up_releasepending.c

這是一個實時嵌入式作業系統 實作了MCS51 ARM等MCU

/************************************************************
 * common/up_releasepending.c
 *
 *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <[e-mail]>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name Gregory Nutt 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
 * COPYRIGHT OWNER 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.
 *
 ************************************************************/

/************************************************************
 * Included Files
 ************************************************************/

#include <nuttx/config.h>
#include <sys/types.h>
#include <sched.h>
#include <debug.h>
#include <nuttx/arch.h>
#include "os_internal.h"
#include "up_internal.h"

/************************************************************
 * Private Definitions
 ************************************************************/

/************************************************************
 * Private Data
 ************************************************************/

/************************************************************
 * Private Funtions
 ************************************************************/

/************************************************************
 * Public Funtions
 ************************************************************/

/************************************************************
 * Name: up_release_pending
 *
 * Description:
 *   Release and ready-to-run tasks that have
 *   collected in the pending task list.  This can call a
 *   context switch if a new task is placed at the head of
 *   the ready to run list.
 *
 ************************************************************/

void up_release_pending(void)
{
  _TCB *rtcb = (_TCB*)g_readytorun.head;

  lldbg("From TCB=%p\n", rtcb);

  /* Merge the g_pendingtasks list into the g_readytorun task list */

  /* sched_lock(); */
  if (sched_mergepending())
    {
      /* The currently active task has changed!  We will need to
       * switch contexts.  First check if we are operating in
       * interrupt context:
       */

      if (current_regs)
        {
          /* Yes, then we have to do things differently.
           * Just copy the current_regs into the OLD rtcb.
           */

           up_copystate(rtcb->xcp.regs, current_regs);

          /* Restore the exception context of the rtcb at the (new) head 
           * of the g_readytorun task list.
           */

          rtcb = (_TCB*)g_readytorun.head;
          lldbg("New Active Task TCB=%p\n", rtcb);

          /* Then switch contexts */

          up_copystate(current_regs, rtcb->xcp.regs);
        }

      /* Copy the exception context into the TCB of the task that
       * was currently active. if up_saveusercontext returns a non-zero
       * value, then this is really the previously running task 
       * restarting!
       */

      else if (!up_saveusercontext(rtcb->xcp.regs))
        {
          /* Restore the exception context of the rtcb at the (new) head 
           * of the g_readytorun task list.
           */

          rtcb = (_TCB*)g_readytorun.head;
          lldbg("New Active Task TCB=%p\n", rtcb);

           /* Then switch contexts */

          up_fullcontextrestore(rtcb->xcp.regs);
        }
    }
}