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

Trent Piepho xyzzy at speakeasy.org
Mon Feb 16 17:19:06 CET 2009

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.

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