kern/54401: panic on shutdown - [xhcixfer] pool busy: still out: 1

[venture37%geeklan.co.uk@localhost]

>Number:         54401
>Category:       kern
>Synopsis:       panic on shutdown - [xhcixfer] pool busy: still out: 1
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jul 23 10:30:00 +0000 2019
>Originator:     Sevan Janiyan
>Release:        HEAD
>Organization:
>Environment:
NetBSD 8.99.51 (GENERIC) #0: Thu Jul 18 20:10:46 UTC 2019  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64
>Description:
panic: kernel diagnostic assertion "(pp->pr_nout == 0)" failed: file "/usr/src/sys/kern/subr_pool.c", line 888 pool_destroy: [xhcixfer] pool busy: still out: 1

vpanic()
stge_eeprom_wait.isra.4()
pool_destroy()
pool_cache_destroy()
xhci_detach()
xhci_pci_detach()
config_detach()
config_detach_all()
cpu_reboot()
sys_reboot()
syscall()
--- syscall (number 208) ---

>How-To-Repeat:
Issue halt -p
>Fix: