pthread_rwlock_tryrdlock.c 1.5 KB

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  1. /* Copyright (C) 2002, 2007 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 "pthreadP.h"
  17. #include <lowlevellock.h>
  18. int
  19. __pthread_rwlock_tryrdlock (
  20. pthread_rwlock_t *rwlock)
  21. {
  22. int result = EBUSY;
  23. lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
  24. if (rwlock->__data.__writer == 0
  25. && (rwlock->__data.__nr_writers_queued == 0
  26. || PTHREAD_RWLOCK_PREFER_READER_P (rwlock)))
  27. {
  28. if (__builtin_expect (++rwlock->__data.__nr_readers == 0, 0))
  29. {
  30. --rwlock->__data.__nr_readers;
  31. result = EAGAIN;
  32. }
  33. else
  34. result = 0;
  35. }
  36. lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
  37. return result;
  38. }
  39. strong_alias (__pthread_rwlock_tryrdlock, pthread_rwlock_tryrdlock)