202 lines
7.0 KiB
C
202 lines
7.0 KiB
C
/****************************************************************************
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* sched/mqueue/mq_receive.c
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*
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* Copyright (C) 2007, 2009, 2016-2017 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 <sys/types.h>
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#include <stdbool.h>
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#include <errno.h>
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#include <mqueue.h>
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#include <debug.h>
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#include <nuttx/irq.h>
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#include <nuttx/arch.h>
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#include <nuttx/mqueue.h>
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#include <nuttx/cancelpt.h>
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#include "mqueue/mqueue.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: nxmq_receive
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*
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* Description:
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* This function receives the oldest of the highest priority messages
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* from the message queue specified by "mqdes." This is an internal OS
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* interface. It is functionally equivalent to mq_receive except that:
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*
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* - It is not a cancellation point, and
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* - It does not modify the errno value.
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*
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* See comments with mq_receive() for a more complete description of the
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* behavior of this function
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*
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* Input Parameters:
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* mqdes - Message Queue Descriptor
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* msg - Buffer to receive the message
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* msglen - Size of the buffer in bytes
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* prio - If not NULL, the location to store message priority.
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*
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* Returned Value:
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* This is an internal OS interface and should not be used by applications.
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* It follows the NuttX internal error return policy: Zero (OK) is
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* returned on success. A negated errno value is returned on failure.
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* (see mq_receive() for the list list valid return values).
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*
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****************************************************************************/
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ssize_t nxmq_receive(mqd_t mqdes, FAR char *msg, size_t msglen,
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FAR unsigned int *prio)
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{
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FAR struct mqueue_msg_s *mqmsg;
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irqstate_t flags;
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ssize_t ret;
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DEBUGASSERT(up_interrupt_context() == false);
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/* Verify the input parameters and, in case of an error, set
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* errno appropriately.
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*/
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ret = nxmq_verify_receive(mqdes, msg, msglen);
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if (ret < 0)
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{
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return ret;
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}
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/* Get the next message from the message queue. We will disable
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* pre-emption until we have completed the message received. This
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* is not too bad because if the receipt takes a long time, it will
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* be because we are blocked waiting for a message and pre-emption
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* will be re-enabled while we are blocked
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*/
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sched_lock();
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/* Furthermore, nxmq_wait_receive() expects to have interrupts disabled
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* because messages can be sent from interrupt level.
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*/
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flags = enter_critical_section();
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/* Get the message from the message queue */
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ret = nxmq_wait_receive(mqdes, &mqmsg);
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leave_critical_section(flags);
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/* Check if we got a message from the message queue. We might
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* not have a message if:
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*
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* - The message queue is empty and O_NONBLOCK is set in the mqdes
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* - The wait was interrupted by a signal
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*/
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if (ret >= 0)
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{
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DEBUGASSERT(mqmsg != NULL);
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ret = nxmq_do_receive(mqdes, mqmsg, msg, prio);
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}
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sched_unlock();
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return ret;
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}
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/****************************************************************************
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* Name: mq_receive
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*
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* Description:
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* This function receives the oldest of the highest priority messages
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* from the message queue specified by "mqdes." If the size of the
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* buffer in bytes (msglen) is less than the "mq_msgsize" attribute of
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* the message queue, mq_receive will return an error. Otherwise, the
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* selected message is removed from the queue and copied to "msg."
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*
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* If the message queue is empty and O_NONBLOCK was not set,
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* mq_receive() will block until a message is added to the message
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* queue. If more than one task is waiting to receive a message, only
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* the task with the highest priority that has waited the longest will
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* be unblocked.
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*
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* If the queue is empty and O_NONBLOCK is set, ERROR will be returned.
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*
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* Input Parameters:
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* mqdes - Message Queue Descriptor
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* msg - Buffer to receive the message
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* msglen - Size of the buffer in bytes
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* prio - If not NULL, the location to store message priority.
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*
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* Returned Value:
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* One success, the length of the selected message in bytes is returned.
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* On failure, -1 (ERROR) is returned and the errno is set appropriately:
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*
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* EAGAIN The queue was empty, and the O_NONBLOCK flag was set
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* for the message queue description referred to by 'mqdes'.
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* EPERM Message queue opened not opened for reading.
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* EMSGSIZE 'msglen' was less than the maxmsgsize attribute of the
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* message queue.
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* EINTR The call was interrupted by a signal handler.
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* EINVAL Invalid 'msg' or 'mqdes'
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*
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****************************************************************************/
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ssize_t mq_receive(mqd_t mqdes, FAR char *msg, size_t msglen,
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FAR unsigned int *prio)
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{
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int ret;
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/* mq_receive() is a cancellation point */
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(void)enter_cancellation_point();
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/* Let nxmq_receive do all of the work */
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ret = nxmq_receive(mqdes, msg, msglen, prio);
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if (ret < 0)
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{
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set_errno(-ret);
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ret = ERROR;
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}
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leave_cancellation_point();
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return ret;
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}
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