/**************************************************************************** * sched/mq_timedreceive.c * * Copyright (C) 2007-2009, 2011 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 "clock_internal.h" #include "mq_internal.h" /**************************************************************************** * Pre-processor 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_t 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) { /* Restart with task with a timeout error */ mq_waitirq(wtcb, ETIMEDOUT); } /* Interrupts may now be re-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() == false); /* 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. */ wdog = wd_create(); if (!wdog) { 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(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; }