[linux-dvb] Re: ARM crashes, what can I do to help?

[Holger Waechtler <holger@convergence.de>]

Hi,

Jaakko Hyvätti wrote:
>   My experiences with the new av7110 firmware are that if you do not touch
> the vdr OSD at all or only minimally, it does not crash when doing
> simultaneous recording and playback, or when watching the same channel as
> recording (transfer thread used).
> 
>   I other words, ARM crashes in less than a minute if I do something
> that displays something on OSD.
> 
>   Someone suspected the MPEG decoder might have wild pointers/buffer
> overruns on corrupted streams.  I have a lot of errors on some channels
> and occassionally on all channels, so this would explain a lot.  Maybe the
> wild pointers corrupt the firmware memory in such areas that when OSD
> functions are called it might crash?  I also have a lot of strange things
> happening with the OSD.  Sometimes some lines disappear, some garbage
> pixels appear all over the screen etc.  This would strongly point to
> memory corruption.
> 
> So to crash ARM, I guess I need:
> 
> - a corrupted MPEG stream,
> - a playback or transfer thread simultaneously with recording and
> - OSD activity.
> 
>   This would explain why the new firmware works for some people.  They
> have clean MPEG streams.
> 
>   Now I tried to disable OSD (Use vdr DEBUG_OSD), and got no ARM crash.
> Instead the machine locked up after quite a long while.  I could not
> reproduce this, but could the crashing arm take PCI bus with it, or does
> this kind of a lockup have to be always the drivers fault?

it's pretty unlikely that a crashed ARM directly locks up the host 
machine. I would expect some of the ARM communication functions might 
deadlock. Can you please press alt-sysrq-t and then pipe the output of 
dmesg through ksymoops to get an idea where it hangs?


>   These latest tests I did with vdr-1.1.13 but all versions have behaved
> the same.  I am using the new head revision of the driver cvs (with DVB-C
> fixed again of course) and tested also siemens_dvb-0.9.4-2002-06-23.patch
> as distributed on vdr site.
> 
>   What I am trying to point out here is that I think fixing the firmware
> is the only way to fix these problems.  Now the source and tools to
> compile are available only to few people in the project.  How can I help?
> I can crash the ARM quickly and reliably.  Should I insert some more
> debugging to the driver and see if there is a pattern to which calls cause
> the crash?  Please just tell me what to do.

All we can do is to try to work around these bugs and hope that Ralph 
will fix them one day...

Holger



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