Bug 235513

Summary: panic: dead bo 0xfffff8000a838b48
Product: Base System Reporter: Peter Holm <pho>
Component: kernAssignee: Jason A. Harmening <jah>
Status: New ---    
Severity: Affects Only Me CC: cem, jah
Priority: --- Keywords: stress2
Version: CURRENT   
Hardware: Any   
OS: Any   

Description Peter Holm freebsd_committer freebsd_triage 2019-02-05 08:12:26 UTC
A "umount -f /dev" will trigger this.
https://people.freebsd.org/~pho/stress/log/devfs4.txt
Comment 1 commit-hook freebsd_committer freebsd_triage 2019-02-05 08:15:26 UTC
A commit references this bug:

Author: pho
Date: Tue Feb  5 08:15:20 UTC 2019
New revision: 343768
URL: https://svnweb.freebsd.org/changeset/base/343768

Log:
  PR:		235513
  Sponsored by:	Dell EMC Isilon

Changes:
  user/pho/stress2/misc/devfs4.sh
Comment 2 Mark Linimon freebsd_committer freebsd_triage 2019-02-07 19:28:22 UTC
Peter added a test-case but that doesn't fix the underlying problem.
Comment 3 Jason A. Harmening freebsd_committer freebsd_triage 2019-04-14 08:20:48 UTC
It looks like we already claim to support forcible devfs unmount, mostly for jails it seems.  This particular panic is from a longstanding KASSERT, so at least the case of INVARIANTS + devfs forced unmount hasn't been well tested.
I'll poke at this and see if I can tease out some useful fix.  Probably not, given the foot-shooting nature of the problem, but at least I might learn something about the buffer cache.