text: /****************************************************************************
   * nuttx/graphics/nxterm/nxterm_sem.c
   *
   *   Copyright (C) 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:
   *
   * 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 <unistd.h>
  #include <semaphore.h>
  #include <assert.h>
  #include <errno.h>
  
  #include "nxterm.h"
  
  #ifdef CONFIG_DEBUG_FEATURES
  
  /****************************************************************************
   * Public Functions
   ****************************************************************************/
  
  /****************************************************************************
   * Name: nxterm_semwait and nxterm_sempost
   *
   * Description:
   *   If debug is on, then lower level code may attempt console output while
   *   we are doing console output!  In this case, we will toss the nested
   *   output to avoid deadlocks and infinite loops.
   *
   * Input Parameters:
   *   priv - Driver data structure
   *
   * Returned Value:
   *
   *
   ****************************************************************************/
  
  int nxterm_semwait(FAR struct nxterm_state_s *priv)
  {
    pid_t me;
    int ret;
  
    /* Does I already hold the semaphore */
  
    me = getpid();
    if (priv->holder != me)
      {
        /* No.. then wait until the thread that does hold it is finished with it */
  
        ret = sem_wait(&priv->exclsem);
        if (ret == OK)
          {
            /* No I hold the semaphore */
  
            priv->holder = me;
          }
        return ret;
      }
  
    /* Abort, abort, abort!  I have been re-entered */
  
    set_errno(EBUSY);
    return ERROR;
  }
  
  int nxterm_sempost(FAR struct nxterm_state_s *priv)
  {
    pid_t me = getpid();
  
    /* Make sure that I really hold the semaphore */
  
    ASSERT(priv->holder == me);
  
    /* Then let go of it */
  
    priv->holder = NO_HOLDER;
    return sem_post(&priv->exclsem);
  }
  
  #endif /* CONFIG_DEBUG_FEATURES */
  