mirror of
https://gitlab.com/sortix/sortix.git
synced 2023-02-13 20:55:38 -05:00
38 lines
1.4 KiB
C++
38 lines
1.4 KiB
C++
/*******************************************************************************
|
|
|
|
Copyright(C) Jonas 'Sortie' Termansen 2014.
|
|
|
|
This file is part of Sortix libpthread.
|
|
|
|
Sortix libpthread is free software: you can redistribute it and/or modify it
|
|
under the terms of the GNU Lesser General Public License as published by the
|
|
Free Software Foundation, either version 3 of the License, or (at your
|
|
option) any later version.
|
|
|
|
Sortix libpthread 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 Lesser General Public
|
|
License for more details.
|
|
|
|
You should have received a copy of the GNU Lesser General Public License
|
|
along with Sortix libpthread. If not, see <http://www.gnu.org/licenses/>.
|
|
|
|
sem_trywait.c++
|
|
Lock a semaphore.
|
|
|
|
*******************************************************************************/
|
|
|
|
#include <errno.h>
|
|
#include <semaphore.h>
|
|
|
|
extern "C" int sem_trywait(sem_t* sem)
|
|
{
|
|
int old_value = __atomic_load_n(&sem->value, __ATOMIC_SEQ_CST);
|
|
if ( old_value <= 0 )
|
|
return errno = EAGAIN, -1;
|
|
int new_value = old_value - 1;
|
|
if ( !__atomic_compare_exchange_n(&sem->value, &old_value, new_value, false,
|
|
__ATOMIC_SEQ_CST, __ATOMIC_RELAXED) )
|
|
return errno = EAGAIN, -1;
|
|
return 0;
|
|
}
|