fad41c80b3
This allow main thread to terminate without any error when each car thread has terminated. It's more accurate, because otherwise the attendant will wait forever and block the program.
94 lines
2.0 KiB
C++
94 lines
2.0 KiB
C++
#include <iostream>
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#include <chrono>
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#include <semaphore>
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#include <thread>
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#include <vector>
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#include <mutex>
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using namespace std;
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mutex cout_mutex;
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#define print(X) cout_mutex.lock(); cout << X << endl; cout_mutex.unlock();
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#define N 25
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// GLOBAL VARIABLES
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int carsWaiting = 0;
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mutex mutexCar;
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counting_semaphore carArrived(0);
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counting_semaphore bayFree(0);
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counting_semaphore carWashed(0);
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counting_semaphore washingDone(0);
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void car(size_t id)
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{
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// car arrives
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print("Car " << id << " arrives at the car wash");
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mutexCar.lock();
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if (carsWaiting == N) {
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mutexCar.unlock();
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print("Car " << id << " leaves due to no waiting space");
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return;
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}
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++carsWaiting;
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mutexCar.unlock();
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// rendezvous 1
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carArrived.release(); // signal X
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bayFree.acquire(); // wait Y
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// getCarWash
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print("Car " << id << " is being washed");
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this_thread::sleep_for(chrono::seconds(1));
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print("Car " << id << " is washed");
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// rendezvous 2
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carWashed.release(); // signal X'
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washingDone.acquire(); // wait Y'
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// car leaves
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mutexCar.lock();
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--carsWaiting;
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mutexCar.unlock();
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print("Car " << id << " leaves the car wash");
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}
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void attendant()
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{
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while (true) {
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// rendezvous 1
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carArrived.acquire(); // wait X
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bayFree.release(); // signal Y
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// washCar
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print("Attendant starts washing a car");
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this_thread::sleep_for(chrono::seconds(1));
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print("Attendant finishes washing");
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// rendezvous 2
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carWashed.acquire(); // wait X'
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washingDone.release(); // signal Y'
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}
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}
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int main()
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{
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print("Car wash opening with " << N << " waiting spaces");
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thread attendantThread(attendant);
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attendantThread.detach();
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vector<thread> cars {};
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for(size_t i = 0; i < N+1; ++i)
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{
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thread t(car, i);
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cars.push_back(std::move(t));
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}
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for (auto &car: cars) {
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car.join();
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}
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return 0;
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}
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