/****************************************************************************
* mq_timedreceive.c
*
* Copyright (C) 2007 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* 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 Gregory Nutt 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 <sys/types.h>
#include <unistd.h>
#include <errno.h>
#include <mqueue.h>
#include <wdog.h>
#include <debug.h>
#include <nuttx/arch.h>
#include "os_internal.h"
#include "clock_internal.h"
#include "mq_internal.h"
/****************************************************************************
* Definitions
****************************************************************************/
/****************************************************************************
* Private Type Declarations
****************************************************************************/
/****************************************************************************
* Global Variables
****************************************************************************/
/****************************************************************************
* Private Variables
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Function: mq_rcvtimeout
*
* Description:
* This function is called if the timeout elapses before the message queue
* becomes non-empty.
*
* Parameters:
* argc - the number of arguments (should be 1)
* pid - the task ID of the task to wakeup
*
* Return Value:
* None
*
* Assumptions:
*
****************************************************************************/
static void mq_rcvtimeout(int argc, uint32 pid, ...)
{
FAR _TCB *wtcb;
irqstate_t saved_state;
/* Disable interrupts. This is necessary because an
* interrupt handler may attempt to send a message while we are
* doing this.
*/
saved_state = irqsave();
/* Get the TCB associated with this pid. It is possible that
* task may no longer be active when this watchdog goes off.
*/
wtcb = sched_gettcb((pid_t)pid);
/* It is also possible that an interrupt/context switch beat us to the
* punch and already changed the task's state.
*/
if (wtcb && wtcb->task_state == TSTATE_WAIT_MQNOTEMPTY)
{
/* Mark the errno value for the thread. */
wtcb->errno = ETIMEDOUT;
/* Restart the the task. */
up_unblock_task(wtcb);
}
/* Interrupts may now be enabled. */
irqrestore(saved_state);
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Function: mq_timedreceive
*
* Description:
* This function receives the oldest of the highest
* priority messages from the message queue specified by
* "mqdes." If the size of the buffer in bytes (msglen) is
* less than the "mq_msgsize" attribute of the message
* queue, mq_timedreceive will return an error. Otherwise, the
* selected message is removed from the queue and copied to
* "msg."
*
* If the message queue is empty and O_NONBLOCK was not
* set, mq_timedreceive() will block until a message is added
* to the message queue (or until a timeout occurs). If more
* than one task is waiting to receive a message, only the
* task with the highest priority that has waited the longest
* will be unblocked.
*
* mq_timedreceive() behaves just like mq_receive(), except
* that if the queue is empty and the O_NONBLOCK flag is not
* enabled for the message queue description, then abstime
* points to a structure which specifies a ceiling on the time
* for which the call will block. This ceiling is an absolute
* timeout in seconds and nanoseconds since the Epoch (midnight
* on the morning of 1 January 1970).
*
* If no message is available, and the timeout has already
* expired by the time of the call, mq_timedreceive() returns
* immediately.
*
* Parameters:
* mqdes - Message Queue Descriptor
* msg - Buffer to receive the message
* msglen - Size of the buffer in bytes
* prio - If not NULL, the location to store message priority.
* abstime - the absolute time to wait until a timeout is declared.
*
* Return Value:
* One success, the length of the selected message in bytes.is
* returned. On failure, -1 (ERROR) is returned and the errno
* is set appropriately:
*
* EAGAIN The queue was empty, and the O_NONBLOCK flag was set
* for the message queue description referred to by 'mqdes'.
* EPERM Message queue opened not opened for reading.
* EMSGSIZE 'msglen' was less than the maxmsgsize attribute of the
* message queue.
* EINTR The call was interrupted by a signal handler.
* EINVAL Invalid 'msg' or 'mqdes' or 'abstime'
* ETIMEDOUT The call timed out before a message could be transferred.
*
* Assumptions:
*
****************************************************************************/
ssize_t mq_timedreceive(mqd_t mqdes, void *msg, size_t msglen,
int *prio, const struct timespec *abstime)
{
WDOG_ID wdog;
FAR mqmsg_t *mqmsg;
irqstate_t saved_state;
int ret = ERROR;
DEBUGASSERT(!up_interrupt_context());
/* 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)
{
*get_errno_ptr() = 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.
*/
wdog = wd_create();
if (!wdog)
{
*get_errno_ptr() = 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)
{
sint32 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)
{
*get_errno_ptr() = result;
irqrestore(saved_state);
sched_unlock();
wd_delete(wdog);
return ERROR;
}
/* Start the watchdog */
wd_start(wdog, 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(wdog);
/* 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(wdog);
return ret;
}
