5f5d5496d9
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@165 42af7a65-404d-4744-a932-0658087f49c3
279 lines
8.7 KiB
C
279 lines
8.7 KiB
C
/************************************************************
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* mq_receive.c
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*
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* Copyright (C) 2007 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
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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 Gregory Nutt 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 <sys/types.h> /* uint32, etc. */
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#include <stdarg.h> /* va_list */
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#include <unistd.h>
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#include <fcntl.h> /* O_NONBLOCK */
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#include <string.h>
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#include <assert.h>
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#include <errno.h>
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#include <mqueue.h>
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#include <sched.h>
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#include <debug.h>
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#include <nuttx/kmalloc.h>
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#include <nuttx/arch.h>
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#include <nuttx/os_external.h>
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#include "os_internal.h"
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#include "sig_internal.h"
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#include "mq_internal.h"
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/************************************************************
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* Definitions
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************************************************************/
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/************************************************************
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* Private Type Declarations
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************************************************************/
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/************************************************************
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* Global Variables
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************************************************************/
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/************************************************************
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* Private Variables
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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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* Public Functions
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************************************************************/
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/************************************************************
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* Function: mq_receive
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*
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* Description:
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* This function receives the oldest of the highest
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* priority messages from the message queue specified by
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* "mqdes." If the size of the buffer in bytes (msglen) is
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* less than the "mq_msgsize" attribute of the message
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* queue, mq_receive will return an error. Otherwise, the
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* selected message is removed from the queue and copied to
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* "msg."
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*
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* If the message queue is empty and O_NONBLOCK was not
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* set, mq_receive() will block until a message is added
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* to the message queue. If more than one task is waiting
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* to receive a message, only the task with the highest
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* priority that has waited the longest will be unblocked.
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*
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* If the queue is empty and O_NONBLOCK is set, ERROR will
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* be returned.
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*
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* 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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* Return Value:
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* One success, the length of the selected message in bytes.is
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* returned. On failure, -1 (ERROR) is returned and the errno
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* 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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* Assumptions:
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*
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************************************************************/
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int mq_receive(mqd_t mqdes, void *msg, size_t msglen, int *prio)
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{
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FAR _TCB *rtcb;
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FAR _TCB *btcb;
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FAR msgq_t *msgq;
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FAR mqmsg_t *curr;
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irqstate_t saved_state;
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ubyte rcvmsglen;
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int ret = ERROR;
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/* Verify the input parameters */
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if (!msg || !mqdes)
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{
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*get_errno_ptr() = EINVAL;
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return ERROR;
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}
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if ((mqdes->oflags & O_RDOK) == 0)
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{
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*get_errno_ptr() = EPERM;
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return ERROR;
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}
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if (msglen < (size_t)mqdes->msgq->maxmsgsize)
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{
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*get_errno_ptr() = EMSGSIZE;
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return ERROR;
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}
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/* Get a pointer to the message queue */
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sched_lock();
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msgq = mqdes->msgq;
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/* Several operations must be performed below: We must determine if
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* a message is pending and, if not, wait for the message. Since
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* messages can be sent from the interrupt level, there is a race
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* condition that can only be eliminated by disabling interrupts!
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*/
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saved_state = irqsave();
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/* Get the message from the head of the queue */
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while ((curr = (FAR mqmsg_t*)sq_remfirst(&msgq->msglist)) == NULL)
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{
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/* Should we block until there the above condition has been
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* satisfied?
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*/
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if (!(mqdes->oflags & O_NONBLOCK))
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{
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/* Block and try again */
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rtcb = (FAR _TCB*)g_readytorun.head;
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rtcb->msgwaitq = msgq;
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msgq->nwaitnotempty++;
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*get_errno_ptr() = OK;
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up_block_task(rtcb, TSTATE_WAIT_MQNOTEMPTY);
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/* When we resume at this point, either (1) the message queue
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* is no longer empty, or (2) the wait has been interrupted by
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* a signal. We can detect the latter case be examining the
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* errno value (should be EINTR).
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*/
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if (*get_errno_ptr() != OK)
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{
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break;
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}
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}
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else
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{
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/* The queue was empty, and the O_NONBLOCK flag was set for the
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* message queue description referred to by 'mqdes'.
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*/
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*get_errno_ptr() = EAGAIN;
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break;
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}
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}
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/* If we got message, then decrement the number of messages in
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* the queue while we are still in the critical section
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*/
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if (curr)
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{
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msgq->nmsgs--;
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}
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irqrestore(saved_state);
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/* Check (again) if we got a message from the message queue*/
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if (curr)
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{
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/* Get the length of the message (also the return value) */
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ret = rcvmsglen = curr->msglen;
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/* Copy the message into the caller's buffer */
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memcpy(msg, (const void*)curr->mail, rcvmsglen);
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/* Copy the message priority as well (if a buffer is provided) */
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if (prio)
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{
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*prio = curr->priority;
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}
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/* We are done with the message. Deallocate it now. */
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mq_msgfree(curr);
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/* Check if any tasks are waiting for the MQ not full event. */
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if (msgq->nwaitnotfull > 0)
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{
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/* Find the highest priority task that is waiting for
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* this queue to be not-full in g_waitingformqnotfull list.
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* This must be performed in a critical section because
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* messages can be sent from interrupt handlers.
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*/
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saved_state = irqsave();
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for (btcb = (FAR _TCB*)g_waitingformqnotfull.head;
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btcb && btcb->msgwaitq != msgq;
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btcb = btcb->flink);
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/* If one was found, unblock it. NOTE: There is a race
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* condition here: the queue might be full again by the
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* time the task is unblocked
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*/
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if (!btcb)
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{
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PANIC(OSERR_MQNOTFULLCOUNT);
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}
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else
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{
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btcb->msgwaitq = NULL;
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msgq->nwaitnotfull--;
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up_unblock_task(btcb);
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}
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irqrestore(saved_state);
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}
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}
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sched_unlock();
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return ret;
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}
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