kern/138332: ifconfig tun0 destroy causes LOR on 8.0-BETA3

Richard Tector richard at
Sun Aug 30 09:00:09 UTC 2009

>Number:         138332
>Category:       kern
>Synopsis:       ifconfig tun0 destroy causes LOR on 8.0-BETA3
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun Aug 30 09:00:08 UTC 2009
>Originator:     Richard Tector
>Release:        FreeBSD 8.0-BETA3 amd64
FreeBSD 8.0-BETA3 FreeBSD 8.0-BETA3 #17: Sat Aug 29 13:46:30 BST 2009     richard at  amd64
Issuing ifconfig tun0 destroy after stopping PPP causes a lock order reversal as follows:

tun0: link state changed to DOWN
lock order reversal:
 1st 0xffffff00037b4bc8 if_afdata (if_afdata) @ /usr/src/sys/net/if.c:912
 2nd 0xffffffff80a42200 mld_mtx (mld_mtx) @ /usr/src/sys/netinet6/mld6.c:569
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
_witness_debugger() at _witness_debugger+0x2e
witness_checkorder() at witness_checkorder+0x80b
_mtx_lock_flags() at _mtx_lock_flags+0x71
mld_domifdetach() at mld_domifdetach+0x24
in6_domifdetach() at in6_domifdetach+0x11
if_detach() at if_detach+0x792
tun_destroy() at tun_destroy+0x70
ifc_simple_destroy() at ifc_simple_destroy+0x2a
if_clone_destroyif() at if_clone_destroyif+0xc0
ifioctl() at ifioctl+0x6f4
kern_ioctl() at kern_ioctl+0xc3
ioctl() at ioctl+0xfc
syscall() at syscall+0x1b2
Xfast_syscall() at Xfast_syscall+0xe1
--- syscall (54, FreeBSD ELF64, ioctl), rip = 0x800a7bbbc, rsp = 0x7fffffffe238, rbp = 0x51cf28 ---
/etc/rc.d/ppp stop
ifconfig tun0 destroy


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