c++ - Conditional Variable doesn't wake up -

i have build pizzeria in c++ school project. in order have use thread , condvar. i'm doing condvar:

class condvar {   pthread_cond_t m_cond_var;   mutex _mut; public:   condvar()   {     _mut.init();     pthread_cond_init(&m_cond_var, null);   }   ~condvar()   {     pthread_cond_destroy(&m_cond_var);   }   void wait()   {     _mut.lock();     pthread_cond_wait(&m_cond_var, _mut.getmutex());     _mut.unlock();   }   void signal()   {     pthread_cond_signal(&m_cond_var);   }   void broadcast()   {     pthread_cond_broadcast(&m_cond_var);   } }; 

the constructor of kitchen:

kitchen::kitchen(int nb_cooks, float mult, int time_ing):_nb_cooks(nb_cooks), _mult(mult), _time_ing(time_ing) {   int   = 0;   _pipe = new pipeclass();   _fork = new fork();   if (_fork->isson())     {       _pipe->setson(true);       _run = true;       _cond = new condvar();       _stock.push_back(new mushrooms(5));        cook_mutex.init();       ingr_mutex.init();       while (i < _nb_cooks)         {           _cooks.push_back(new cook(mult, _pizzalist, *_cond, cook_mutex));           i++;         }       _thread = new thread(this);       run();     }   else     _pipe->setson(false); }   

i build pizza:

void    kitchen::dopizza() {   pizzagenerator        gen;   std::string   order;   apizza        *pizza;   std::vector<aingredient *>pizzaingr;   bool  check;    std::cout << "i pizza" << std::endl;   order = _pipe->getline();   pizza = gen.createforkitchen(order);   pizzaingr = pizza->getingredients();   if ((check = checkingredients(pizzaingr)) == false)     _pipe->write("ko");   else if (checkcooks() + _pizzalist.size() <= (unsigned int)(2 * _nb_cooks))     {       removeingredientsfromstock(pizzaingr);       _pizzalist.push_back(pizza);       std::cout << "je rentre dedans" << std::endl;       _cond->signal();       _pipe->write("ok");     } } 

and run of cook:

void    *cook::run() {   while (!_stop)     {       if (_pizzalist.size() != 0)         std::cout << "i can cook" << std::endl;       if (!_stop)         _cond.wait();     }   return null; } 

but condvar doesn't act.

this:

_mut.lock(); pthread_cond_wait(&m_cond_var, _mut.getmutex()); _mut.unlock(); 

fundamentally misunderstands how pthreads condition variables work. mutex argument pthread_cond_wait() isn't there embuggerance: condition variable must paired condition on shared state (often called predicate), , mutex passed should mutex protects shared state.

in other words, should use pthread_cond_wait() this:

pthread_mutex_lock(&mutex); /* ... */ while (!condition)     pthread_cond_wait(&cond, &mutex);  /* 'condition' true, , mutex held.  operation here  * depends upon 'condition' being true. */  pthread_mutex_unlock(&mutex); 

in case, looks condition cooks wait might "there @ least 1 pizza waiting cooked, or stop flag has been set". cooks need call code along these lines:

pizzalist_mutex.lock();  {     while (_pizzalist.size() == 0 && !stop)         pthread_cond_wait(&cond, pizzalist_mutex.getmutex());      if (_pizzalist.size() != 0)     {         /* remove pizza pizza list */         pizzalist_mutex.unlock();         /* cook pizza */         pizzalist_mutex.lock();     } } while (!stop);  pizzalist_mutex.unlock(); 

...where pizzalist_mutex mutex used protect pizzalist , global stop.

it perhaps make sense implement "wait pizza pizza list" method of pizza list object itself.