Waitable Timer Lock Up

[vezprog]

My application currently runs 6-8 threads concurrently depending on how it is configured. Each thread uses a custom waitable timer class that I wrote to get a 20 mS loop timing. Furthermore, Each thread lives for the life of the application.

The issue I am having is that some of the threads lock up on the WaitForSingleObject() call on the windows waitable timer interface after X amount of time. X varies.

Here is my Precision Timer class:

// precision timer class
class PrecisionTimer
{
public:
    PrecisionTimer() : mMilli(-1), mHandle(NULL){}
    virtual ~PrecisionTimer(){ close(); }

    // free the handle
    void close()
    {
        // free up any existing handles / timers
        if (mHandle != NULL){
            CancelWaitableTimer(mHandle);
            CloseHandle(mHandle);
            mHandle = NULL;
        }
    }
     
    // start the timer 
    bool start(const unsigned int& milli)
    {
        // create the timer
        if (!create())
            return false;

        // set the internal variables
        mMilli = milli; // mS time
        // get the system time
        SYSTEMTIME cTime;        // System time structure
        GetSystemTime(&cTime);    // Curren time
        cTime.wMilliseconds += mMilli;        // Wait 3 sec

        // get the file time expected by waitable timer
        FILETIME fileTime;
        SystemTimeToFileTime(&cTime, &fileTime);
        // set the waitable timer
        return SetWaitableTimer(mHandle, reinterpret_cast<LARGE_INTEGER>(&fileTime), mMilli, NULL, NULL, 0);
    }

    // stop the timer
    void stop()
    {
        // check if the handle exists...
        if (mHandle)
            CancelWaitableTimer(mHandle);    // Stop timer
    }
 
    // wait for timer to expire
    bool wait()
    {
        // wait for the timer to fire...
        if (mHandle){
            switch (WaitForSingleObject(mHandle, mMilli)){
                case WAIT_ABANDONED:
                case WAIT_OBJECT_0:
                case WAIT_TIMEOUT: return true;
                case WAIT_FAILED: return false;
            }
        }
        else
            return false;
    }

private:
    bool create()
    {
        // close any existing timers
        close();

        // create the timer handle
        mHandle = CreateWaitableTimer(NULL, FALSE, NULL);
        return mHandle != NULL ? true : false;
    }

    unsigned int mMilli;

protected:
    HANDLE mHandle;
};

Here is an example of the how I am using the timer:

void MyThread::run()
{
    // set the timer settings
    PrecisionTimer taskTimer;
    taskTimer.start(20); // 20mS
    while (true){
        // do process
        taskTimer.wait();
    }
}

Are their any limitations I am missing with the waitable timer or to many handles from separate threads? Or maybe an operating system limitation?

NOTE: The thread that it happens the most on (lock up) is doing processing from an RS232 port. I am using Window 8 64-bit with MSVC2010

[Computergeek01]

You can call it a personal preference if you want but I have always hated timers. Are you sure that there isn't another synchronization method you could use? My first thought is that depending on a number of things it isn't entirely unreasonable to suspect that more then 20 mS have passed between the creation of your timer and it's call to "WaitForSingleObject()" so the object may already be signaled by that point in which case the behavior of that wait function is undefined. What are the threads these timers get attached to doing?