Re: time drift in camonitor timestamps

[Eric Norum <eric@norum.ca>]

It's the epicsEventWaitWithTimeout().  This allows the pause to be interrupted early in the case of IOC shutdown.


static void periodicTask(void *arg)
{
    periodic_scan_list *ppsl = (periodic_scan_list *)arg;

    epicsTimeStamp nextScan, now;
    double delay;

    taskwdInsert(0, NULL, NULL);
    epicsEventSignal(startStopEvent);

    epicsTimeGetCurrent(&nextScan);
    while (ppsl->scanCtl != ctlExit) {
        if (ppsl->scanCtl == ctlRun) scanList(&ppsl->scan_list);
        nextScan += ppsl->period;
        epicsTimeGetCurrent(&now);
        delay = epicsTimeDiffInSeconds(&nextScan, &now);
        if (delay <= 0.0) {
            ppsl->overrunCount++;
            delay = 0.01;
            epicsTimeGetCurrent(&nextScan);
        }
        epicsEventWaitWithTimeout(ppsl->loopEvent, delay);      <<<<===== Here's where the magic happens.
    }

    taskwdRemove(0);
    epicsEventSignal(startStopEvent);
}


On Jan 9, 2013, at 10:35 AM, Jack Smith <jacksmithvent2009@gmail.com> wrote:

> Wow, amazing! It seems Eric fixed the problem which has been known for
> 2.5 years.
> 
> A little bit off-topic question: when I look through periodicTask( )
> which is the thread created by spawnPeriodic() for individual
> corresponding scanning period, I don't see any kind of 'timer' to
> trigger scanList(&ppsl->scan_list). So, my question is  how scanList(
> ) is periodically called in periodicTask( ) and where the 'timer'
> thing is?
> 
> Thanks,
> 
> Jack
> 

-- 
Eric Norum
eric@norum.ca