kern/56194: xhci panic: kernel diagnostic assertion "xs->xs_xr[dci] == NULL" failed

[nia%pkgsrc.org@localhost]

>Number:         56194
>Category:       kern
>Synopsis:       xhci panic: kernel diagnostic assertion "xs->xs_xr[dci] == NULL" failed
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri May 21 15:15:00 +0000 2021
>Originator:     nia
>Release:        current
>Organization:
The NetBSD Foundation
>Environment:
NetBSD amnesia 9.99.82 NetBSD 9.99.82 (NIAAMD64) #2: Tue May 18 12:32:39 CEST 2021  nia@amnesia:/src/obj/sys/arch/amd64/compile/NIAAMD64 amd64
>Description:
The system gradually locked up over a few seconds while using uaudio
for output, then eventually panicked:

System panicked: kernel diagnostic assertion "xs->xs_xr[dci] == NULL" failed: file "/src/src/sys/dev/usb/xhci.c", line 1669

This is an older uaudio device that worked before Isochronous Pipe
support was introduced:

$ dmesg | grep uaudio
[   756.135042] uaudio0 at uhub1 port 2 configuration 1 interface 0
[   756.135042] uaudio0: C-Media Electronics Inc. (0x0d8c) USB Audio Device (0x0014), rev 1.10/1.00, addr 2
[   756.135042] uaudio0: audio rev 1.00
[   756.135042] audio1 at uaudio0: playback, capture, full duplex, independent
$ audiocfg list
0: [*] audio1 @ uaudio0: USB audio
       playback: 2ch, 48000Hz
       record:   1ch, 48000Hz
       (P-) slinear_le 16/16, 2ch, { 48000, 44100 }
       (-R) slinear_le 16/16, 1ch, { 48000, 44100 }


Unfortunately the core dump is invalid and most tools dump themselves
while trying to read it - kernel memory corruption?
>How-To-Repeat:

>Fix: