nuttx/sched/get_errno_ptr.c

/************************************************************
 * get_errno_ptr.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 <sched.h>
#include <errno.h>
#include <nuttx/arch.h>
#include "os_internal.h"

#undef get_errno_ptr

/************************************************************
 * Private Data
 ************************************************************/

static int g_irqerrno;

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

/************************************************************
 * Function:  get_errno_ptr
 *
 * Description:
 *   Return a pointer to the thread specific errno.
 *
 * Parameters:
 *   None
 *
 * Return Value:
 *   A pointer to the per-thread errno variable.
 *
 * Assumptions:
 *
 ************************************************************/

FAR int *get_errno_ptr(void)
{
  /* Check if this function was called from an interrupt
   * handler.  In that case, we have to do things a little
   * differently.
   */

  if (up_interrupt_context())
    {
      /* Yes, we were called from an interrupt handler.  Do
       * not permit access to the errno in the TCB of the
       * interrupt task.  Instead, use a separate errno just
       * for interrupt handlers.  Of course, this would have
       * to change if we ever wanted to support nested
       * interrupts.
       */

      return &g_irqerrno;
    }
  else
    {
      /* We were called from the normal tasking context.  Return
       * a reference to the thread-private errno in the TCB.
       */

      FAR _TCB *ptcb = (FAR _TCB*)g_readytorun.head;
      return &ptcb->errno;
    }
}