Jan: I think Gary has a good point here.
Another angle you should consider is something I've seen here repeatedly over time, having nothing to do with the software: power. External USB devices that are not USB-powered of course rely on their own power supply. Cheap wall-wart power adapters simply do NOT have the resilience of a PC power supply when it comes to dirty power. A nearby A/C compressor cycling on/off can glitch the power enough to crash an externally-wall-wart-powered USB device while PC internal power supplies usually have enough internal energy storage (i.e. capacitors) to ride out an event like that. I've *personally witnessed* this sort of thing in the past and there have been repeated reports of people with randomly crashing USB devices that magically fix themselves when their power supply is moved behind, say, a UPS or sometimes just a good surge protector (depending on the severity of the power issue). Your report mentions all 4 tuners crashing at once, which admittedly might be more likely a kernel USB stack bug. Note that the pvrusb2 driver instances itself once for every device you have connected. Since the driver instances generally operate independantly of one another, a driver misbehavior should not be able to cause simultaneous failure of all tuners at once. The fact that a system reboot does not clear the problem is another factor that suggests the foul-up is in the tuners themselves, though the trigger could still be the kernel USB stack. Since you have 4 tuners, you have a unique opportunity to try an experiment: Put just 2 of the tuners behind a UPS. Wait for the next failure. Do all four tuners fail at once again or just two? If only 2 fail now then that's almost a smoking gun clue indicating bad power. If you still have all 4 failing at once then I'd put my money on Gary's theory: a kernel USB stack bug. Another idea - if you have a portable USB hard drive, plug it in as well and run a repeated massive tar command to generate large amounts of I/O. When you next get a failure, does the hard drive survive while the tuners still fail? If the hard drive fails too, then you've just exonerated the entire V4L subsystem and I'd then be looking really hard at the USB stack. Hope that helps. -Mike On Wed, 21 Mar 2012, Jan Ceuleers wrote: > On 21/03/12 17:09, Gary Buhrmaster wrote: > > <conjecture> > > Understood, and thanks for your insights. > > > Almost certainly a kernel usb issue. The 1900s and the > > APC device are likely victims, not the cause. These types > > of bug reports (the 'clear tt' ones) with usb devices have a > > tendency to reoccur on some irregular basis as the usb > > subsystem in the kernel gets improved. Usually the > > problem is patched in the next kernel rev (because others > > have reported it), although sometimes you have to do the > > git bisect to find the patch that was "special" to get it fixed. > > Indeed my thoughts align with yours: the tuners are significant USB traffic > generators which are probably more likely than other devices to expose > weaknesses in the kernel USB subsystem. But I did google the kernel log > messages without success (probably because they are so terse). > > I recently upgraded from Ubuntu 10.10 to 11.04, and I had this problem under > 10.10 as well. So the problem is not restricted to the 2.6.38 kernel in 11.04. > > But I will try a more recent kernel as well before taking it to linux-usb if I > still need to. > > Thanks, Jan > _______________________________________________ > pvrusb2 mailing list > [email protected] > http://www.isely.net/cgi-bin/mailman/listinfo/pvrusb2 > -- Mike Isely isely @ isely (dot) net PGP: 03 54 43 4D 75 E5 CC 92 71 16 01 E2 B5 F5 C1 E8 _______________________________________________ pvrusb2 mailing list [email protected] http://www.isely.net/cgi-bin/mailman/listinfo/pvrusb2
