Re: Regression: webcam freezing since Linux 6.15

[Michal Pecio <michal.pecio@gmail.com>]

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.