[linux-dvb] Problems with APIC/LAPIC (was: Re: Problems with SMP (i.e. dualcore) system: dvb-ttpci: warning: timeout waiting in LoadBitmap)

Sven Mueller linux-dvb at incase.de
Mon Aug 6 22:12:41 CEST 2007

Oliver Endriss wrote on 05/08/2007 06:14:
> Sven Mueller wrote:
>> Oliver Endriss wrote on 01/08/2007 00:27:
>>> Sven Mueller wrote:
>>>> Hi.
>>>> I don't know which hardware interrupts those are mapped from/to and
>>>> currently don't know how to find out.
>>>> If you need any further data to give a helpful answer, don't hesitate to
>>>> ask.
>>> Which firmware are you using?
>> Most recent AFAICT (261f).
> Nope, the most recent firmware is
> http://linuxtv.org/downloads/firmware/dvb-ttpci-01.fw-2622

I tested that one as well, but I wasn't sure wether it was actually
newer, since the downloads I could find on the Technotrend pages only
had 261f IIRC.

>>> Does the VDR recover if you wait some time (1 or 2 minutes) before you
>>> press the next key?
>> Sometimes (if I interpret things correctly though, this is due to an
>> internal watchdog in VDR triggering a restart, which now, on my system,
>> includes module unload/reload due to my problems).
> With recent firmware VDR should recover _without_ emergency exit.

It might do, I currently don't have much time to do tests (and, to be
honest: not much inclination to do tests just to find out if and how the
system recovers after a failure).

>>> You might also try whether this driver improves things:
>>> http://linuxtv.org/hg/~endriss/v4l-dvb-av7110-refactoring/
>> Will take a look into that later once I find some time.
>> One think fixed the problem for me, for now though:
>> noapic nolapic
>> on the kernel commandline (grub).
> Are you sure that this did not disable SMP?

Hmm, /proc/cpuinfo reports two CPUs and I had two processes (just some
Perl processes with while loops counting up until a certain file was
created) for which top reported near 100% CPU usage. So I'm quite
certain it didn't disable SMP.

>> However the system runs stable in every other aspect, so it seems to me
>> that enabling apic/lapic does something which the dvb_ttpci driver
>> doesn't handle properly on SMP systems.
> There is no special handling for SMP or non-SMP systems.
> Of course there might be a bug which will only show up with SMP. :-(

Right, that is what I thought of first, too, but as said I'm almost 100%
sure I now have a stable system running with SMP (though without
APIC/LAPIC). So the bug (which I think is somewhere in dvb_ttpci) seems
to be triggered by some LAPIC or APIC specific code somewhere in the
kernel (i.e. not necessarily in the dvb_ttpci driver).


PS: No need to CC me, I'm subscribed.

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