pthread_cancel.c 3.4 KB

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  1. /* Copyright (C) 2002, 2003, 2004, 2009 Free Software Foundation, Inc.
  2. This file is part of the GNU C Library.
  3. Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
  4. The GNU C Library is free software; you can redistribute it and/or
  5. modify it under the terms of the GNU Lesser General Public
  6. License as published by the Free Software Foundation; either
  7. version 2.1 of the License, or (at your option) any later version.
  8. The GNU C Library is distributed in the hope that it will be useful,
  9. but WITHOUT ANY WARRANTY; without even the implied warranty of
  10. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  11. Lesser General Public License for more details.
  12. You should have received a copy of the GNU Lesser General Public
  13. License along with the GNU C Library; if not, write to the Free
  14. Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  15. 02111-1307 USA. */
  16. #include <errno.h>
  17. #include <signal.h>
  18. #include "pthreadP.h"
  19. #include "atomic.h"
  20. #include <sysdep.h>
  21. #include <bits/kernel-features.h>
  22. int
  23. pthread_cancel (
  24. pthread_t th)
  25. {
  26. volatile struct pthread *pd = (volatile struct pthread *) th;
  27. /* Make sure the descriptor is valid. */
  28. if (INVALID_TD_P (pd))
  29. /* Not a valid thread handle. */
  30. return ESRCH;
  31. #ifdef SHARED
  32. pthread_cancel_init ();
  33. #endif
  34. int result = 0;
  35. int oldval;
  36. int newval;
  37. do
  38. {
  39. again:
  40. oldval = pd->cancelhandling;
  41. newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
  42. /* Avoid doing unnecessary work. The atomic operation can
  43. potentially be expensive if the bug has to be locked and
  44. remote cache lines have to be invalidated. */
  45. if (oldval == newval)
  46. break;
  47. /* If the cancellation is handled asynchronously just send a
  48. signal. We avoid this if possible since it's more
  49. expensive. */
  50. if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
  51. {
  52. /* Mark the cancellation as "in progress". */
  53. if (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling,
  54. oldval | CANCELING_BITMASK,
  55. oldval))
  56. goto again;
  57. /* The cancellation handler will take care of marking the
  58. thread as canceled. */
  59. INTERNAL_SYSCALL_DECL (err);
  60. /* One comment: The PID field in the TCB can temporarily be
  61. changed (in fork). But this must not affect this code
  62. here. Since this function would have to be called while
  63. the thread is executing fork, it would have to happen in
  64. a signal handler. But this is no allowed, pthread_cancel
  65. is not guaranteed to be async-safe. */
  66. int val;
  67. #if __ASSUME_TGKILL
  68. val = INTERNAL_SYSCALL (tgkill, err, 3,
  69. THREAD_GETMEM (THREAD_SELF, pid), pd->tid,
  70. SIGCANCEL);
  71. #else
  72. # ifdef __NR_tgkill
  73. val = INTERNAL_SYSCALL (tgkill, err, 3,
  74. THREAD_GETMEM (THREAD_SELF, pid), pd->tid,
  75. SIGCANCEL);
  76. if (INTERNAL_SYSCALL_ERROR_P (val, err)
  77. && INTERNAL_SYSCALL_ERRNO (val, err) == ENOSYS)
  78. # endif
  79. val = INTERNAL_SYSCALL (tkill, err, 2, pd->tid, SIGCANCEL);
  80. #endif
  81. if (INTERNAL_SYSCALL_ERROR_P (val, err))
  82. result = INTERNAL_SYSCALL_ERRNO (val, err);
  83. break;
  84. }
  85. }
  86. /* Mark the thread as canceled. This has to be done
  87. atomically since other bits could be modified as well. */
  88. while (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling, newval,
  89. oldval));
  90. return result;
  91. }
  92. PTHREAD_STATIC_FN_REQUIRE (pthread_create)