[linux-dvb] Re: Problems with TechnoTrend dec2000-t USB

[Johannes Stezenbach <js@convergence.de>]

Holger Waechtler wrote:
> Alex Woods wrote:
> >
> >>...
> >>
> >>From all this, the commands I give is:
> >>
> >># dvbtune -c 0 -f 650000 -qam 16 -cr 2_3 -gi 8 -n 900
> >># ifconfig dvb0_0 192.168.0.1 netmask 255.255.255.0
> >># ifconfig dvb0_0 up promisc
> >>(panic described before, "kernel bug in sched.c:564")
> >>
> >>I'd be very pleased if anybody could tell me if I'm doing something wrong.
> >
> >
> >If you get a kernel panic, then it's not your fault, but a bug in the 
> >code.  If you don't require a dvb net interface, try playing with tzap 
> >from the linux-dvb pre-release tarball.  Hopefully I'll get a chance to 
> >look at fixing the problem soon.
> 
> The problem is that the software demux feeds the network interface in 
> interrupt context, the network code is then trying to sleep and that's 
> not allowed. Thus the BUG() call.
> 
> The USB DVB drivers need to use tasklets like the PCI DVB drivers too, 
> thenafter you can use the DVB network interface, too.

I don't think so. For one, tasklets can't sleep either. And the network
code is explicitely written to pass network packets from interrupt
context to the network layer (because that's how network interface
hardware usually works).

IIRC there is a race condition at ifconfig time, and a solution was described
by on of the Metzlers here on this list some months ago. Maybe it's even
fixed in their driver.

Johannes


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