Bug 248732 - LOR on a recent -CURRENT between UFS and devfs
Summary: LOR on a recent -CURRENT between UFS and devfs
Status: Closed FIXED
Alias: None
Product: Base System
Classification: Unclassified
Component: kern (show other bugs)
Version: CURRENT
Hardware: Any Any
: --- Affects Many People
Assignee: freebsd-bugs (Nobody)
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2020-08-18 19:20 UTC by Gordon Bergling
Modified: 2021-11-02 18:25 UTC (History)
2 users (show)

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Description Gordon Bergling freebsd_committer freebsd_triage 2020-08-18 19:20:55 UTC 
On an ARM64 PRi4B I get the following LOR:

The system is mounting a NFS share very late, if this leads more towards solving this problem.

lock order reversal:
 1st 0xfffffd0061a35c10 ufs (ufs, lockmgr) @ /tank/nfs_public/tiny/src/sys/kern/vfs_mount.c:1008
 2nd 0xfffffd0061a3b450 devfs (devfs, lockmgr) @ /tank/nfs_public/tiny/src/sys/kern/vfs_mount.c:1019
lock order devfs -> ufs established at:
#0 0xffff00000040eeec at witness_lock_order_add+0xec
#1 0xffff00000040e4e0 at witness_checkorder+0x23c
#2 0xffff000000380ff8 at lockmgr_lock_flags+0x150
#3 0xffff0000005dea68 at ffs_lock+0x68
#4 0xffff0000006dc560 at VOP_LOCK1_APV+0x40
#5 0xffff00000048684c at VOP_LOCK1+0x2c
#6 0xffff000000485578 at _vn_lock+0x38
#7 0xffff00000046c54c at vfs_domount_first+0x440
#8 0xffff000000469d14 at vfs_domount+0x270
#9 0xffff000000469040 at vfs_donmount+0x6cc
#10 0xffff00000046bb1c at kernel_mount+0x54
#11 0xffff00000046e664 at parse_mount+0x270
#12 0xffff00000046d7b8 at vfs_mountroot_parse+0xf4
#13 0xffff00000046d2d4 at vfs_mountroot+0x25c
#14 0xffff000000349f7c at start_init+0x2c
#15 0xffff00000036e22c at fork_exit+0x80
lock order ufs -> devfs attempted at:
#0 0xffff00000040e954 at witness_checkorder+0x6b0
#1 0xffff0000003823e4 at lockmgr_xlock+0x50
#2 0xffff000000462294 at vop_lock+0x7c
#3 0xffff0000006dc560 at VOP_LOCK1_APV+0x40
#4 0xffff00000048684c at VOP_LOCK1+0x2c
#5 0xffff000000485578 at _vn_lock+0x38
#6 0xffff00000046c54c at vfs_domount_first+0x440
#7 0xffff000000469d14 at vfs_domount+0x270
#8 0xffff000000469040 at vfs_donmount+0x6cc
#9 0xffff000000468920 at sys_nmount+0x60
#10 0xffff0000006807f0 at syscallenter+0x2c8
#11 0xffff000000680170 at svc_handler+0x4c
#12 0xffff00000067ff80 at do_el0_sync+0xf0
#13 0xffff000000667224 at handle_el0_sync+0x90
Comment 1 Mark Johnston freebsd_committer freebsd_triage 2020-08-28 13:15:18 UTC 
I believe this is a known false positive.
Comment 2 Gordon Bergling freebsd_committer freebsd_triage 2021-01-15 14:56:51 UTC 
After some investigation, the LOR happens when a jail mounting it's devfs, or better said, if devfs is enabled in the jail configuration.