Estoy mirando el problema del productor/consumidor con threads en c+11. Pues bien, el siguiente código me da un problema con helgrind detecta una condicion de carrera y debuggeando un poco creo que el problema esta en la funcion consumer pero no estoy seguro y no se como resolverlo.
Código [Seleccionar]
#include <iostream>
#include <sstream>
#include <vector>
#include <stack>
#include <thread>
#include <mutex>
#include <atomic>
#include <condition_variable>
#include <chrono>
using namespace std;
// print function for "thread safe" printing using a stringstream
void print(ostream& s) { cout << s.rdbuf(); cout.flush(); s.clear(); }
const int num_producers = 5;
const int num_consumers = 10;
const int producer_delay_to_produce = 10; // in miliseconds
const int consumer_delay_to_consume = 30; // in miliseconds
const int consumer_max_wait_time = 200; // in miliseconds - max time that a consumer can wait for a product to be produced.
const int max_production = 10; // When producers has produced this quantity they will stop to produce
const int max_products = 10; // Maximum number of products that can be stored
atomic<int> num_producers_working(0); // When there's no producer working the consumers will stop, and the program will stop.
stack<int> products; // The products stack, here we will store our products
mutex xmutex; // Our mutex, without this mutex our program will cry
condition_variable is_not_full; // to indicate that our stack is not full between the thread operations
condition_variable is_not_empty; // to indicate that our stack is not empty between the thread operations
void produce(int producer_id)
{
unique_lock<mutex> lock(xmutex);
int product;
is_not_full.wait(lock, [] { return products.size() != max_products; });
product = products.size();
products.push(product);
print(stringstream() << "Producer " << producer_id << " produced " << product << "\n");
is_not_empty.notify_one();
}
// Consume function, consumer_id will consume a product
void consume(int consumer_id)
{
unique_lock<mutex> lock(xmutex);
int product;
if(is_not_empty.wait_for(lock, chrono::milliseconds(consumer_max_wait_time),
[] { return products.size() > 0; }))
{
product = products.top();
products.pop();
print(stringstream() << "Consumer " << consumer_id << " consumed " << product << "\n");
is_not_full.notify_one();
}
}
void producer(int id)
{
++num_producers_working;
for(int i = 0; i < max_production; ++i)
{
produce(id);
this_thread::sleep_for(chrono::milliseconds(producer_delay_to_produce));
}
print(stringstream() << "Producer " << id << " has exited\n");
--num_producers_working;
}
void consumer(int id)
{
// Wait until there is any producer working
while(num_producers_working == 0) this_thread::yield();
while(num_producers_working != 0 || products.size() > 0)
{
consume(id);
this_thread::sleep_for(chrono::milliseconds(consumer_delay_to_consume));
}
print(stringstream() << "Consumer " << id << " has exited\n");
}
int main()
{
vector<thread> producers_and_consumers;
// Create producers
for(int i = 0; i < num_producers; ++i)
producers_and_consumers.push_back(thread(producer, i));
// Create consumers
for(int i = 0; i < num_consumers; ++i)
producers_and_consumers.push_back(thread(consumer, i));
// Wait for consumers and producers to finish
for(auto& t : producers_and_consumers)
t.join();
}
