Probably bug in condition::timed_wait()

20 Sep 2006

      Hi,

I'm porting custom library from UNIX to Windows and found that some 
piece of code work correctly on UNIX and some time segfaulting  on 
Windows. I think, that problem is on boost::condition::timed_wait() 
function. To be sure I write small test:

#include <stdexcept>
#include <iostream>

#include 

#include 

using namespace boost;
using namespace std;

class AsyncQueue {
public:
    AsyncQueue() : m_counter(0) {}

    void push()
    {
        mutex::scoped_lock lock(m_mutex);
        m_counter++;
        m_condition.notify_one();
    }

    void timed_pop(const xtime &time)
    {
        mutex::scoped_lock lock(m_mutex);

        if(m_counter) {
            m_counter--;
            return;
        }

        if(!m_condition.timed_wait(lock, time)) return;

        if(!m_counter) throw out_of_range("oops...");

        m_counter--;
    }

private:
    mutex m_mutex;
    condition m_condition;

    int m_counter;
};

static AsyncQueue queue;

static void start()
{
    for(;;) {
        queue.push();
        Sleep(100);
    }
}

int main(int argc, char **argv)
{
    thread thread(start);

    xtime time;

    for(;;) {
        xtime_get(&time, TIME_UTC);
        time.nsec += 10000;
        queue.timed_pop(time);
    }

    return 0;
}

AsyncQueue is a simple asynchronous queue container with two operations 
- push() and timed_pop(). Because this is test, AsyncQueue don't really 
collect something, but it's has variable (m_counter field) that count 
current number on elements in container. When push() called m_counter 
incremented and when timed_pop() "virtually" remove item from queue 
m_counter decremented.

In main() I create additional thread, which push data to queue. Data 
popped from queue in main thread by calling timed_pop(). But sometimes 
timed_pop throw out_of_range exception. If you look in code you can see 
that it's mean that condition::timed_wait() return true, but queue is empty!

I look to boost-users list and found e-mail's about similar problems 
from Eric Colleu, but decision wasn't found.

Two words about my environment. I use Visual Studio 2005, Windows XP SP2 
on VMWare 5.5.1. Boost version is 1.33.1.

Thanks for constructive answers.

Pavel Syomin

Peter Dimov

Pavel Syomin

Peter Dimov

Moshe Matitya

Pavel Syomin

tags

participants (3)