ssize_t mq_receive(mqd_t mqdes, FAR char *msg, size_t msglen,
FAR int *prio)
{
FAR struct mqueue_msg_s *mqmsg;
irqstate_t saved_state;
ssize_t ret = ERROR;
DEBUGASSERT(up_interrupt_context() == false);
/* Verify the input parameters and, in case of an error, set
* errno appropriately.
*/
if (mq_verifyreceive(mqdes, msg, msglen) != OK)
{
return ERROR;
}
/* Get the next message from the message queue. We will disable
* pre-emption until we have completed the message received. This
* is not too bad because if the receipt takes a long time, it will
* be because we are blocked waiting for a message and pre-emption
* will be re-enabled while we are blocked
*/
sched_lock();
/* Furthermore, mq_waitreceive() expects to have interrupts disabled
* because messages can be sent from interrupt level.
*/
saved_state = irqsave();
/* Get the message from the message queue */
mqmsg = mq_waitreceive(mqdes);
irqrestore(saved_state);
/* Check if we got a message from the message queue. We might
* not have a message if:
*
* - The message queue is empty and O_NONBLOCK is set in the mqdes
* - The wait was interrupted by a signal
*/
if (mqmsg)
{
ret = mq_doreceive(mqdes, mqmsg, msg, prio);
}
sched_unlock();
return ret;
}
ssize_t mq_timedreceive(mqd_t mqdes, void *msg, size_t msglen,
int *prio, const struct timespec *abstime)
{
FAR struct tcb_s *rtcb = (FAR struct tcb_s *)g_readytorun.head;
FAR mqmsg_t *mqmsg;
irqstate_t saved_state;
int ret = ERROR;
DEBUGASSERT(up_interrupt_context() == false && rtcb->waitdog == NULL);
/* Verify the input parameters and, in case of an error, set
* errno appropriately.
*/
if (mq_verifyreceive(mqdes, msg, msglen) != OK)
{
return ERROR;
}
if (!abstime || abstime->tv_sec < 0 || abstime->tv_nsec > 1000000000)
{
set_errno(EINVAL);
return ERROR;
}
/* Create a watchdog. We will not actually need this watchdog
* unless the queue is not empty, but we will reserve it up front
* before we enter the following critical section.
*/
rtcb->waitdog = wd_create();
if (!rtcb->waitdog)
{
set_errno(EINVAL);
return ERROR;
}
/* Get the next mesage from the message queue. We will disable
* pre-emption until we have completed the message received. This
* is not too bad because if the receipt takes a long time, it will
* be because we are blocked waiting for a message and pre-emption
* will be re-enabled while we are blocked
*/
sched_lock();
/* Furthermore, mq_waitreceive() expects to have interrupts disabled
* because messages can be sent from interrupt level.
*/
saved_state = irqsave();
/* Check if the message queue is empty. If it is NOT empty, then we
* will not need to start timer.
*/
if (mqdes->msgq->msglist.head == NULL)
{
int ticks;
/* Convert the timespec to clock ticks. We must have interrupts
* disabled here so that this time stays valid until the wait begins.
*/
int result = clock_abstime2ticks(CLOCK_REALTIME, abstime, &ticks);
/* If the time has already expired and the message queue is empty,
* return immediately.
*/
if (result == OK && ticks <= 0)
{
result = ETIMEDOUT;
}
/* Handle any time-related errors */
if (result != OK)
{
set_errno(result);
irqrestore(saved_state);
sched_unlock();
wd_delete(rtcb->waitdog);
rtcb->waitdog = NULL;
return ERROR;
}
/* Start the watchdog */
wd_start(rtcb->waitdog, ticks, (wdentry_t)mq_rcvtimeout, 1, getpid());
}
/* Get the message from the message queue */
mqmsg = mq_waitreceive(mqdes);
/* Stop the watchdog timer (this is not harmful in the case where
* it was never started)
*/
wd_cancel(rtcb->waitdog);
/* We can now restore interrupts */
irqrestore(saved_state);
/* Check if we got a message from the message queue. We might
* not have a message if:
*
* - The message queue is empty and O_NONBLOCK is set in the mqdes
* - The wait was interrupted by a signal
* - The watchdog timeout expired
*/
if (mqmsg)
{
ret = mq_doreceive(mqdes, mqmsg, msg, prio);
}
sched_unlock();
wd_delete(rtcb->waitdog);
rtcb->waitdog = NULL;
return ret;
}
