Bug 235513 - panic: dead bo 0xfffff8000a838b48
Summary: panic: dead bo 0xfffff8000a838b48
Status: New
Alias: None
Product: Base System
Classification: Unclassified
Component: kern (show other bugs)
Version: CURRENT
Hardware: Any Any
: --- Affects Only Me
Assignee: Jason A. Harmening
URL:
Keywords: stress2
Depends on:
Blocks:
 
Reported: 2019-02-05 08:12 UTC by Peter Holm
Modified: 2019-04-14 08:20 UTC (History)
2 users (show)

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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.