The Asynch I/O implementation now satisfies POSIX priority requirements; it uses the new low priority worker thread interfaces to adjust the priority of the worker thread according to the priority of the client thread
This commit is contained in:
Gregory Nutt
parent
dd2c94d593
commit
98a4b6fb79
37
TODO
37
TODO
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@ -1,4 +1,4 @@
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NuttX TODO List (Last updated October 6, 2014)
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NuttX TODO List (Last updated October 7, 2014)
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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This file summarizes known NuttX bugs, limitations, inconsistencies with
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@ -18,7 +18,7 @@ nuttx/
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(13) Network (net/, drivers/net)
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(4) USB (drivers/usbdev, drivers/usbhost)
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(10) Libraries (libc/, )
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(13) File system/Generic drivers (fs/, drivers/)
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(12) File system/Generic drivers (fs/, drivers/)
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(6) Graphics subystem (graphics/)
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(1) Pascal add-on (pcode/)
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(1) Documentation (Documentation/)
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@ -1163,39 +1163,6 @@ o File system / Generic drivers (fs/, drivers/)
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Status: Open
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Priority: Medium
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Title: ASYNCHRONOUS I/O IMPLEMENTATION PRIORITY ISSUES
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Description: The POSIX specification of asynchronous I/O implies that a
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thread is created for each I/O operation. The standard
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requires that if prioritized I/O is supported for this file,
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then the asynchronous operation will be submitted at a
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priority equal to a base scheduling priority minus
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aiocbp->aio_reqprio. If Thread Execution Scheduling is not
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supported, then the base scheduling priority is that of the
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calling thread.
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My initial gut feeling is the creating a new thread on each
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asynchronous I/O operation would not be a good use of resources
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in a deeply embedded system. So I decided to execute all
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asynchronous I/O on a low-priority or user-space worker
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thread. There are two negative consequences of this decision
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that need to be revisited:
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1) The worker thread runs at a fixed priority making it
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impossible to meet the POSIX requirement for asynchronous
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I/O. That standard specifically requires varying priority.
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2) On the worker thread, each I/O will still be performed
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synchronously, one at a time. This is not a violation of
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the POSIX requirement, but one would think there could be
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opportunities for concurrent I/O.
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In reality, in a small embedded system, there will probably
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only be one real file system and, in this case, the I/O will
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be performed sequentially anyway. Most simple embedded
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hardware will not support any concurrent accesses.
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Status: Open
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Priority: Low, I think. In fact the current solution might be the
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correct one but this issue still needs to be tracked.
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Title: ASYNCHRONOUX I/O DOES NOT WORK WITH SOCKETS
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Description: The current asynchronous I/O logic will only work with
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file descriptions. If given a socket descriptor, the
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@ -37,8 +37,8 @@ ifeq ($(CONFIG_FS_AIO),y)
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# Add the asynchronous I/O C files to the build
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CSRCS += aio_cancel.c aioc_contain.c aio_fsync.c aio_initialize.c aio_read.c
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CSRCS += aio_signal.c aio_write.c
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CSRCS += aio_cancel.c aioc_contain.c aio_fsync.c aio_initialize.c
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CSRCS += aio_queue.c aio_read.c aio_signal.c aio_write.c
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# Add the asynchronous I/O directory to the build
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20
fs/aio/aio.h
20
fs/aio/aio.h
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@ -76,7 +76,9 @@ struct aio_container_s
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FAR struct file *aioc_filep; /* File structure to use with the I/O */
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struct work_s aioc_work; /* Used to defer I/O to the work thread */
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pid_t aioc_pid; /* ID of the waiting task */
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#ifdef CONFIG_PRIORITY_INHERITANCE
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uint8_t aioc_prio; /* Priority of the waiting task */
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#endif
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};
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/****************************************************************************
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@ -211,6 +213,24 @@ FAR struct aio_container_s *aio_contain(FAR struct aiocb *aiocbp);
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FAR struct aiocb *aioc_decant(FAR struct aio_container_s *aioc);
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/****************************************************************************
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* Name: aio_queue
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*
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* Description:
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* Schedule the asynchronous I/O on the low priority work queue
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*
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* Input Parameters:
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* arg - Worker argument. In this case, a pointer to an instance of
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* struct aiocb cast to void *.
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*
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* Returned Value:
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* Zero (OK) on success. Otherwise, -1 is returned and the errno is set
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* appropriately.
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*
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****************************************************************************/
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int aio_queue(FAR struct aio_container_s *aioc, worker_t worker);
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/****************************************************************************
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* Name: aio_signal
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*
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@ -46,7 +46,6 @@
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#include <errno.h>
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#include <debug.h>
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#include <nuttx/wqueue.h>
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#include <nuttx/fs/fs.h>
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#include "aio/aio.h"
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@ -94,6 +93,9 @@ static void aio_fsync_worker(FAR void *arg)
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FAR struct aio_container_s *aioc = (FAR struct aio_container_s *)arg;
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FAR struct aiocb *aiocbp;
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pid_t pid;
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#ifdef CONFIG_PRIORITY_INHERITANCE
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uint8_t prio;
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#endif
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int ret;
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/* Get the information from the container, decant the AIO control block,
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@ -103,6 +105,9 @@ static void aio_fsync_worker(FAR void *arg)
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DEBUGASSERT(aioc && aioc->aioc_aiocbp);
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pid = aioc->aioc_pid;
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#ifdef CONFIG_PRIORITY_INHERITANCE
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prio = aioc->aioc_prio;
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#endif
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aiocbp = aioc_decant(aioc);
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/* Perform the fsync using aioc_filep */
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@ -123,6 +128,12 @@ static void aio_fsync_worker(FAR void *arg)
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/* Signal the client */
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(void)aio_signal(pid, aiocbp);
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#ifdef CONFIG_PRIORITY_INHERITANCE
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/* Restore the low priority worker thread default priority */
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lpwork_restorepriority(prio);
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#endif
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}
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/****************************************************************************
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@ -235,11 +246,11 @@ int aio_fsync(int op, FAR struct aiocb *aiocbp)
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/* Defer the work to the worker thread */
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ret = work_queue(LPWORK, &aioc->aioc_work, aio_fsync_worker, aioc, 0);
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ret = aio_queue(aioc, aio_fsync_worker);
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if (ret < 0)
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{
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aiocbp->aio_result = ret;
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set_errno(ret);
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/* The result and the errno have already been set */
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return ERROR;
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}
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@ -0,0 +1,126 @@
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/****************************************************************************
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* fs/aio/aio_queue.c
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*
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* Copyright (C) 2014 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 <sched.h>
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#include <aio.h>
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#include <errno.h>
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#include <debug.h>
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#include <nuttx/wqueue.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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* Pre-processor Definitions
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****************************************************************************/
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/****************************************************************************
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* Private Types
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****************************************************************************/
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/****************************************************************************
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* Private Data
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****************************************************************************/
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/****************************************************************************
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* Public Data
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****************************************************************************/
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: aio_queue
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*
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* Description:
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* Schedule the asynchronous I/O on the low priority work queue
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*
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* Input Parameters:
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* arg - Worker argument. In this case, a pointer to an instance of
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* struct aiocb cast to void *.
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*
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* Returned Value:
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* Zero (OK) on success. Otherwise, -1 is returned and the errno is set
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* appropriately.
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*
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****************************************************************************/
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int aio_queue(FAR struct aio_container_s *aioc, worker_t worker)
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{
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int ret;
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#ifdef CONFIG_PRIORITY_INHERITANCE
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/* Prohibit context switches until we complete the queuing */
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sched_lock();
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/* Make sure that the low-priority worker thread is running at at least
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* the priority specified for this action.
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*/
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lpwork_boostpriority(aioc->aioc_prio);
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#endif
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/* Schedule the work on the low priority worker thread */
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ret = work_queue(LPWORK, &aioc->aioc_work, worker, aioc, 0);
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if (ret < 0)
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{
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FAR struct aiocb *aiocbp = aioc->aioc_aiocbp;
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DEBUGASSERT(aiocbp);
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aiocbp->aio_result = ret;
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set_errno(-ret);
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ret = ERROR;
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}
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#ifdef CONFIG_PRIORITY_INHERITANCE
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/* Now the low-priority work queue might run at its new priority */
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sched_unlock();
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#endif
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return ret;
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}
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#endif /* CONFIG_FS_AIO */
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@ -46,8 +46,6 @@
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#include <errno.h>
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#include <debug.h>
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#include <nuttx/wqueue.h>
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#include "aio/aio.h"
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#ifdef CONFIG_FS_AIO
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@ -93,6 +91,9 @@ static void aio_read_worker(FAR void *arg)
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FAR struct aio_container_s *aioc = (FAR struct aio_container_s *)arg;
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FAR struct aiocb *aiocbp;
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pid_t pid;
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#ifdef CONFIG_PRIORITY_INHERITANCE
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uint8_t prio;
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#endif
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ssize_t nread;
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/* Get the information from the container, decant the AIO control block,
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@ -102,6 +103,9 @@ static void aio_read_worker(FAR void *arg)
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DEBUGASSERT(aioc && aioc->aioc_aiocbp);
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pid = aioc->aioc_pid;
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#ifdef CONFIG_PRIORITY_INHERITANCE
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prio = aioc->aioc_prio;
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#endif
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aiocbp = aioc_decant(aioc);
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/* Perform the read using:
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@ -132,6 +136,12 @@ static void aio_read_worker(FAR void *arg)
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/* Signal the client */
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(void)aio_signal(pid, aiocbp);
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#ifdef CONFIG_PRIORITY_INHERITANCE
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/* Restore the low priority worker thread default priority */
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lpwork_restorepriority(prio);
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#endif
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}
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/****************************************************************************
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@ -281,11 +291,11 @@ int aio_read(FAR struct aiocb *aiocbp)
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/* Defer the work to the worker thread */
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ret = work_queue(LPWORK, &aioc->aioc_work, aio_read_worker, aioc, 0);
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ret = aio_queue(aioc, aio_read_worker);
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if (ret < 0)
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{
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aiocbp->aio_result = ret;
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set_errno(ret);
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/* The result and the errno have already been set */
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return ERROR;
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}
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@ -48,8 +48,6 @@
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#include <errno.h>
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#include <debug.h>
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#include <nuttx/wqueue.h>
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#include "aio/aio.h"
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#ifdef CONFIG_FS_AIO
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@ -110,6 +108,9 @@ static void aio_write_worker(FAR void *arg)
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FAR struct aio_container_s *aioc = (FAR struct aio_container_s *)arg;
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FAR struct aiocb *aiocbp;
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pid_t pid;
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#ifdef CONFIG_PRIORITY_INHERITANCE
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uint8_t prio;
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#endif
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ssize_t nwritten;
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int oflags;
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@ -120,6 +121,9 @@ static void aio_write_worker(FAR void *arg)
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DEBUGASSERT(aioc && aioc->aioc_aiocbp);
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pid = aioc->aioc_pid;
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#ifdef CONFIG_PRIORITY_INHERITANCE
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prio = aioc->aioc_prio;
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#endif
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aiocbp = aioc_decant(aioc);
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/* Call fcntl(F_GETFL) to get the file open mode. */
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@ -177,6 +181,12 @@ static void aio_write_worker(FAR void *arg)
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/* Signal the client */
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(void)aio_signal(pid, aiocbp);
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#ifdef CONFIG_PRIORITY_INHERITANCE
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/* Restore the low priority worker thread default priority */
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lpwork_restorepriority(prio);
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#endif
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}
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/****************************************************************************
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@ -328,11 +338,11 @@ int aio_write(FAR struct aiocb *aiocbp)
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/* Defer the work to the worker thread */
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ret = work_queue(LPWORK, &aioc->aioc_work, aio_write_worker, aioc, 0);
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ret = aio_queue(aioc, aio_write_worker);
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if (ret < 0)
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{
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aiocbp->aio_result = ret;
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set_errno(ret);
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/* The result and the errno have already been set */
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return ERROR;
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}
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