[linux-dvb] [BUG] changeset 9029 (http://linuxtv.org/hg/v4l-dvb/rev/aa3e5cc1d833)

Mauro Carvalho Chehab mchehab at infradead.org
Mon Feb 16 19:31:48 CET 2009


On Mon, 16 Feb 2009 08:19:06 -0800 (PST)
Trent Piepho <xyzzy at speakeasy.org> wrote:

> On Sun, 15 Feb 2009, Oliver Endriss wrote:
> > e9hack wrote:
> > > this change set is wrong. The affected functions cannot be called from an interrupt
> > > context, because they may process large buffers. In this case, interrupts are disabled for
> > > a long time. Functions, like dvb_dmx_swfilter_packets(), could be called only from a
> > > tasklet. This change set does hide some strong design bugs in dm1105.c and au0828-dvb.c.
> > >
> > > Please revert this change set and do fix the bugs in dm1105.c and au0828-dvb.c (and other
> > > files).
> >
> > @Mauro:
> >
> > This changeset _must_ be reverted! It breaks all kernels since 2.6.27
> > for applications which use DVB and require a low interrupt latency.
> >
> > It is a very bad idea to call the demuxer to process data buffers with
> > interrupts disabled!
> 
> I agree, this is bad.  The demuxer is far too much work to be done with
> IRQs off.  IMHO, even doing it under a spin-lock is excessive.  It should
> be a mutex.  Drivers should use a work-queue to feed the demuxer.

Hartmut, Oliver and Trent: Thanks for helping with this issue. I've just
reverted the changeset. We still need a fix at dm1105, au0828-dvb and maybe
other drivers that call the filtering routines inside IRQ's.


Cheers,
Mauro



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