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From: Michael Tuexen <tuexen@freebsd.org>
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Date: Wed, 29 Jul 2009 18:26:11 +0200
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Cc: Bruce Simpson <bms@incunabulum.net>
Subject: mld_mtx lock order reversal
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Dear all,

when doing a
ifconfig gif0 down
ifconfig gif0 -tunnel
ifconfig gif0 destroy
I got a the following message on the last command.
Is this a false positive?

Best regards
Michael

--- syscall (304, FreeBSD ELF64, kldload), rip = 0x8006923ac, rsp =  
0x7fffffffed38, rbp = 0 ---
lock order reversal:
  1st 0xffffff0002995bc8 if_afdata (if_afdata) @ net/if.c:830
  2nd 0xffffffff80de59c0 mld_mtx (mld_mtx) @ netinet6/mld6.c:570
KDB: stack backtrace:
db_trace_self_wrapper() at db_trace_self_wrapper+0x2a
_witness_debugger() at _witness_debugger+0x2e
witness_checkorder() at witness_checkorder+0x81e
_mtx_lock_flags() at _mtx_lock_flags+0x78
mld_domifdetach() at mld_domifdetach+0x24
in6_domifdetach() at in6_domifdetach+0x11
if_detach() at if_detach+0x6ed
gif_clone_destroy() at gif_clone_destroy+0xda
ifc_simple_destroy() at ifc_simple_destroy+0x2a
if_clone_destroyif() at if_clone_destroyif+0xc0
ifioctl() at ifioctl+0x6f5
kern_ioctl() at kern_ioctl+0xc5
ioctl() at ioctl+0xfd
syscall() at syscall+0x1af
Xfast_syscall() at Xfast_syscall+0xe1