kern/56705: wapbl lockdebug panic during tcpdump run

[Hauke Fath <hauke%Espresso.Rhein-Neckar.DE@localhost>]

>Number:         56705
>Category:       kern
>Synopsis:       wapbl lockdebug panic during tcpdump run
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Feb 12 17:10:00 +0000 2022
>Originator:     Hauke Fath
>Release:        NetBSD 9.99.93
>Organization:
Falling Raindrops
>Environment:
	
	
System: NetBSD pizza 9.99.93 NetBSD 9.99.93 (BLACKBOX-$Revision: 1.85 $) #5: Fri Feb 11 21:11:10 CET 2022 hauke@pizza:/var/obj/netbsd-build-objects/developer/amd64/sys/arch/amd64/compile/BLACKBOX amd64
Architecture: x86_64
Machine: amd64
>Description:

	I am attempting to debug a client machine's hang during tcp
	transfers (here: an ftp session) by running tcpdump on the
	target (ftp server) machine. Unfortunately, the tcpdump
	frequently aborts with a 'no permission' error, and every few
	attempts the machine panics with a lockdebug error in a wapbl
	write

	<ftp://ftp.causeuse.org/pub/NetBSD/tcpdump-panic.gif>

	The USB console keyboard is dead at that point, and the
	machine swaps to a raidframe mirror, which cannot be dumped to.

	Strangely enough, the directory that tcpdump writes the pcap
	file to is on zfs, and so is the directory ftp'ed to.


	
>How-To-Repeat:

	tcpdump an incoming ftp transfer on the ftp server side. Watch
	the machine panic on (roughly) every fifth attempt.

	
>Fix:
	Yes, please.

	

>Unformatted: