port-sparc/56788: Rump kernel panic: kernel diagnostic assertion "old == LOCK_LOCKED" failed

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

>Number:         56788
>Category:       port-sparc
>Synopsis:       Rump kernel panic: kernel diagnostic assertion "old == LOCK_LOCKED" failed
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    port-sparc-maintainer
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Apr 10 11:35:00 +0000 2022
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current of 2011 to present
>Organization:
  
>Environment:
System: NetBSD
Architecture: sparc
Machine: sparc
>Description:

On the TNF sparc testbed, various networking tests randomly fail with
a rump kernel panic:

  [   1.3700050] panic: kernel diagnostic assertion "old == LOCK_LOCKED" failed: file "/tmp/build/2022.04.05.05.04.04-sparc/src/sys/rump/net/lib/libshmif/if_shmem.c", line 157

Logs from the most recent occurrences:

  http://releng.netbsd.org/b5reports/sparc/2022/2022.03.25.23.16.04/test.html#net_icmp_t_ping_ping_of_death

  http://releng.netbsd.org/b5reports/sparc/2022/2022.03.29.22.29.29/test.html#net_icmp_t_ping_pingsize

  http://releng.netbsd.org/b5reports/sparc/2022/2022.04.05.05.04.04/test.html#net_bpfilter_t_bpfilter_bpfiltermchain

This is a long-standing issue, going back at least to 2011.  I have
not seen it on architectures other than sparc.

>How-To-Repeat:

>Fix: