/* Post a semaphore. Generic version. Copyright (C) 2005 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License for more details. You should have received a copy of the GNU Library General Public License along with the GNU C Library; see the file COPYING.LIB. If not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #include #include #include int __sem_post (sem_t *sem) { struct __pthread *wakeup; __pthread_spin_lock (&sem->__lock); if (sem->__value > 0) /* Do a quick up. */ { assert (! sem->__queue); sem->__value ++; __pthread_spin_unlock (&sem->__lock); return 0; } if (! sem->__queue) /* No one waiting. */ { sem->__value = 1; __pthread_spin_unlock (&sem->__lock); return 0; } /* Wake someone up. */ /* First dequeue someone. */ wakeup = sem->__queue; __pthread_dequeue (wakeup); /* Then drop the lock and transfer control. */ __pthread_spin_unlock (&sem->__lock); __pthread_wakeup (wakeup); return 0; } weak_alias (__sem_post, sem_post);