kern/55254: iwm panics under LCOKDEBUG after some time

[coypu%sdf.org@localhost]

>Number:         55254
>Category:       kern
>Synopsis:       iwm panics under LCOKDEBUG after some time
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon May 11 16:50:00 +0000 2020
>Originator:     coypu
>Release:        NetBSD 9.99.59
>Organization:
>Environment:
"pretending it's netbsd-10"
NetBSD planets 10.99.59 NetBSD 10.99.59 (GENERIC) #0: Mon May  4 23:02:45 IDT 2020  fly@planets:/home/fly/obj2/sys/arch/amd64/compile/GENERIC amd64
>Description:
[  4302.729814] panic: LOCKDEBUG: Mutex error: mi_switch,709: spin lock held
[  4302.729814] cpu10: Begin traceback...
[  4302.729814] vpanic() at netbsd:vpanic+0x178
[  4302.729814] snprintf() at netbsd:snprintf
[  4302.729814] lockdebug_more() at netbsd:lockdebug_more
[  4302.729814] mi_switch() at netbsd:mi_switch+0x179
[  4302.729814] sleepq_block() at netbsd:sleepq_block+0x17b
[  4302.729814] iwm_firmware_load_sect() at netbsd:iwm_firmware_load_sect+0x1c9
[  4302.729814] iwm_load_cpu_sections_7000() at netbsd:iwm_load_cpu_sections_7000+0x68
[  4302.729814] iwm_load_ucode_wait_alive() at netbsd:iwm_load_ucode_wait_alive+0x648
[  4302.729814] iwm_init_hw() at netbsd:iwm_init_hw+0xb3
[  4302.729814] iwm_init() at netbsd:iwm_init+0x3e
[  4302.729814] ifmedia_change() at netbsd:ifmedia_change+0x48
[  4302.729814] ifmedia_ioctl() at netbsd:ifmedia_ioctl+0x12c
[  4302.729814] ieee80211_ioctl() at netbsd:ieee80211_ioctl+0x398
[  4302.729814] iwm_ioctl() at netbsd:iwm_ioctl+0x169
[  4302.729814] doifioctl() at netbsd:doifioctl+0x990
[  4302.729814] sys_ioctl() at netbsd:sys_ioctl+0x59c
[  4302.729814] syscall() at netbsd:syscall+0x2ae
[  4302.729814] --- syscall (number 54) ---
[  4302.729814] 725912f8187a:
[  4302.729814] cpu10: End traceback...

>How-To-Repeat:

>Fix: