ea6658a2ab
git-svn-id: http://svn.lfbs.rwth-aachen.de/svn/scc/trunk/MetalSVM@52 315a16e6-25f9-4109-90ae-ca3045a26c18
132 lines
2.5 KiB
C
132 lines
2.5 KiB
C
/*
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* Copyright 2010 Stefan Lankes, Chair for Operating Systems,
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* RWTH Aachen University
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* This file is part of MetalSVM.
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*/
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#ifndef __SEMAPHORE_H__
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#define __SEMAPHORE_H__
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#include <metalsvm/string.h>
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#include <metalsvm/tasks.h>
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#include <metalsvm/spinlock.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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typedef struct {
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unsigned int value;
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tid_t queue[MAX_TASKS];
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unsigned int pos;
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spinlock_t lock;
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} sem_t;
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#define SEM_INIT(v) {v, {[0 ... MAX_TASKS-1] = MAX_TASKS}, 0, SPINLOCK_INIT};
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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 -1;
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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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inline static int sem_destroy(sem_t* s) {
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if (BUILTIN_EXPECT(!s, 0))
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return -1;
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spinlock_destroy(&s->lock);
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return 0;
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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 -1;
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next_try:
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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_task(current_task->id);
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spinlock_unlock(&s->lock);
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reschedule();
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goto next_try;
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}
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return 0;
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}
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inline static int sem_trywait(sem_t* s) {
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int ret = -1;
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if (BUILTIN_EXPECT(!s, 0))
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return -1;
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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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inline static int sem_post(sem_t* s) {
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if (BUILTIN_EXPECT(!s, 0))
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return -1;
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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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