Re: Regression: webcam freezing since Linux 6.15

[Bart Nagel <bart@tremby.net>]

At 2026-07-30 23:59:53 +0200, Michal Pecio wrote:
> On Thu, 30 Jul 2026 11:13:59 -0700, Bart Nagel wrote:
> > At 2026-07-30 13:08:14 +0200, Michal Pecio wrote:
> > > I'm slightly curious what exactly happens there (probably MSE after
> > > Short Packet on a single-TRB TD), and whether Missed Service Error
> > > may point at a Link TRB, because the current fix wouldn't handle
> > > that and the stream could still hang. So your failure rate may
> > > actually be reduced to 1/255 of what it was, but still not zero.
> > > 
> > > If possible, please boot the patched kernel again and run it for
> > > a little longer. If it fails, post dmesg starting from the "Miss
> > > service interval error" line which is followed by "All TDs skipped".
> > > 
> > > And while that is running, also collect another log:
> > > 
> > > cd /sys/kernel/tracing/
> > > echo 1 > events/xhci-hcd/xhci_handle_event/enable
> > > echo 1 > tracing_on
> > > grep -B5 Missed trace_pipe | tee /tmp/trace
> > > 
> > > This is supposed to log 6 lines for every Missed Service Error, so
> > > it will grow, but not terribly fast.  
> > 
> > Before I make a bad assumption and collect a useless log, please
> > confirm for me exactly which debugging I should enable. Just the two
> > you gave above, or also one or both of the ones I was using before:
> > 
> >     echo "func handle_tx_event +p" >/proc/dynamic_debug/control
> >     echo 0xff >/sys/module/uvcvideo/parameters/trace
> 
> Yes, please keep handle_tx_event, otherwise xhci_hcd debug messages
> won't show up. UVC trace is not that important.

OK. I ran it with your temporary patch for around 24 hours with heavy
system load and didn't get any freezes. The logs are large; please let
me know if there's anything I can grep for which might tell us that
the potential 1/255 chance of a freeze still being possible is ruled
out.

If you'd like me to run it longer I could, but I otherwise intend now
to switch over to your more formal patch. I will post a question in
that thread shortly.

--bart