libs/libc/aio/aio_suspend.c

/****************************************************************************
 * libs/libc/aio/aio_suspend.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 <sched.h>
#include <signal.h>
#include <aio.h>
#include <assert.h>
#include <errno.h>

#ifdef CONFIG_FS_AIO

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

/****************************************************************************
 * Name: aio_suspend
 *
 * Description:
 *   The aio_suspend() function suspends the calling thread until at least
 *   one of the asynchronous I/O operations referenced by the 'list' argument
 *   has completed, until a signal interrupts the function, or, if 'timeout'
 *   is not NULL, until the time interval specified by 'timeout' has passed.
 *   If any of the aiocb structures in the list correspond to completed
 *   asynchronous I/O operations (that is, the error status for the
 *   operation is not equal to EINPROGRESS) at the time of the call, the
 *   function returns without suspending the calling thread.
 *
 *   Each aiocb structure pointed to must have been used in initiating an
 *   asynchronous I/O request via aio_read(), aio_write(), or lio_listio().
 *   This array may contain NULL pointers, which are ignored. If this
 *   array contains pointers that refer to aiocb structures that have not
 *   been used in submitting asynchronous I/O, the effect is undefined.
 *
 * Input Parameters:
 *   list    - An array of pointers to asynchronous I/O control blocks.
 *   nent    - The number of elements in the array.
 *   aiocbp  - A pointer to an array
 *   timeout - If not NULL, this parameter is pointer to a timespec
 *             structure that determines a timeout on the operation.  If
 *             the time referred to timeout passes before any of the I/O
 *             operations referenced by list are completed, then
 *             aio_suspend() returns with an error.
 *
 * Returned Value:
 *   If the aio_suspend() function returns after one or more asynchronous
 *   I/O operations have completed, the function returns zero. Otherwise,
 *   the function returns a value of -1 and sets errno to indicate the
 *   error.  The application may determine which asynchronous I/O completed
 *   by scanning the associated error and return status using aio_error()
 *   and aio_return(), respectively.
 *
 *   The aio_suspend() function will fail if:
 *
 *     EAGAIN - No asynchronous I/O indicated in the list referenced by
 *              list completed in the time interval indicated by timeout.
 *     EINTR  - A signal interrupted the aio_suspend() function.
 *
 ****************************************************************************/

int aio_suspend(FAR const struct aiocb * const list[], int nent,
                FAR const struct timespec *timeout)
{
  sigset_t set;
  int ret;
  int i;

  DEBUGASSERT(list);

  /* Lock the scheduler so that no I/O events can complete on the worker
   * thread until we set our wait set up.  Pre-emption will, of course, be
   * re-enabled while we are waiting for the signal.
   */

  sched_lock();

  /* Check each entry in the list.  Break out of the loop if any entry
   * has completed.
   */

  for (i = 0; i < nent; i++)
    {
      /* Check if the I/O has completed */

      if (list[i] && list[i]->aio_result != -EINPROGRESS)
        {
          /* Yes, return success */

          sched_unlock();
          return OK;
        }
    }

  /* Then wait for SIGPOLL.  On success sigtimedwait() will return the
   * signal number that cause the error (SIGPOLL).  It will set errno
   * appropriately for this function on errors.
   *
   * NOTE: If completion of the I/O causes other signals to be generated
   * first, then this will wake up and return EINTR instead of success.
   */

  sigemptyset(&set);
  sigaddset(&set, SIGPOLL);

  ret = sigtimedwait(&set, NULL, timeout);
  sched_unlock();
  return ret >= 0 ? OK : ERROR;
}

#endif /* CONFIG_FS_AIO */