On Thu, Aug 11, 2011 at 9:19 PM, nico <nicolas.guillot@gmail.com> wrote:

Hello.

I wrote a simple program that use the condition_variable class to synchronize 2 threads, as explained here :
http://www.boost.org/doc/libs/1_47_0/doc/html/thread/synchronization.html#thread.synchronization.condvar_ref

When I fork a a given point (see example below), the wait of the condition_variable never ends.
(I tried the code on ubuntu and fedora, and with boost 1.41 and boost 1.44).

I can't explain why, and how to solve (or workaround).

If I fork at the beginning of the program, it's ok.

Here follows the code,
the output is:

going to wait
End of processus of pid [5092]

and the code is:

#include <iostream>
#include "boost/thread.hpp"
#include "boost/bind.hpp"
#include <signal.h>
#include <cstdlib>

using namespace std;

boost::mutex mut;
boost::condition_variable cond_var;
bool cond;

void MyThread()
{
    sleep(3);
    {
        boost::lock_guard<boost::mutex> lock(mut);
        cond = true;
    }
    cond_var.notify_one();
}

int main()
{
    pid_t pid;

    cond = false;

    boost::thread(boost::bind(MyThread));

    pid = fork();
    if (pid == 0)
    {
        boost::unique_lock<boost::mutex> lock(mut);

        while (cond == false)
        {
            cout << "going to wait" << endl;
            cond_var.wait(lock);
            cout << "awake" << endl;
        }

        cout << "continue" << endl;
    }
    else
    {
        sleep(10);
    }

    cout << "End of processus of pid [" << pid << "]" << endl;
}

thanks for help!

Nicolas.