nuttx/fs/mqueue/mq_unlink.c

/****************************************************************************
 * fs/mqueue/mq_unlink.c
 *
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.  The
 * ASF licenses this file to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance with the
 * License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
 * License for the specific language governing permissions and limitations
 * under the License.
 *
 ****************************************************************************/

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

#include <nuttx/config.h>

#include <stdbool.h>
#include <stdio.h>
#include <mqueue.h>
#include <assert.h>
#include <errno.h>

#include <nuttx/mqueue.h>

#include "inode/inode.h"
#include "mqueue/mqueue.h"

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

/****************************************************************************
 * Name: mq_inode_release
 *
 * Description:
 *   Release a reference count on a message queue inode.
 *
 * Input Parameters:
 *   inode - The message queue inode
 *
 * Returned Value:
 *   None
 *
 ****************************************************************************/

static void mq_inode_release(FAR struct inode *inode)
{
  if (inode->i_crefs <= 1)
    {
      FAR struct mqueue_inode_s *msgq = inode->i_private;

      if (msgq)
        {
          nxmq_free_msgq(msgq);
          inode->i_private = NULL;
        }

      inode_release(inode);
    }
}

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

/****************************************************************************
 * Name: file_mq_unlink
 *
 * Description:
 *   This is an internal OS interface.  It is functionally equivalent to
 *   mq_unlink() except that:
 *
 *   - It is not a cancellation point, and
 *   - It does not modify the errno value.
 *
 *  See comments with mq_unlink() for a more complete description of the
 *  behavior of this function
 *
 * Input Parameters:
 *   mq_name - Name of the message queue
 *
 * Returned Value:
 *   This is an internal OS interface and should not be used by applications.
 *   It follows the NuttX internal error return policy:  Zero (OK) is
 *   returned on success. A negated errno value is returned on failure.
 *
 ****************************************************************************/

int file_mq_unlink(FAR const char *mq_name)
{
  FAR struct inode *inode;
  struct inode_search_s desc;
  char fullpath[MAX_MQUEUE_PATH];
  int ret;

  /* Get the full path to the message queue */

  snprintf(fullpath, MAX_MQUEUE_PATH,
           CONFIG_FS_MQUEUE_VFS_PATH "/%s", mq_name);

  /* Get the inode for this message queue. */

  SETUP_SEARCH(&desc, fullpath, false);

  sched_lock();
  ret = inode_find(&desc);
  if (ret < 0)
    {
      /* There is no inode that includes in this path */

      goto errout_with_search;
    }

  /* Get the search results */

  inode = desc.node;
  DEBUGASSERT(inode != NULL);

  /* Verify that what we found is, indeed, a message queue */

  if (!INODE_IS_MQUEUE(inode))
    {
      ret = -ENXIO;
      goto errout_with_inode;
    }

  /* Refuse to unlink the inode if it has children.  I.e., if it is
   * functioning as a directory and the directory is not empty.
   */

  ret = inode_semtake();
  if (ret < 0)
    {
      goto errout_with_inode;
    }

  if (inode->i_child != NULL)
    {
      ret = -ENOTEMPTY;
      goto errout_with_semaphore;
    }

  /* Remove the old inode from the tree.  Because we hold a reference count
   * on the inode, it will not be deleted now.  This will set the
   * FSNODEFLAG_DELETED bit in the inode flags.
   */

  ret = inode_remove(fullpath);

  /* inode_remove() should always fail with -EBUSY because we hae a reference
   * on the inode.  -EBUSY means that the inode was, indeed, unlinked but
   * thatis could not be freed because there are references.
   */

  DEBUGASSERT(ret >= 0 || ret == -EBUSY);

  /* Now we do not release the reference count in the normal way (by calling
   * inode release.  Rather, we call mq_inode_release().  mq_inode_release
   * will decrement the reference count on the inode.  But it will also free
   * the message queue if that reference count decrements to zero.  Since we
   * hold one reference, that can only occur if the message queue is not
   * in-use.
   */

  inode_semgive();
  mq_inode_release(inode);
  RELEASE_SEARCH(&desc);
  sched_unlock();
  return OK;

errout_with_semaphore:
  inode_semgive();

errout_with_inode:
  inode_release(inode);

errout_with_search:
  RELEASE_SEARCH(&desc);
  sched_unlock();
  return ret;
}

/****************************************************************************
 * Name: nxmq_unlink
 *
 * Description:
 *   This is an internal OS interface.  It is functionally equivalent to
 *   mq_unlink() except that:
 *
 *   - It is not a cancellation point, and
 *   - It does not modify the errno value.
 *
 *  See comments with mq_unlink() for a more complete description of the
 *  behavior of this function
 *
 * Input Parameters:
 *   mq_name - Name of the message queue
 *
 * Returned Value:
 *   This is an internal OS interface and should not be used by applications.
 *   It follows the NuttX internal error return policy:  Zero (OK) is
 *   returned on success. A negated errno value is returned on failure.
 *
 ****************************************************************************/

int nxmq_unlink(FAR const char *mq_name)
{
  return file_mq_unlink(mq_name);
}

/****************************************************************************
 * Name: mq_unlink
 *
 * Description:
 *   This function removes the message queue named by "mq_name." If one
 *   or more tasks have the message queue open when mq_unlink() is called,
 *   removal of the message queue is postponed until all references to the
 *   message queue have been closed.
 *
 * Input Parameters:
 *   mq_name - Name of the message queue
 *
 * Returned Value:
 *   None
 *
 * Assumptions:
 *
 ****************************************************************************/

int mq_unlink(FAR const char *mq_name)
{
  int ret;

  ret = nxmq_unlink(mq_name);
  if (ret < 0)
    {
      set_errno(-ret);
      return ERROR;
    }

  return OK;
}