/************************************************************
 * task_delete.c
 *
 *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
 *
 * 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  <nuttx/os_external.h>
#include  "os_internal.h"
#ifndef CONFIG_DISABLE_SIGNALS
# include "sig_internal.h"
#endif

/************************************************************
 * Definitions
 ************************************************************/

/************************************************************
 * Private Type Declarations
 ************************************************************/

/************************************************************
 * Global Variables
 ************************************************************/

/************************************************************
 * Private Variables
 ************************************************************/

/************************************************************
 * Private Function Prototypes
 ************************************************************/

/************************************************************
 * Private Functions
 ************************************************************/

/************************************************************
 * Public Functions
 ************************************************************/

/************************************************************
 * Name: task_delete
 *
 * Description:
 *   This function causes a specified task to cease to exist.
 *   Its  stack and TCB will be deallocated.  This function
 *   is the companion to task_create().
 *
 * Inputs:
 *   pid - The task ID of the task to delete.  A pid of zero
 *         signifies the calling task.
 *
 * Return Value:
 *   OK on success; or ERROR on failure
 *
 *   This function can fail if the provided pid does not
 *   correspond to a task (errno is not set)
 *
 ************************************************************/

STATUS task_delete(pid_t pid)
{
  FAR _TCB  *rtcb;
  FAR _TCB  *dtcb;
  irqstate_t saved_state;
  STATUS     ret = ERROR;

   /* Check if the task to delete is the calling task */

   rtcb = (FAR _TCB*)g_readytorun.head;
   if (pid == 0 || pid == rtcb->pid)
     {
       /* If it is, then what we really wanted to do was exit.
        * Note that we don't bother to unlock the TCB since
        * it will be going away.
        */

       exit(EXIT_SUCCESS);
     }

  /* Make sure the task does not become ready-to-run while
   * we are futzing with its TCB by locking ourselves as the
   * executing task.
   *
   * Frist, find for the TCB associated with matching pid 
   */

   dtcb = sched_gettcb(pid);
   if (!dtcb)
     {
        /* This pid does not correspond to any known task */

        sched_unlock();
        return ERROR;
     }

  /* Verify our internal sanity */

  if (dtcb->task_state == TSTATE_TASK_RUNNING ||
      dtcb->task_state >= NUM_TASK_STATES)
    {
      sched_unlock();
      PANIC(OSERR_BADDELETESTATE);
    }

  saved_state = irqsave();

  /* Inform the instrumentation layer that the task has stopped */

  sched_note_stop(dtcb);

  /* Remove the task from the OS's tasks lists. */

  dq_rem((FAR dq_entry_t*)dtcb, g_tasklisttable[dtcb->task_state].list);
  dtcb->task_state = TSTATE_TASK_INVALID;
  irqrestore(saved_state);

  /* At this point, the TCB should no longer be accessible to the system */

  sched_unlock();

  /* Deallocate anything left in the TCB's queues */

#ifndef CONFIG_DISABLE_SIGNALS
  sig_cleanup(dtcb); /* Deallocate Signal lists */
#endif

  /* Deallocate its TCB */

  sched_releasetcb(dtcb);
  return ret;
}