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  /* Allocate a TCB for the new taskernelkernel thread.  kmm_zalloc() is
   * used to that all fields of the new TCB will be zeroed.
   */

  tcb = (FAR struct task_tcb_s *)kmm_zalloc(sizeof(struct task_tcb_s));
  if (tcb == NULL)
    {
      return -ENOMEM;
    }

  /* Indicate (1) that this is a kernel thread and that (2) a custom
   * stack will be used.
   */

  tcb->flags = TCB_FLAG_TTYPE_KERNEL | TCB_FLAG_CUSTOM_STACK;

  /* Allocate the custom stack for the new kernel thread.
   *
   * Do whatever it takes to get a reference to the custom stack.
   * Here custom_alloc() is used as a placeholder for whatever
   * that may be.
   */

  stack = (FAR uint32_t *)custom_alloc(stacksize);
  if (stack == NULL)
    {
      kmm_free(tcb);
      return -ENOMEM;
    }

  /* Initialize the TCB.  This will initialize all remaining
   * fields of the TCB, associate the stack to the TCB, allocate
   * any additional resources needed by the taskernelkernel thread, and
   * place the TCB in a list of inactive tasks.
   */

  ret = task_init((FAR struct tcb_s *)tcb, progname, priority,
                  stack, stacksize, entry_point, argv);
  if (ret < 0)
    {
      kmm_free(tcb);
      custom_free(stack);
      return ret;
    }

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