Bad link elm 0xea9cba58 next->prev != elm

[Rumko <rumcic@xxxxxxxxx>]

With fairly recent master managed to produce the aforementioned panic, but have
no idea how or if it is repeatable. The dump is available at
leaf:~rumko/crash/bad_elm .

#0  _get_mycpu (di=0xc0535740) at ./machine/thread.h:83
#1  md_dumpsys (di=0xc0535740)
    at /usr/src/sys/platform/pc32/i386/dump_machdep.c:264
#2  0xc01e5d06 in dumpsys () at /usr/src/sys/kern/kern_shutdown.c:893
#3  0xc01e62c6 in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:388
#4  0xc01e6591 in panic (fmt=0xc047be44 "Bad link elm %p next->prev != elm")
    at /usr/src/sys/kern/kern_shutdown.c:799
#5  0xc01fbcb2 in softclock_handler (arg=0xc0544cb4)
    at /usr/src/sys/kern/kern_timeout.c:292
#6  0xc01ef464 in lwkt_deschedule_self (td=Cannot access memory at address 0x8
)
    at /usr/src/sys/kern/lwkt_thread.c:276
-- 
Please do not CC me, since I already receive everything from these MLs.

Regards,
Rumko