add semaphore, which does not base busy-waiting

This commit is contained in:
Stefan Lankes 2013-11-26 09:17:59 +01:00
parent ba491114bc
commit de9207a6b2
2 changed files with 238 additions and 0 deletions

176
include/eduos/semaphore.h Normal file
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/*
* Copyright (c) 2010, Stefan Lankes, RWTH Aachen University
* 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.
* * Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 REGENTS OR CONTRIBUTORS 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.
*/
/**
* @author Stefan Lankes
* @file include/eduos/semaphore.h
* @brief semaphore functions definition
*/
#ifndef __SEMAPHORE_H__
#define __SEMAPHORE_H__
#include <eduos/string.h>
#include <eduos/semaphore_types.h>
#include <eduos/spinlock.h>
#include <eduos/errno.h>
#ifdef __cplusplus
extern "C" {
#endif
/** @brief Semaphore initialization
*
* Always init semaphores before use!
*
* @param s Pointer to semaphore structure to initialize
* @param v Resource count
*
* @return
* - 0 on success
* - -EINVAL on invalid argument
*/
inline static int sem_init(sem_t* s, unsigned int v) {
unsigned int i;
if (BUILTIN_EXPECT(!s, 0))
return -EINVAL;
s->value = v;
s->pos = 0;
for(i=0; i<MAX_TASKS; i++)
s->queue[i] = MAX_TASKS;
spinlock_init(&s->lock);
return 0;
}
/** @brief Destroy semaphore
* @return
* - 0 on success
* - -EINVAL on invalid argument
*/
inline static int sem_destroy(sem_t* s) {
if (BUILTIN_EXPECT(!s, 0))
return -EINVAL;
spinlock_destroy(&s->lock);
return 0;
}
/** @brief Nonblocking trywait for sempahore
*
* Will return immediately if not available
*
* @return
* - 0 on success (You got the semaphore)
* - -EINVAL on invalid argument
* - -ECANCELED on failure (You still have to wait)
*/
inline static int sem_trywait(sem_t* s) {
int ret = -ECANCELED;
if (BUILTIN_EXPECT(!s, 0))
return -EINVAL;
spinlock_lock(&s->lock);
if (s->value > 0) {
s->value--;
ret = 0;
}
spinlock_unlock(&s->lock);
return ret;
}
/** @brief Blocking wait for semaphore
*
* @param s Address of the according sem_t structure
* @return
* - 0 on success
* - -EINVAL on invalid argument
* - -ETIME on timer expired
*/
inline static int sem_wait(sem_t* s) {
if (BUILTIN_EXPECT(!s, 0))
return -EINVAL;
next_try1:
spinlock_lock(&s->lock);
if (s->value > 0) {
s->value--;
spinlock_unlock(&s->lock);
} else {
s->queue[s->pos] = current_task->id;
s->pos = (s->pos + 1) % MAX_TASKS;
block_current_task();
spinlock_unlock(&s->lock);
reschedule();
goto next_try1;
}
return 0;
}
/** @brief Give back resource
* @return
* - 0 on success
* - -EINVAL on invalid argument
*/
inline static int sem_post(sem_t* s) {
if (BUILTIN_EXPECT(!s, 0))
return -EINVAL;
spinlock_lock(&s->lock);
if (s->value > 0) {
s->value++;
spinlock_unlock(&s->lock);
} else {
unsigned int k, i;
s->value++;
i = s->pos;
for(k=0; k<MAX_TASKS; k++) {
if (s->queue[i] < MAX_TASKS) {
wakeup_task(s->queue[i]);
s->queue[i] = MAX_TASKS;
break;
}
i = (i + 1) % MAX_TASKS;
}
spinlock_unlock(&s->lock);
}
return 0;
}
#ifdef __cplusplus
}
#endif
#endif

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/*
* Copyright (c) 2010, Stefan Lankes, RWTH Aachen University
* 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.
* * Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this
* software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 REGENTS OR CONTRIBUTORS 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.
*/
/**
* @author Stefan Lankes
* @file include/eduos/semaphore_types.h
* @brief semaphore type definition
*/
#ifndef __SEMAPHORE_TYPES_H__
#define __SEMAPHORE_TYPES_H__
#include <eduos/spinlock_types.h>
#ifdef __cplusplus
extern "C" {
#endif
/** @brief Semaphore structure */
typedef struct {
/// Resource available count
unsigned int value;
/// Queue of waiting tasks
tid_t queue[MAX_TASKS];
/// Position in queue
unsigned int pos;
/// Access lock
spinlock_t lock;
} sem_t;
/// Macro for initialization of semaphore
#define SEM_INIT(v) {v, {[0 ... MAX_TASKS-1] = MAX_TASKS}, 0, SPINLOCK_INIT}
#ifdef __cplusplus
}
#endif
#endif