nuttx/sched/sched_removereadytorun.c

/****************************************************************************
 * shced/sched_removereadytorun.c
 *
 *   Copyright (C) 2007-2009, 2012 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:
 *
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 *    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
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 *    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
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 ****************************************************************************/

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

#include <nuttx/config.h>

#include <stdbool.h>
#include <queue.h>
#include <assert.h>

#include "os_internal.h"

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

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

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

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

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

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

/****************************************************************************
 * Name: sched_removereadytorun
 *
 * Description:
 *   This function removes a TCB from the ready to run list.
 *
 * Inputs:
 *   rtcb - Points to the TCB that is ready-to-run
 *
 * Return Value:
 *   true if the currently active task (the head of the 
 *     g_readytorun list) has changed.
 *
 * Assumptions:
 * - The caller has established a critical section before calling this
 *   function (calling sched_lock() first is NOT a good idea -- use irqsave()).
 * - The caller handles the condition that occurs if the
 *   the head of the g_readytorun list is changed.
 *
 ****************************************************************************/

bool sched_removereadytorun(FAR _TCB *rtcb)
{
  bool ret = false;

  /* Check if the TCB to be removed is at the head of the ready to run list.
   * In this case, we are removing the currently active task.
   */

  if (!rtcb->blink)
    {
      /* There must always be at least one task in the list (the idle task) */

      ASSERT(rtcb->flink != NULL);

      /* Inform the instrumentation layer that we are switching tasks */

      sched_note_switch(rtcb, rtcb->flink);

      rtcb->flink->task_state = TSTATE_TASK_RUNNING;
      ret = true;
    }

  /* Remove the TCB from the ready-to-run list */

  dq_rem((FAR dq_entry_t*)rtcb, (dq_queue_t*)&g_readytorun);

  rtcb->task_state = TSTATE_TASK_INVALID;
  return ret;
}