text: /****************************************************************************
   *  arch/avr/src/avr/up_unblocktask.c
   *
   *   Copyright (C) 2011, 2013, 2015 Gregory Nutt. All rights reserved.
   *   Author: Gregory Nutt <gnutt@nuttx.org>
   *
   * 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 NuttX 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 <sched.h>
  #include <debug.h>
  #include <nuttx/arch.h>
  #include <nuttx/sched.h>
  
  #include "sched/sched.h"
  #include "clock/clock.h"
  #include "up_internal.h"
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: up_unblock_task
   *
   * Description:
   *   A task is currently in an inactive task list
   *   but has been prepped to execute.  Move the TCB to the
   *   ready-to-run list, restore its context, and start execution.
   *
   * Input Parameters:
   *   tcb: Refers to the tcb to be unblocked.  This tcb is
   *     in one of the waiting tasks lists.  It must be moved to
   *     the ready-to-run list and, if it is the highest priority
   *     ready to run taks, executed.
   *
   ****************************************************************************/
  
  void up_unblock_task(struct tcb_s *tcb)
  {
    struct tcb_s *rtcb = this_task();
  
    /* Verify that the context switch can be performed */
  
    DEBUGASSERT((tcb->task_state >= FIRST_BLOCKED_STATE) &&
           (tcb->task_state <= LAST_BLOCKED_STATE));
  
    /* Remove the task from the blocked task list */
  
    sched_removeblocked(tcb);
  
    /* Add the task in the correct location in the prioritized
     * ready-to-run task list
     */
  
    if (sched_addreadytorun(tcb))
      {
        /* The currently active task has changed! We need to do
         * a context switch to the new task.
         */
  
        /* Update scheduler parameters */
  
        sched_suspend_scheduler(rtcb);
  
        /* Are we in an interrupt handler? */
  
        if (g_current_regs)
          {
            /* Yes, then we have to do things differently.
             * Just copy the g_current_regs into the OLD rtcb.
             */
  
            up_savestate(rtcb->xcp.regs);
  
            /* Restore the exception context of the rtcb at the (new) head
             * of the ready-to-run task list.
             */
  
            rtcb = this_task();
  
            /* Update scheduler parameters */
  
            sched_resume_scheduler(rtcb);
  
            /* Then switch contexts */
  
            up_restorestate(rtcb->xcp.regs);
          }
  
        /* No, then we will need to perform the user context switch */
  
        else
          {
            struct tcb_s *nexttcb = this_task();
  
            /* Update scheduler parameters */
  
            sched_resume_scheduler(nexttcb);
  
            /* Switch context to the context of the task at the head of the
             * ready to run list.
             */
  
            up_switchcontext(rtcb->xcp.regs, nexttcb->xcp.regs);
  
            /* up_switchcontext forces a context switch to the task at the
             * head of the ready-to-run list.  It does not 'return' in the
             * normal sense.  When it does return, it is because the blocked
             * task is again ready to run and has execution priority.
             */
          }
      }
  }
  
  