pthread_cancel.c 3.0 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, see
  14. <http://www.gnu.org/licenses/>. */
  15. #include <errno.h>
  16. #include <signal.h>
  17. #include "pthreadP.h"
  18. #include "atomic.h"
  19. #include <sysdep.h>
  20. #include <bits/kernel-features.h>
  21. int
  22. pthread_cancel (
  23. pthread_t th)
  24. {
  25. volatile struct pthread *pd = (volatile struct pthread *) th;
  26. /* Make sure the descriptor is valid. */
  27. if (INVALID_TD_P (pd))
  28. /* Not a valid thread handle. */
  29. return ESRCH;
  30. #ifdef SHARED
  31. pthread_cancel_init ();
  32. #endif
  33. int result = 0;
  34. int oldval;
  35. int newval;
  36. do
  37. {
  38. again:
  39. oldval = pd->cancelhandling;
  40. newval = oldval | CANCELING_BITMASK | CANCELED_BITMASK;
  41. /* Avoid doing unnecessary work. The atomic operation can
  42. potentially be expensive if the bug has to be locked and
  43. remote cache lines have to be invalidated. */
  44. if (oldval == newval)
  45. break;
  46. /* If the cancellation is handled asynchronously just send a
  47. signal. We avoid this if possible since it's more
  48. expensive. */
  49. if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
  50. {
  51. /* Mark the cancellation as "in progress". */
  52. if (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling,
  53. oldval | CANCELING_BITMASK,
  54. oldval))
  55. goto again;
  56. /* The cancellation handler will take care of marking the
  57. thread as canceled. */
  58. INTERNAL_SYSCALL_DECL (err);
  59. /* One comment: The PID field in the TCB can temporarily be
  60. changed (in fork). But this must not affect this code
  61. here. Since this function would have to be called while
  62. the thread is executing fork, it would have to happen in
  63. a signal handler. But this is no allowed, pthread_cancel
  64. is not guaranteed to be async-safe. */
  65. int val;
  66. val = INTERNAL_SYSCALL (tgkill, err, 3,
  67. THREAD_GETMEM (THREAD_SELF, pid), pd->tid,
  68. SIGCANCEL);
  69. if (INTERNAL_SYSCALL_ERROR_P (val, err))
  70. result = INTERNAL_SYSCALL_ERRNO (val, err);
  71. break;
  72. }
  73. }
  74. /* Mark the thread as canceled. This has to be done
  75. atomically since other bits could be modified as well. */
  76. while (atomic_compare_and_exchange_bool_acq (&pd->cancelhandling, newval,
  77. oldval));
  78. return result;
  79. }
  80. PTHREAD_STATIC_FN_REQUIRE (pthread_create)