[linux-dvb] Re: NEWSTRUCT bug report

[Holger Waechtler <holger@convergence.de>]

Philip Armstrong wrote:
> On Tue, Jul 30, 2002 at 10:23:26AM +0200, Holger Waechtler wrote:
> 
>>Philip Armstrong wrote:
>>
>>>With the latest CVS checkout of the NEWSTRUCT dvb drivers, after
>>>inserting the modules with "make insmod", the kernel thread "kdvb-fe"
>>>eats around 40% of CPU until I run dvbstream to stream some data from
>>>the card (I have a Hauppage NovaT terrestrial DVB card).
>>
>>This is normal when the CPU is running idle and the card has not tuned. 
>>It tries then to find a channel by scanning a wider frequency range. 
>>When either a signal is found the load of the thread should fall near zero.
>>
>>When CPU load rises the relative load of the thread should get much lower.
> 
> 
> Oh right. I did wonder if it might be something like that, but it
> keeps doing so for at least several minutes. How long would you expect
> it to take?

(Forever until it finds a valid DVB signal;)

The old driver stopped after some seconds, but this would cause problems 
for DVB-T where the signal can be lost for some seconds, especially when 
you use a mobile receiver.

Even in the DVB-S or DVB-C case the new behaviour makes sense, imagine a 
situation where the signal is lost for a while, there the frontend 
thread has to check regulary the tuner status in order to reset the 
Demux when there is a valid MPEG stream again.

Don't worry about the CPU load, 40% sounds a lot, but it's the idle case
when your CPU does not has to do anything useful anyway. Just try to give
some load on your box, you will see that the kdvb-fe thread will use 
less than 5%-10% then.


>>>Also, 10% of the time, the kernel panics when I try to run
>>>dvbstream. I could try and send along the panic data if it would be
>>>any help...
>>
>>Could you please send me the ksymoops output? Create it by piping the 
>>output from dmesg into ksymoops.
> 
> 
> I'll try, but we're taking a total machine lockup here -- the panic
> happens inside an interrupt handler and the machine halts on the
> spot. I'll try and remember to copy down the data by hand next time it
> happens.

Do you use a SMP kernel?

Holger



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