add semaphore, which does not base busy-waiting
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Stefan Lankes
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2 changed files with 238 additions and 0 deletions
176
include/eduos/semaphore.h
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176
include/eduos/semaphore.h
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/*
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* Copyright (c) 2010, Stefan Lankes, RWTH Aachen University
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this
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* software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/**
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* @author Stefan Lankes
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* @file include/eduos/semaphore.h
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* @brief semaphore functions definition
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*/
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#ifndef __SEMAPHORE_H__
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#define __SEMAPHORE_H__
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#include <eduos/string.h>
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#include <eduos/semaphore_types.h>
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#include <eduos/spinlock.h>
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#include <eduos/errno.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/** @brief Semaphore initialization
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*
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* Always init semaphores before use!
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*
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* @param s Pointer to semaphore structure to initialize
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* @param v Resource count
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*
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* @return
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* - 0 on success
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* - -EINVAL on invalid argument
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*/
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inline static int sem_init(sem_t* s, unsigned int v) {
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unsigned int i;
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if (BUILTIN_EXPECT(!s, 0))
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return -EINVAL;
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s->value = v;
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s->pos = 0;
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for(i=0; i<MAX_TASKS; i++)
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s->queue[i] = MAX_TASKS;
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spinlock_init(&s->lock);
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return 0;
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}
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/** @brief Destroy semaphore
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* @return
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* - 0 on success
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* - -EINVAL on invalid argument
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*/
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inline static int sem_destroy(sem_t* s) {
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if (BUILTIN_EXPECT(!s, 0))
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return -EINVAL;
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spinlock_destroy(&s->lock);
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return 0;
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}
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/** @brief Nonblocking trywait for sempahore
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*
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* Will return immediately if not available
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*
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* @return
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* - 0 on success (You got the semaphore)
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* - -EINVAL on invalid argument
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* - -ECANCELED on failure (You still have to wait)
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*/
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inline static int sem_trywait(sem_t* s) {
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int ret = -ECANCELED;
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if (BUILTIN_EXPECT(!s, 0))
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return -EINVAL;
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spinlock_lock(&s->lock);
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if (s->value > 0) {
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s->value--;
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ret = 0;
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}
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spinlock_unlock(&s->lock);
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return ret;
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}
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/** @brief Blocking wait for semaphore
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*
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* @param s Address of the according sem_t structure
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* @return
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* - 0 on success
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* - -EINVAL on invalid argument
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* - -ETIME on timer expired
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*/
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inline static int sem_wait(sem_t* s) {
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if (BUILTIN_EXPECT(!s, 0))
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return -EINVAL;
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next_try1:
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spinlock_lock(&s->lock);
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if (s->value > 0) {
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s->value--;
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spinlock_unlock(&s->lock);
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} else {
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s->queue[s->pos] = current_task->id;
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s->pos = (s->pos + 1) % MAX_TASKS;
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block_current_task();
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spinlock_unlock(&s->lock);
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reschedule();
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goto next_try1;
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}
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return 0;
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}
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/** @brief Give back resource
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* @return
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* - 0 on success
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* - -EINVAL on invalid argument
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*/
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inline static int sem_post(sem_t* s) {
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if (BUILTIN_EXPECT(!s, 0))
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return -EINVAL;
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spinlock_lock(&s->lock);
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if (s->value > 0) {
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s->value++;
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spinlock_unlock(&s->lock);
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} else {
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unsigned int k, i;
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s->value++;
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i = s->pos;
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for(k=0; k<MAX_TASKS; k++) {
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if (s->queue[i] < MAX_TASKS) {
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wakeup_task(s->queue[i]);
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s->queue[i] = MAX_TASKS;
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break;
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}
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i = (i + 1) % MAX_TASKS;
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}
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spinlock_unlock(&s->lock);
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}
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return 0;
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}
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#ifdef __cplusplus
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}
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#endif
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#endif
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62
include/eduos/semaphore_types.h
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62
include/eduos/semaphore_types.h
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@ -0,0 +1,62 @@
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/*
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* Copyright (c) 2010, Stefan Lankes, RWTH Aachen University
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this
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* software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/**
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* @author Stefan Lankes
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* @file include/eduos/semaphore_types.h
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* @brief semaphore type definition
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*/
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#ifndef __SEMAPHORE_TYPES_H__
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#define __SEMAPHORE_TYPES_H__
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#include <eduos/spinlock_types.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/** @brief Semaphore structure */
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typedef struct {
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/// Resource available count
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unsigned int value;
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/// Queue of waiting tasks
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tid_t queue[MAX_TASKS];
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/// Position in queue
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unsigned int pos;
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/// Access lock
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spinlock_t lock;
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} sem_t;
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/// Macro for initialization of semaphore
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#define SEM_INIT(v) {v, {[0 ... MAX_TASKS-1] = MAX_TASKS}, 0, SPINLOCK_INIT}
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#ifdef __cplusplus
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}
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#endif
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#endif
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