text: /****************************************************************************
   * up_unblocktask.c
   *
   *   Copyright (C) 2007-2009, 2013 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 "clock_internal.h"
  #include "os_internal.h"
  #include "up_internal.h"
  
  /****************************************************************************
   * Private Definitions
   ****************************************************************************/
  
  /****************************************************************************
   * Private Data
   ****************************************************************************/
  
  /****************************************************************************
   * Private Functions
   ****************************************************************************/
  
  /****************************************************************************
   * 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.
   *
   * Inputs:
   *   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 = (struct tcb_s*)g_readytorun.head;
  
    /* Verify that the context switch can be performed */
  
    ASSERT((tcb->task_state >= FIRST_BLOCKED_STATE) &&
           (tcb->task_state <= LAST_BLOCKED_STATE));
  
    sdbg("Unblocking TCB=%p\n", tcb);
  
    /* Remove the task from the blocked task list */
  
    sched_removeblocked(tcb);
  
    /* Reset its timeslice.  This is only meaningful for round
     * robin tasks but it doesn't here to do it for everything
     */
  
  #if CONFIG_RR_INTERVAL > 0
    tcb->timeslice = CONFIG_RR_INTERVAL / MSEC_PER_TICK;
  #endif
  
    /* Add the task in the correct location in the prioritized
     * g_readytorun task list
     */
  
    if (sched_addreadytorun(tcb))
      {
        /* The currently active task has changed! Copy the exception context
         * into the TCB of the task that was previously active.  if 
         * up_setjmp returns a non-zero value, then this is really the
         * previously running task restarting!
         */
  
        if (!up_setjmp(rtcb->xcp.regs))
          {
            /* Restore the exception context of the new task that is ready to
             * run (probably tcb).  This is the new rtcb at the head of the
             * g_readytorun task list.
             */
  
            rtcb = (struct tcb_s*)g_readytorun.head;
            sdbg("New Active Task TCB=%p\n", rtcb);
  
            /* The way that we handle signals in the simulation is kind of
             * a kludge.  This would be unsafe in a truly multi-threaded, interrupt
             * driven environment.
             */
  
            if (rtcb->xcp.sigdeliver)
              {
                sdbg("Delivering signals TCB=%p\n", rtcb);
                ((sig_deliver_t)rtcb->xcp.sigdeliver)(rtcb);
                rtcb->xcp.sigdeliver = NULL;
              }
  
            /* Then switch contexts */
  
            up_longjmp(rtcb->xcp.regs, 1);
         }
      }
  }
  