/* * Copyright (c) 2001-2004 Jakub Jermar * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * - Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * - Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * - The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ /** @addtogroup kernel_sync * @{ */ /** * @file * @brief Semaphores. */ #include <synch/semaphore.h> #include <synch/waitq.h> #include <synch/spinlock.h> #include <arch/asm.h> #include <arch.h> /** Initialize semaphore * * Initialize semaphore. * * @param sem Semaphore. * @param val Maximal number of threads allowed to enter critical section. * */ void semaphore_initialize(semaphore_t *sem, int val) { waitq_initialize_with_count(&sem->wq, val); } errno_t semaphore_trydown(semaphore_t *sem) { return semaphore_down_timeout(sem, 0); } /** Semaphore down with timeout * * @param sem Semaphore. * @param usec Timeout in microseconds. * * @return See comment for waitq_sleep_timeout(). * */ errno_t semaphore_down_timeout(semaphore_t *sem, uint32_t usec) { errno_t rc = waitq_sleep_timeout(&sem->wq, usec); assert(rc == EOK || rc == ETIMEOUT || rc == EAGAIN); return rc; } void semaphore_down(semaphore_t *sem) { errno_t rc = waitq_sleep(&sem->wq); assert(rc == EOK); } /** Semaphore up * * Semaphore up. * * @param s Semaphore. * */ void semaphore_up(semaphore_t *sem) { waitq_wake_one(&sem->wq); } /** @} */