semaphore.c

MANTIS是由科罗拉多大学开发的传感器网络嵌入式操作系统。 这是mantis的0.9.5版本的源码。

//  This file is part of MANTIS OS, Operating System
//  See http://mantis.cs.colorado.edu/
//
//  Copyright (C) 2003,2004,2005 University of Colorado, Boulder
//
//  This program is free software; you can redistribute it and/or
//  modify it under the terms of the mos license (see file LICENSE)

/*
  Project Mantis
  File: semaphore.c
  Author: Jeff Rose
  Edited by Hui Dai
  Date: 1-30-03

  Standard counting semaphores...
*/

/** @file semaphore.c
 * @brief Standard counting semaphores.
 * @author Jeff Rose
 * @author Edited by Hui Dai
 * @date Created: 01/30/2003
 */

#include "mos.h"

#include "sem.h"
#include "tlist.h"

void mos_sem_init(mos_sem_t *s, int value)
{
   s->val = value;
   mos_tlist_init(&s->q);
}

void mos_sem_select_post(mos_sem_t *s, uint16_t thread)
{
   handle_t int_handle;
   thread_t *selected;
   int_handle = mos_disable_ints();

   // Post a unit and wake-up the next waiting thread
   s->val++;
   
   if((selected = mos_tlist_get_thread(&s->q, thread)) != NULL) {
      //mos_thread_resume_noints_nodispatch(selected, int_handle);
      //mos_enable_ints(int_handle);
      mos_thread_resume_noints(selected, int_handle);
   } else {
      mos_enable_ints(int_handle);
   }
}

void mos_sem_post(mos_sem_t *s)
{
   handle_t int_handle;
   thread_t *thread;
   int_handle = mos_disable_ints();

   // Post a unit and wake-up the next waiting thread
   s->val++;
   
   if((thread = mos_tlist_remove(&s->q)) != NULL) {
      //mos_thread_resume_noints_nodispatch(thread, int_handle);
      //mos_enable_ints(int_handle);
      mos_thread_resume_noints(thread, int_handle);
   } else {
      mos_enable_ints(int_handle);
   }
}

void mos_sem_wait(mos_sem_t *s)
{
   handle_t int_handle;
   int_handle = mos_disable_ints();

   s->val--;

   // If no resources are available then we wait in the queue
   if(s->val < 0) {
      thread_t *id;
      id = mos_thread_current();
      mos_tlist_add(&s->q, id);
      mos_thread_suspend_noints(int_handle);
   } else
      mos_enable_ints(int_handle);
}


uint8_t mos_sem_try_wait(mos_sem_t *s)
{
   handle_t int_handle;
   int_handle = mos_disable_ints();

   if(s->val > 0) {
      s->val--;
      mos_enable_ints(int_handle);
      return SEM_SUCCESS;
   } else {
      mos_enable_ints(int_handle);
      return SEM_FAIL;
   }
}