NetBSD xen dom0 kernel panic

[Frank <netbsd%searchy.net@localhost>]

A few times my test NetBSD server running NetBSD 5.0_RC2 (amd64) 
suddenly crashed. (every 2-3 days)

At the moment of the crash dmesg is:

panic: lock error
fatal breakpoint trap in supervisor mode
trap type 1 code 0 rip ffffffff804f374d cs e030 rflags 246 cr2 
ffffa00029343000
 cpl 6 rsp ffffa00028e4e278

A backtrace:

b> bt
breakpoint() at netbsd:breakpoint+0x5
panic() at netbsd:panic+0x242
lockdebug_abort() at netbsd:lockdebug_abort+0x42
mutex_vector_enter() at netbsd:mutex_vector_enter+0x104
pool_get() at netbsd:pool_get+0x45
pf_alloc_state_key() at netbsd:pf_alloc_state_key+0x27
pf_test_rule() at netbsd:pf_test_rule+0xc48
pf_test() at netbsd:pf_test+0xc3a
pfil4_wrapper() at netbsd:pfil4_wrapper+0x57
pfil_run_hooks() at netbsd:pfil_run_hooks+0xa0
bridge_ipf() at netbsd:bridge_ipf+0x239
pfil_run_hooks() at netbsd:pfil_run_hooks+0xa0
bridge_forward() at netbsd:bridge_forward+0xbd
bridge_input() at netbsd:bridge_input+0x14b
ether_input() at netbsd:ether_input+0x123
wm_intr() at netbsd:wm_intr+0x3c0
evtchn_do_event() at netbsd:evtchn_do_event+0xbe
call_evtchn_do_event() at netbsd:call_evtchn_do_event+0xd
hypervisor_callback() at netbsd:hypervisor_callback+0xa3
pf_purge_expired_states() at netbsd:pf_purge_expired_states+0x6f
pf_purge_thread() at netbsd:pf_purge_thread+0x5d


It doesn't seem completely related to anything else found in the 
mailinglist and in gnats.