[linux-dvb] USB driver dmxdev crash on disconnection

Mark Watson linuxtv at foft.fsnet.co.uk
Wed Mar 22 22:14:00 CET 2006

On Sunday 19 March 2006 19:42, Mark Watson wrote:
> First a bit of background. About a year and a half ago I built myself a PVR
> using a Cypress FX2 to feed an mpeg TS from a digibox. This has been
> working great except the FX2 disconnects every few weeks (possibly heat
> related, I've just fitted a heatsink...). I'm finally trying to get to the
> bottom of why it crashes when it disconnects, with the help of kgdb. I can
> generally reproduce this crash by unplugging with vdr is running.
> My driver source is available at:
> http://www.scrameta.net/skympeg/dvb_skympeg.c (Feeds a whole transponder
> from an already configured FX2, filters a bit and pumps it into the kernel
> dvb demux)
> http://www.scrameta.net/skympeg/dvb_skympeg_fe.c (Just a stub for fake
> tuning to allow vdr to work)
> In dvb_skympeg.c my cleanup code, called on usb disconnect, does something
> like:
>         dev->dvb_demux.dmx.close(&dev->dvb_demux.dmx);
>         dev->dvb_demux.dmx.remove_frontend(&dev->dvb_demux.dmx,
> &dev->fe_hw); dev->dvb_demux.dmx.remove_frontend(&dev->dvb_demux.dmx,
> &dev->fe_mem); err("dvb_demux...");
>         dvb_dmxdev_release(&dev->dmxdev);
>         dvb_dmx_release(&dev->dvb_demux);
>         err("dvb_dmx_release");
>         if (dev->dvb_frontend) dvb_unregister_frontend(dev->dvb_frontend);
>         dev->dvb_frontend = 0;
>         err("dvb_unregister_frontend");
>         dvb_unregister_adapter(&dev->adapter);
>         err("dvb_unregister_adapter");
> The problem occurs after it has logged "dvb_dmx_release". The crash is in
> dmxdev.c:983 (in official) in dvb_demux_poll, as called by vdr.
> Now I can see why dmxdevfilter is invalid, since its been freed, but I'm
> not sure how to avoid this since I already called dvb_dmxdev_release. Do I
> need to check no-one is using the device before calling dvb_dmxdev_release?
> I do have an open count on my device (though I think thats for USB?), but
> no-one has it open. Sorry, not got much experience with device drivers on
> linux...
> Hope someone can help.
> Thanks,
> Mark
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> linux-dvb at linuxtv.org
> http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb

Please help! Do I need to provide more information? I only really want to know 
how I should be using the dvb_dmx_release. Presumably I need to check it is 
not being used before calling, but can't work out what. 



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