diff options
Diffstat (limited to 'sysdeps/generic/sem-post.c')
-rw-r--r-- | sysdeps/generic/sem-post.c | 62 |
1 files changed, 62 insertions, 0 deletions
diff --git a/sysdeps/generic/sem-post.c b/sysdeps/generic/sem-post.c new file mode 100644 index 00000000..c283784e --- /dev/null +++ b/sysdeps/generic/sem-post.c @@ -0,0 +1,62 @@ +/* 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 <semaphore.h> +#include <assert.h> + +#include <pt-internal.h> + +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); |