265 lines
7.2 KiB
C
265 lines
7.2 KiB
C
/****************************************************************************
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* fs/aio/aio_initialize.c
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*
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* Copyright (C) 2014, 2017 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <gnutt@nuttx.org>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <assert.h>
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#include <errno.h>
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#include <queue.h>
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#include <nuttx/sched.h>
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#include <nuttx/semaphore.h>
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#include "aio/aio.h"
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#ifdef CONFIG_FS_AIO
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/****************************************************************************
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* Private Data
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****************************************************************************/
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/* This is an array of pre-allocated AIO containers */
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static struct aio_container_s g_aioc_alloc[CONFIG_FS_NAIOC];
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/* This is a list of free AIO containers */
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static dq_queue_t g_aioc_free;
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/* This counting semaphore tracks the number of free AIO containers */
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static sem_t g_aioc_freesem;
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/* This binary semaphore supports exclusive access to the list of pending
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* asynchronous I/O. g_aio_holder and a_aio_count support the reentrant
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* lock.
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*/
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static sem_t g_aio_exclsem;
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static pid_t g_aio_holder;
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static uint16_t g_aio_count;
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/****************************************************************************
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* Public Data
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****************************************************************************/
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/* This is a list of pending asynchronous I/O. The user must hold the
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* lock on this list in order to access the list.
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*/
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dq_queue_t g_aio_pending;
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: aio_initialize
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*
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* Description:
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* Perform one-time initialization of the asynchronous I/O sub-system
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*
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* Input Parameters:
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* None
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*
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* Returned Value:
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* None
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*
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****************************************************************************/
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void aio_initialize(void)
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{
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int i;
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/* Initialize counting semaphores */
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nxsem_init(&g_aioc_freesem, 0, CONFIG_FS_NAIOC);
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nxsem_setprotocol(&g_aioc_freesem, SEM_PRIO_NONE);
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nxsem_init(&g_aio_exclsem, 0, 1);
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g_aio_holder = INVALID_PROCESS_ID;
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/* Initialize the container queues */
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dq_init(&g_aioc_free);
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dq_init(&g_aio_pending);
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/* Add all of the pre-allocated AIO containers to the free list */
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for (i = 0; i < CONFIG_FS_NAIOC; i++)
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{
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/* Add the container to the free list */
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dq_addlast(&g_aioc_alloc[i].aioc_link, &g_aioc_free);
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}
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}
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/****************************************************************************
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* Name: aio_lock/aio_unlock
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*
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* Description:
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* Take/give the lock on the pending asynchronous I/O list
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*
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* Input Parameters:
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* None
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*
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* Returned Value:
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* None
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*
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****************************************************************************/
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void aio_lock(void)
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{
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pid_t me = getpid();
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/* Does this thread already hold the semaphore? */
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if (g_aio_holder == me)
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{
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/* Yes, just increment the counts held */
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DEBUGASSERT(g_aio_count > 0 && g_aio_count < UINT16_MAX);
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g_aio_count++;
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}
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else
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{
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nxsem_wait_uninterruptible(&g_aio_exclsem);
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/* And mark it as ours */
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g_aio_holder = me;
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g_aio_count = 1;
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}
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}
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void aio_unlock(void)
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{
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DEBUGASSERT(g_aio_holder == getpid() && g_aio_count > 0);
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/* Would decrementing the count release the lock? */
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if (g_aio_count <= 1)
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{
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/* Yes.. that we will no longer be the holder */
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g_aio_holder = INVALID_PROCESS_ID;
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g_aio_count = 0;
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nxsem_post(&g_aio_exclsem);
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}
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else
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{
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/* Otherwise, just decrement the count. We still hold the lock. */
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g_aio_count--;
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}
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}
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/****************************************************************************
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* Name: aioc_alloc
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*
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* Description:
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* Allocate a new AIO container by taking the next, pre-allocated
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* container from the free list. This function will wait until
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* aioc_free() is called in the event that there is no free container
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* available in the free list.
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*
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* Input Parameters:
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* None
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*
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* Returned Value:
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* A reference to the allocated AIO container. This allocation never
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* fails because the logic will wait in the event that there is no free
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* container.
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*
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****************************************************************************/
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FAR struct aio_container_s *aioc_alloc(void)
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{
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FAR struct aio_container_s *aioc;
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/* Take a count from semaphore, thus guaranteeing that we have an AIO
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* container set aside for us.
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*/
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nxsem_wait_uninterruptible(&g_aioc_freesem);
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/* Get our AIO container */
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aio_lock();
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aioc = (FAR struct aio_container_s *)dq_remfirst(&g_aioc_free);
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aio_unlock();
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DEBUGASSERT(aioc);
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return aioc;
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}
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/****************************************************************************
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* Name: aioc_free
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*
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* Description:
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* Free an AIO container by returning it to the free list and, perhaps,
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* awakening any threads waiting for that resource
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*
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* Input Parameters:
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* aioc - The AIO container to be free
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*
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* Returned Value:
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* None
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*
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****************************************************************************/
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void aioc_free(FAR struct aio_container_s *aioc)
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{
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DEBUGASSERT(aioc);
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/* Return the container to the free list */
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aio_lock();
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dq_addlast(&aioc->aioc_link, &g_aioc_free);
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aio_unlock();
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/* The post the counting semaphore, announcing the availability of the
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* free AIO container.
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*/
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nxsem_post(&g_aioc_freesem);
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}
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#endif /* CONFIG_FS_AIO */
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