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Diffstat (limited to 'nuttx/sched/mq_receive.c')
| -rw-r--r-- | nuttx/sched/mq_receive.c | 236 |
1 files changed, 236 insertions, 0 deletions
diff --git a/nuttx/sched/mq_receive.c b/nuttx/sched/mq_receive.c new file mode 100644 index 0000000000..3dbe662c2f --- /dev/null +++ b/nuttx/sched/mq_receive.c @@ -0,0 +1,236 @@ +/************************************************************ + * mq_receive.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> /* uint32, etc. */ +#include <stdarg.h> /* va_list */ +#include <unistd.h> +#include <string.h> +#include <assert.h> +#include <mqueue.h> +#include <sched.h> +#include <debug.h> +#include <nuttx/kmalloc.h> +#include <nuttx/arch.h> +#include <nuttx/os_external.h> +#include "os_internal.h" +#include "sig_internal.h" +#include "mq_internal.h" + +/************************************************************ + * Definitions + ************************************************************/ + +/************************************************************ + * Private Type Declarations + ************************************************************/ + +/************************************************************ + * Global Variables + ************************************************************/ + +/************************************************************ + * Private Variables + ************************************************************/ + +/************************************************************ + * Private Functions + ************************************************************/ + +/************************************************************ + * Public Functions + ************************************************************/ + +/************************************************************ + * Function: mq_receive + * + * 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_receive will return an error. Otherwise, the + * select message is removed from the queue and copied to + * "msg." + * + * If the message queue is empty and O_NONBLOCK was not + * set, mq_receive() will block until a message is added + * to the message queue. 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. + * + * If the queue is empty and O_NONBLOCK is set, ERROR will + * be returned. + * + * 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. + * + * Return Value: + * Length of the selected message in bytes, otherwise -1 + * (ERROR). + * + * Assumptions: + * + ************************************************************/ + +int mq_receive(mqd_t mqdes, void *msg, size_t msglen, int *prio) +{ + _TCB *rtcb; + _TCB *btcb; + msgq_t *msgq; + mqmsg_t *curr; + uint32 saved_state; + ubyte rcvmsglen; + int ret = ERROR; + + /* Verify the input parameters */ + + sched_lock(); + if (msg && mqdes && (mqdes->oflags & O_RDOK) != 0 && + msglen >= (size_t)mqdes->msgq->maxmsgsize) + { + /* Get a pointer to the message queue */ + + msgq = mqdes->msgq; + + /* Several operations must be performed below: We must determine if + * a message is pending and, if not, wait for the message. Since + * messages can be sent from the interrupt level, there is a race + * condition that can only be eliminated by disabling interrupts! + */ + + saved_state = irqsave(); + + /* Get the message from the head of the queue */ + + while ((curr = (mqmsg_t*)sq_remfirst(&msgq->msglist)) == NULL) + { + /* Should we block until there the above condition has been + * satisfied? + */ + + if (!(mqdes->oflags & O_NONBLOCK)) + { + /* Block and try again */ + + rtcb = (_TCB*)g_readytorun.head; + rtcb->msgwaitq = msgq; + msgq->nwaitnotempty++; + up_block_task(rtcb, TSTATE_WAIT_MQNOTEMPTY); + } + else + { + break; + } + } + + /* If we got message, then decrement the number of messages in + * the queue while we are still in the critical section + */ + + if (curr) + { + msgq->nmsgs--; + } + irqrestore(saved_state); + + /* Check (again) if we got a message from the message queue*/ + + if (curr) + { + /* Get the length of the message (also the return value) */ + + ret = rcvmsglen = curr->msglen; + + /* Copy the message into the caller's buffer */ + + memcpy((void*)curr->mail, msg, rcvmsglen); + + /* Copy the message priority as well (if a buffer is provided) */ + + if (prio) + { + *prio = curr->priority; + } + + /* We are done with the message. Deallocate it now. */ + + mq_msgfree(curr); + + /* Check if any tasks are waiting for the MQ not full event. */ + + 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 = (_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); + } + } + } + + sched_unlock(); + return ret; +} |