/**************************************************************************** * sched/mq_rcvinternal.c * * Copyright (C) 2007, 2008, 2012 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name NuttX nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /**************************************************************************** * Included Files ****************************************************************************/ #include #include #include #include #include #include #include #include #include #include #include "os_internal.h" #include "mq_internal.h" /**************************************************************************** * Definitions ****************************************************************************/ /**************************************************************************** * Private Type Declarations ****************************************************************************/ /**************************************************************************** * Global Variables ****************************************************************************/ /**************************************************************************** * Private Variables ****************************************************************************/ /**************************************************************************** * Private Functions ****************************************************************************/ /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: mq_verifyreceive * * Description: * This is internal, common logic shared by both mq_receive and * mq_timedreceive. This function verifies the input parameters that are * common to both functions. * * Parameters: * mqdes - Message Queue Descriptor * msg - Buffer to receive the message * msglen - Size of the buffer in bytes * * Return Value: * One success, 0 (OK) is returned. On failure, -1 (ERROR) is returned and * the errno is set appropriately: * * EPERM Message queue opened not opened for reading. * EMSGSIZE 'msglen' was less than the maxmsgsize attribute of the message * queue. * EINVAL Invalid 'msg' or 'mqdes' * * Assumptions: * ****************************************************************************/ int mq_verifyreceive(mqd_t mqdes, void *msg, size_t msglen) { /* Verify the input parameters */ if (!msg || !mqdes) { set_errno(EINVAL); return ERROR; } if ((mqdes->oflags & O_RDOK) == 0) { set_errno(EPERM); return ERROR; } if (msglen < (size_t)mqdes->msgq->maxmsgsize) { set_errno(EMSGSIZE); return ERROR; } return OK; } /**************************************************************************** * Name: mq_waitreceive * * Description: * This is internal, common logic shared by both mq_receive and * mq_timedreceive. This function waits for a message to be received on * the specified message queue, removes the message from the queue, and * returns it. * * Parameters: * mqdes - Message queue descriptor * * Return Value: * On success, a reference to the received message. If the wait was * interrupted by a signal or a timeout, then the errno will be set * appropriately and NULL will be returned. * * Assumptions: * - The caller has provided all validity checking of the input parameters * using mq_verifyreceive. * - Interrupts should be disabled throughout this call. This is necessary * because messages can be sent from interrupt level processing. * - For mq_timedreceive, setting of the timer and this wait must be atomic. * ****************************************************************************/ FAR mqmsg_t *mq_waitreceive(mqd_t mqdes) { FAR _TCB *rtcb; FAR msgq_t *msgq; FAR mqmsg_t *rcvmsg; /* Get a pointer to the message queue */ msgq = mqdes->msgq; /* Get the message from the head of the queue */ while ((rcvmsg = (FAR mqmsg_t*)sq_remfirst(&msgq->msglist)) == NULL) { /* The queue is empty! Should we block until there the above condition * has been satisfied? */ if ((mqdes->oflags & O_NONBLOCK) == 0) { /* Yes.. Block and try again */ rtcb = (FAR _TCB*)g_readytorun.head; rtcb->msgwaitq = msgq; msgq->nwaitnotempty++; set_errno(OK); up_block_task(rtcb, TSTATE_WAIT_MQNOTEMPTY); /* When we resume at this point, either (1) the message queue * is no longer empty, or (2) the wait has been interrupted by * a signal. We can detect the latter case be examining the * errno value (should be either EINTR or ETIMEDOUT). */ if (get_errno() != OK) { break; } } else { /* The queue was empty, and the O_NONBLOCK flag was set for the * message queue description referred to by 'mqdes'. */ set_errno(EAGAIN); break; } } /* If we got message, then decrement the number of messages in * the queue while we are still in the critical section */ if (rcvmsg) { msgq->nmsgs--; } return rcvmsg; } /**************************************************************************** * Name: mq_doreceive * * Description: * This is internal, common logic shared by both mq_receive and * mq_timedreceive. This function accepts the message obtained by * mq_waitmsg, provides the message content to the user, notifies any * threads that were waiting for the message queue to become non-full, * and disposes of the message structure * * Parameters: * mqdes - Message queue descriptor * mqmsg - The message obtained by mq_waitmsg() * ubuffer - The address of the user provided buffer to receive the message * prio - The user-provided location to return the message priority. * * Return Value: * Returns the length of the received message. This function does not fail. * * Assumptions: * - The caller has provided all validity checking of the input parameters * using mq_verifyreceive. * - The user buffer, ubuffer, is known to be large enough to accept the * largest message that an be sent on this message queue * - Pre-emption should be disabled throughout this call. * ****************************************************************************/ ssize_t mq_doreceive(mqd_t mqdes, mqmsg_t *mqmsg, void *ubuffer, int *prio) { FAR _TCB *btcb; irqstate_t saved_state; FAR msgq_t *msgq; ssize_t rcvmsglen; /* Get the length of the message (also the return value) */ rcvmsglen = mqmsg->msglen; /* Copy the message into the caller's buffer */ memcpy(ubuffer, (const void*)mqmsg->mail, rcvmsglen); /* Copy the message priority as well (if a buffer is provided) */ if (prio) { *prio = mqmsg->priority; } /* We are done with the message. Deallocate it now. */ mq_msgfree(mqmsg); /* Check if any tasks are waiting for the MQ not full event. */ msgq = mqdes->msgq; if (msgq->nwaitnotfull > 0) { /* Find the highest priority task that is waiting for * this queue to be not-full in g_waitingformqnotfull list. * This must be performed in a critical section because * messages can be sent from interrupt handlers. */ saved_state = irqsave(); for (btcb = (FAR _TCB*)g_waitingformqnotfull.head; btcb && btcb->msgwaitq != msgq; btcb = btcb->flink); /* If one was found, unblock it. NOTE: There is a race * condition here: the queue might be full again by the * time the task is unblocked */ if (!btcb) { PANIC(OSERR_MQNOTFULLCOUNT); } else { btcb->msgwaitq = NULL; msgq->nwaitnotfull--; up_unblock_task(btcb); } irqrestore(saved_state); } /* Return the length of the message transferred to the user buffer */ return rcvmsglen; }