m" (*p), "a" (oldval)
  87. : "memory");
  88. return ret;
  89. }
  90. PT_EI int
  91. get_eflags (void)
  92. {
  93. int res;
  94. __asm__ __volatile__ ("pushfl; popl %0" : "=r" (res) : );
  95. return res;
  96. }
  97. PT_EI void
  98. set_eflags (int newflags)
  99. {
  100. __asm__ __volatile__ ("pushl %0; popfl" : : "r" (newflags) : "cc");
  101. }
  102. PT_EI int
  103. compare_and_swap_is_available (void)
  104. {
  105. int oldflags = get_eflags ();
  106. int changed;
  107. /* Flip AC bit in EFLAGS. */
  108. set_eflags (oldflags ^ 0x40000);
  109. /* See if bit changed. */
  110. changed = (get_eflags () ^ oldflags) & 0x40000;
  111. /* Restore EFLAGS. */
  112. set_eflags (oldflags);
  113. /* If the AC flag did not change, it's a 386 and it lacks cmpxchg.
  114. Otherwise, it's a 486 or above and it has cmpxchg. */
  115. return changed != 0;
  116. }
  117. #endif /* Generic i386 implementation */
  118. #endif /* __ASSEMBLER__ */
  119. #endif /* pt-machine.h */