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Re: [ uvideo crashes 5.0_RC1 / i386]

On Sat, Jan 31, 2009 at 01:51:52PM +0000, Jeremy Morse wrote:
> Rafal Boni wrote:
> > So out of desperation I tried to feed /dev/video0 to 'mplayer', and
> > was rewarded with the machine crashing, see the picture below --
> >
> > 
> > Any ideas?  Known issue? Should I PR it?
> > --rafal
> According to Logitechs website this is a high-speed usb2 webcam, and
> from your dmesg uvideo is attaching at a full-speed usb1.1 host controller.
> What's _probably_ happening is uvideo allocating hundreds of xfers and
> feeding them to uhci, which internally limits itself to 128 xfers at a
> time, and that leads to some memory corruption. This has caused a panic
> for at least one person in the past [0].
> To confirm this, could you re-build the kernel with options DIAGNOSTIC
> enabled? If the above is correct, you should see a couple of
> "uhci_device_isoc_enter: overflow!" lines before it panics.

Adding DIAGNOSTIC to the kernel (and rebuilding from scratch), I see
a bunch of 'uhci_device_icoc_enter: overflow!' messages if I run 
mplayer as:

        $ mplayer /dev/video0

The interesting thing is it didn't crash (at least not for a few mins;
pre-DIAGNOSTIC it didn't last nearly that long), and I was able to kill
mplayer and repeat the experiment a few times without crashing.  I will
file the first (non-DIAGNOSTIC) crash as a new PR unless you already have
one open, Jeremy..

Interestingly enough, having noticed another email about a uvideo crash
on the list today (
31/msg000033.html), I ran mplayer as:

        $ mplayer -tv fps=25 tv://

and was actually rewarded with video (ok, the first time on the console;
I didn't know that mplayer did cheesy ASCII interpolation... scary!).  On
the second try I ran it from within X and while the video is broken up and
mplayer complains about 'frame too small' and 'select timeout's I do get
video output -- though it's broken up as one might expect if frames were
being read partially and/or chopped -- and everything runs without crashing.


  Time is an illusion; lunchtime, doubly so.     |/\/\|           Rafal Boni
                   -- Ford Prefect               |\/\/|

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