Message queue mqmonitor msgqcreatemaxmsgs maxmsglen

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/*** message queue ***/ mqMonitor = msgQCreate(MAX_MSGS, MAX_MSG_LEN, MAG_Q_PRIORITY); /* spawn tasks */ for (i=0;i<NT;i++) tids[i]=taskSpawn("myTask",150,0,20000,myTask,0,0,0,0,0,0,0,0,0,0); taskSpawn("tMonitor",100,0,20000,tMonitor,0,0,0,0,0,0,0,0,0,0); /* critical region, protected by semCount semaphore */ semTake(semCount, WAIT_FOREVER); /* try to take semaphore */ /* send operation code and tid */ sprintf(msgbuf,"%d 0", tid); msgQSend(mqMonitor,msgbuf,MAX_MSG_LEN,WAIT_FOREVER); /* send operation code and tid to ackonwledge deactivation */ sprintf(msgbuf,"%d 1", tid); msgQSend(mqMonitor,msgbuf,MAX_MSG_LEN,WAIT_FOREVER); semGive(semCount); /* execute critical section */
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void tMonitor (void) { int ActiveTasks[NT]; /* active tasks table */ int atptr; /* pointer to ActiveTasks table */ int i,code,tid; char msgbuf[MAX_MSG_LEN]; /* Initialize pointer */ atptr = 0; while(TRUE) { /* Wait for a request */ msgQReceive(mqMonitor,msgbuf,MAX_MSG_LEN,WAIT_FOREVER); sscanf(msgbuf, "%d %d", &code, &tid); if(code == 0) { /* task activated */ ActiveTasks[atptr] = tid; /* write task ID */ atptr++; } if(code == 1) { /* task deactivated */ /* find task’s entry in ActiveTasks table */ i = 0; while(ActiveTasks[i] != tid) i++; /* reorganize table */ if(atptr > 1) ActiveTasks[i] = ActiveTasks[atptr-1]; /* fill empty slot */ atptr--; /* update pointer */ } } }
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