kern/56557: Boot fails with DRM assertion failure

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         56557
>Category:       kern
>Synopsis:       Boot fails with DRM assertion failure
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Dec 19 19:35:01 +0000 2021
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date 2021.12.19.16.01.29
>Organization:
  
>Environment:
System: NetBSD
Architecture: i386
Machine: i386
>Description:

After today's DRM update, my Dell Latitude D400 i386 laptop testbed
panics on boot with the message

  [   7.2163355] panic: kernel diagnostic assertion "!ctx->wwx_acquire_done" failed: file "/tmp/build/2021.12.19.16.01.29-i386-laptop/src/sys/external/bsd/drm2/linux/linux_ww_mutex.c", line 555 ctx 0xc2715f44 done acquiring locks, can't acquire more

Console log:

  https://www.gson.org/netbsd/bugs/build/i386-laptop/2021/2021.12.19.16.01.29/test.log

Before the DRM update, the machine in case was already reporting DRM
errors on boot, but it did boot:

  https://www.gson.org/netbsd/bugs/build/i386-laptop/2021/2021.12.18.18.05.55/test.log

>How-To-Repeat:

Boot -current/i386 on a Dell Latitude D400.

>Fix: