sem_post.c 1.4 KB

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  1. /* sem_post -- post to a POSIX semaphore. Powerpc version.
  2. Copyright (C) 2003, 2004, 2007 Free Software Foundation, Inc.
  3. This file is part of the GNU C Library.
  4. Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003.
  5. The GNU C Library is free software; you can redistribute it and/or
  6. modify it under the terms of the GNU Lesser General Public
  7. License as published by the Free Software Foundation; either
  8. version 2.1 of the License, or (at your option) any later version.
  9. The GNU C Library is distributed in the hope that it will be useful,
  10. but WITHOUT ANY WARRANTY; without even the implied warranty of
  11. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  12. Lesser General Public License for more details.
  13. You should have received a copy of the GNU Lesser General Public
  14. License along with the GNU C Library; if not, see
  15. <http://www.gnu.org/licenses/>. */
  16. #include <errno.h>
  17. #include <sysdep.h>
  18. #include <lowlevellock.h>
  19. #include <internaltypes.h>
  20. #include <semaphore.h>
  21. int
  22. sem_post (sem_t *sem)
  23. {
  24. struct new_sem *isem = (struct new_sem *) sem;
  25. __asm__ __volatile__ (__lll_rel_instr ::: "memory");
  26. atomic_increment (&isem->value);
  27. __asm__ __volatile__ (__lll_acq_instr ::: "memory");
  28. if (isem->nwaiters > 0)
  29. {
  30. int err = lll_futex_wake (&isem->value, 1,
  31. isem->private ^ FUTEX_PRIVATE_FLAG);
  32. if (__builtin_expect (err, 0) < 0)
  33. {
  34. __set_errno (-err);
  35. return -1;
  36. }
  37. }
  38. return 0;
  39. }