[mythtv] more on dvb record failure (race condition in signalmonitor.cpp?)

[Mark Weaver]

Daniel Kristjansson wrote:
> On Mon, 2005-08-22 at 17:18 +0100, Mark Weaver wrote:
> 
>>Mark Weaver wrote:
>>
>>>I am also having trouble with DVB (livetv|recording) -- sometimes 
>>>getting the PMT timeout.  I have tried latest SVN but the backend seems 
>>>very unstable for me.  I've done a little debugging, so far I think I 
>>>have found a race condition in signalmonitor.cpp:
>>
It appears that the SignalMonitor class is reused (sometimes without an 
intervening call to Stop).  On the next run, exit=true therefore the 
thread just quits immediately, and Start() hangs waiting for running to 
become true (which it misses).  I tested this by running mythtv-setup 
and got a hang scanning channels.

void SignalMonitor::Stop()
{
     VERBOSE(VB_CHANNEL, QString("SignalMonitor::Stop(%1) -- 
begin").arg((unsign\
ed int)this));
     {
         QMutexLocker locker(&startStopLock);
         if (running)
         {
             exit = true;
             pthread_join(monitor_thread, NULL);
+           exit = false;
         }
     }

Setting exit=false again after pthread_join and inside the mutex looks 
correct to me if the class is to be reused (and solves that problem; 
scanning now completes), although I am unable to get a lock on any channels.

I am currently getting:

DVB#0 ERROR - Getting Frontend tuning parameters failed. (22) Invalid 
argument

So I'll look into that one next.