08f7152d9f
It takes about 10 cycles to obtain the task list according to the task status. In most cases, we know the task status, so we can directly add the task from the specified task list to reduce time consuming.
289 lines
8.1 KiB
C
289 lines
8.1 KiB
C
/****************************************************************************
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* sched/mqueue/msgrcv.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <assert.h>
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#include <nuttx/cancelpt.h>
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#include "sched/sched.h"
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#include "mqueue/msg.h"
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: msgrcv_wait
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****************************************************************************/
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static int msgrcv_wait(FAR struct msgq_s *msgq, FAR struct msgbuf_s **rcvmsg,
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long msgtyp, int msgflg)
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{
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FAR struct msgbuf_s *newmsg = NULL;
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FAR struct msgbuf_s *tmp;
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FAR struct tcb_s *rtcb;
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bool switch_needed;
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#ifdef CONFIG_CANCELLATION_POINTS
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/* msgrcv_wait() is not a cancellation point, but it may be called
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* from msgrcv() which are cancellation point.
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*/
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if (check_cancellation_point())
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{
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/* If there is a pending cancellation, then do not perform
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* the wait. Exit now with ECANCELED.
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*/
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return -ECANCELED;
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}
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#endif
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/* Get the message from the head of the queue */
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while (1)
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{
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list_for_every_entry(&msgq->msglist, tmp, struct msgbuf_s, node)
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{
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/* Unless MSG_COPY is specified in msgflg (see below), the msgtyp
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* argument specifies the type of message requested, as follows:
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*
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* 1. If msgtyp is 0, then the first message in the queue is read.
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*
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* 2. If msgtyp is greater than 0, then the first message in the
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* queue of type msgtyp is read, unless MSG_EXCEPT was
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* specified in msgflg, in which case the first message in the
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* queue of type not equal to msgtyp will be read.
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*
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* 3. If msgtyp is less than 0, then the first message in the
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* queue with the lowest type less than or equal to the
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* absolute value of msgtyp will be read.
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*/
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if (msgtyp < 0)
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{
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if (newmsg == NULL || newmsg->mtype > tmp->mtype)
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{
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newmsg = tmp;
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}
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}
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else if (msgtyp == 0 ||
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((msgflg & MSG_EXCEPT) != 0) == (tmp->mtype != msgtyp))
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{
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newmsg = tmp;
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break;
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}
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}
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if (newmsg)
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{
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list_delete(&newmsg->node);
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goto found;
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}
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if ((msgflg & IPC_NOWAIT) != 0)
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{
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return -EAGAIN;
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}
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/* The queue is empty! Should we block until there the above condition
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* has been satisfied?
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*/
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rtcb = this_task();
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rtcb->waitobj = msgq;
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msgq->cmn.nwaitnotempty++;
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/* Initialize the 'errcode" used to communication wake-up error
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* conditions.
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*/
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rtcb->errcode = OK;
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/* Make sure this is not the idle task, descheduling that
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* isn't going to end well.
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*/
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DEBUGASSERT(NULL != rtcb->flink);
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/* Remove the tcb task from the ready-to-run list. */
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switch_needed = nxsched_remove_readytorun(rtcb, true);
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/* Add the task to the specified blocked task list */
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rtcb->task_state = TSTATE_WAIT_MQNOTEMPTY;
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nxsched_add_prioritized(rtcb, MQ_WNELIST(msgq->cmn));
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/* Now, perform the context switch if one is needed */
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if (switch_needed)
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{
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up_block_task(rtcb);
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}
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/* When we resume at this point, either (1) the message queue
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* is no longer empty, or (2) the wait has been interrupted by
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* a signal. We can detect the latter case be examining the
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* errno value (should be either EINTR or ETIMEDOUT).
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*/
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if (rtcb->errcode != OK)
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{
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return -rtcb->errcode;
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}
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}
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found:
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msgq->nmsgs--;
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*rcvmsg = newmsg;
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return OK;
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: msgrcv
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*
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* Description:
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* The msgrcv() function reads a message from the message queue specified
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* by the msqid parameter and places it in the user-defined buffer
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* pointed to by the *msgp parameter.
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*
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* Input Parameters:
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* msqid - Message queue identifier
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* msgp - Pointer to a buffer in which the received message will be
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* stored
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* msgsz - Length of the data part of the buffer
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* msgtyp - Type of message to be received.
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* msgflg - Operations flags.
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*
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* Returned Value:
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* On success, msgrcv() returns the number of bytes actually copied
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* into the mtext array.
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* On failure, both functions return -1, and set errno to indicate
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* the error.
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*
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****************************************************************************/
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ssize_t msgrcv(int msqid, FAR void *msgp, size_t msgsz, long msgtyp,
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int msgflg)
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{
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FAR struct msgbuf_s *msg = NULL;
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FAR struct mymsg *buf = msgp;
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FAR struct msgq_s *msgq;
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FAR struct tcb_s *btcb;
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irqstate_t flags;
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int ret;
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if (msgp == NULL)
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{
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ret = -EFAULT;
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goto errout;
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}
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flags = enter_critical_section();
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msgq = nxmsg_lookup(msqid);
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if (msgq == NULL)
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{
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ret = -EINVAL;
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goto errout_with_critical;
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}
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if (msgsz < msgq->maxmsgsize &&
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((msgflg & MSG_NOERROR) == 0))
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{
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ret = -EMSGSIZE;
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goto errout_with_critical;
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}
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ret = msgrcv_wait(msgq, &msg, msgtyp, msgflg);
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if (ret < 0)
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{
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goto errout_with_critical;
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}
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ret = msgsz > msg->msize ? msg->msize : msgsz;
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buf->mtype = msg->mtype;
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memcpy(buf->mtext, msg->mtext, ret);
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list_add_tail(&g_msgfreelist, &msg->node);
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/* Check if any tasks are waiting for the MQ not full event. */
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if (msgq->cmn.nwaitnotfull > 0)
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{
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FAR struct tcb_s *rtcb = this_task();
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/* Find the highest priority task that is waiting for
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* this queue to be not-full in g_waitingformqnotfull list.
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* This must be performed in a critical section because
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* messages can be sent from interrupt handlers.
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*/
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btcb = (FAR struct tcb_s *)dq_remfirst(MQ_WNFLIST(msgq->cmn));
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/* If one was found, unblock it. NOTE: There is a race
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* condition here: the queue might be full again by the
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* time the task is unblocked
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*/
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DEBUGASSERT(btcb != NULL);
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if (WDOG_ISACTIVE(&btcb->waitdog))
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{
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wd_cancel(&btcb->waitdog);
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}
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msgq->cmn.nwaitnotfull--;
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/* Indicate that the wait is over. */
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btcb->waitobj = NULL;
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/* Add the task to ready-to-run task list and
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* perform the context switch if one is needed
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*/
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if (nxsched_add_readytorun(btcb))
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{
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up_unblock_task(btcb, rtcb);
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}
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}
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errout_with_critical:
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leave_critical_section(flags);
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errout:
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if (ret < 0)
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{
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set_errno(-ret);
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return ERROR;
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}
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return ret;
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}
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