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