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POHow to access info about a thread throughout a program
 

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  1. POHow to access info about a thread throughout a program
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    <p>Question 1: I am trying to name each thread so it can be used throughout the program but am receiving errors like "request for member 'fid' in 'planes[t]' which is of non-class type 'pthread_t'. It is referring to use of planes[t].tid or use of planes[t].startState. I'm not sure how else to get/save these values for each individual thread.</p> <p>Question 2: once I have a thread's startState, how can I send the thread to a takeoff() function (series of switch states and printfs).</p> <p>Question 3: What should be passed into the StartState function? I'm trying to have each thread remember its start state so that later in the code I can have a flight be "landing" or "taking off." </p> <p>Here is the relevant code: <strong>Updated 10/06 at 22:37</strong></p> <pre><code>#include &lt;pthread.h&gt; #include &lt;stdio.h&gt; #include &lt;cstdlib&gt; #include &lt;iostream&gt; #include &lt;queue&gt; #include &lt;unistd.h&gt; #include &lt;algorithm&gt; #include &lt;time.h&gt; #include &lt;ctime&gt; #define NUM_THREADS 3 //3 flights using std::queue; using std::vector; pthread_mutex_t runway1lock; pthread_mutex_t runway2lock; bool run1occupied; bool run2occupied; struct flight_data{ //each plane has these characteristics //void *FlightID; long fid; int startState; // if start=1 ==&gt; taking off ::: if start=2 ==&gt; landing int flyTime; //fly == randomly generated time (order) of takeoff/land }; struct flight_data flightinfo[NUM_THREADS]; void *FlightID(void *flightid){ struct flight_data *my_flights; my_flights = (struct flight_data*)flightid; int taskid; taskid = my_flights-&gt;fid; // long fid; // fid = (long)flightid; // printf("Flight #%1d\n", tid); pthread_exit(NULL); } void Start(struct flight_data my_flights){ my_flights = (struct flight_data)my_flights; int startState; srand(time(0)); my_flights.startState = rand() % 2+1; std::string startstring; if(my_flights.startState == 1){ startstring = "Taking off"; } if(my_flights.startState == 2){ startstring = "Landing"; } for(int i = 1; i&lt;NUM_THREADS+1; i++){ std::cout &lt;&lt; "Start state for Flight # " &lt;&lt; i &lt;&lt; " is " &lt;&lt; startstring &lt;&lt; std::endl; } } void takeoff(struct flight_data my_flights){ my_flights = (struct flight_data)my_flights; for(int i = 1; i&lt;NUM_THREADS+1; i++){ int state = my_flights.startState; switch(state){ case 1:{ //G (GATE) std::cout &lt;&lt; "Flight # " &lt;&lt; flightinfo[i].fid &lt;&lt; " is listed as waiting at the gate." &lt;&lt; std::endl; std::cout &lt;&lt; "Flight # " &lt;&lt; flightinfo[i].fid &lt;&lt; "'s position in queue for runway: " &lt;&lt; flightinfo[i].flyTime &lt;&lt; std::endl; sleep(3); state = 2; break; } case 2: { //Q (queue) -- sets order for use of runway queue&lt;pthread_t&gt; queue; vector&lt;int&gt; flightTimes; int soonestFlightTime = 10; flightTimes.push_back(flightinfo[i].flyTime); //put all flight times into a vector called flightTimes std::sort(flightTimes.begin(), flightTimes.end()); //sort the vector of flightTimes low to high std::reverse(flightTimes.begin(), flightTimes.end()); //flips vector -- high(front) to low(back) while(!flightTimes.empty()){ if (flightinfo[i].flyTime == flightTimes.back()){ //if a thread has the soonest flight time queue.push(i); //then put the flight in the runway queue flightTimes.pop_back(); //pop off the soonest flight time } } while(!queue.empty()){ if(flightinfo[i].fid == queue.front()){ state = 3; queue.pop(); sleep(3); } } break; } case 3: { //CLR (clearance for runway) std::cout &lt;&lt; "Flight # " &lt;&lt; flightinfo[i].fid &lt;&lt; " has clearance to move to the runway." &lt;&lt; std::endl; //will go in order of queue if(run1occupied){ sleep(3); } // else if(collide){ // state = 7; // } else{ state = 4; } break; } case 4: { //RTO (runway takeoff) pthread_mutex_lock(&amp;runway1lock); run1occupied = true; std::cout &lt;&lt; "Flight # " &lt;&lt; flightinfo[i].fid &lt;&lt; " is taking off. Runway occupied. Stand by." &lt;&lt; std::endl; sleep(3); pthread_mutex_unlock(&amp;runway1lock); run1occupied = false; state = 5; break; } case 5: { //CZ (cruise) std::cout &lt;&lt; "Flight # " &lt;&lt; flightinfo[i].fid &lt;&lt; " is reaching proper altitude and cruising toward destination." &lt;&lt; std::endl; sleep(3); // if(!collide){ state = 6; // } // else{ // state = 7; //collision!!! // } break; } case 6: { //RMV (remove from monitoring list) std::cout &lt;&lt; "Flight # " &lt;&lt; flightinfo[i].fid &lt;&lt; " has been removed from the monitoring list." &lt;&lt; std::endl; break; } case 7:{ //COLL (collision) std::cout &lt;&lt; "Collision in the air. There were many casualties." &lt;&lt; std::endl; break; } } } } void landing(struct flight_data my_flights){ my_flights = (struct flight_data)my_flights; for (int i = 0; i&lt;NUM_THREADS; i++){ int state = my_flights.startState; switch(state){ case 1:{ //ENTR (enter monitoring list) state = 2; break; } case 2:{ //Q (queue) //if not the first thing in the queue then state = 4; //otherwise state = 3; } case 3:{ //RWL (runway land) state = 5; break; } case 4:{ //HVR (hover) //if first in queue then state = 3; //otherwise stay here //if collision state = 7; } case 5:{ //CLR (clearance to move to gate) //if collision state = 7 //otherwise state = 6; } case 6:{ //G (gate) } case 7:{ //COLL (collision) } } } } /* bool collision(){ bool collide; //random if(){ collide = true; } else{ collide = false; } return collide; }*/ int main(int argc, char *argv[]){ pthread_t flights[NUM_THREADS]; //pthread_t keeps a thread ID after the thread is created with pthread_create() //it's like an index on a vector of threads int *taskids[NUM_THREADS]; int rc; long t; for (t=1; t&lt;=NUM_THREADS; t++){ //loop creates threads(flights) printf("In main: Creating flight %1d\n", t); flightinfo[t].fid= t; rc = pthread_create(&amp;flights[t], NULL, FlightID, (void *)&amp;flights[t]); if (rc){ printf("ERROR: return code from pthread_create() is %d\n", rc); return (-1); } printf("Created flight %1d\n", t); // Start(flightinfo[t]); flightinfo[t].startState = rand() % 2+1; std::cout &lt;&lt; flightinfo[t].startState &lt;&lt; std::endl; if((flightinfo[t].startState)==1){ std::cout &lt;&lt; "Flight # " &lt;&lt; flightinfo[t].fid &lt;&lt; " is listed with start state as " &lt;&lt; flightinfo[t].startState &lt;&lt; std::endl; takeoff(flightinfo[t]); //go to takeoff function and go through switch case } if((flightinfo[t].startState)==2){ std::cout &lt;&lt; "Flight # " &lt;&lt; flightinfo[t].fid &lt;&lt; " is listed with start state as " &lt;&lt; flightinfo[t].startState &lt;&lt; std::endl; landing(flightinfo[t]); //go to landing function and go through switch case } } pthread_exit(NULL); } </code></pre>
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    1. USRichard Chambers
    1. USAnna
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    1. COI suggest that you start by cleaning up this source a bit. First change would be to replace use of void with actual type names in argument lists rather than taking a void and then casting to the actual type. The compiler is your friend and your first level of defense so use it as much as possible for static error checking.
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      1. POHow to access info about a thread throughout a program
      1. USRichard Chambers
    2. CO@Richard: You *can't*. Type erasure is needed for the context variable passed to `pthread_create` and thence to the thread procedure. Well, I am confused because it looks like he has two functions designed as thread procedures, but only one is used that way.
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      1. POHow to access info about a thread throughout a program
      1. USBen Voigt
    3. CO@BenVoigt, StartState().
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      1. POHow to access info about a thread throughout a program
      1. USRichard Chambers
 

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