panic: vm_page_astate_fcmpset: invalid head requeue request on RPI3

[bob prohaska]

While playing at compiling www/chromium using 
FreeBSD 13.0-CURRENT (GENERIC) #2 r356165: Mon Dec 30 09:59:03 PST 2019
the machine crashed, reporting 
 panic: vm_page_astate_fcmpset: invalid head requeue request for page 0xfffffd0031880490

cpuid = 2
time = 1577921727
KDB: stack backtrace:
db_trace_self() at db_trace_self_wrapper+0x28
	 pc = 0xffff000000735c5c  lr = 0xffff000000106814
	 sp = 0xffff0000521ec240  fp = 0xffff0000521ec450

db_trace_self_wrapper() at vpanic+0x18c
	 pc = 0xffff000000106814  lr = 0xffff000000408d90
	 sp = 0xffff0000521ec460  fp = 0xffff0000521ec510

vpanic() at panic+0x44
	 pc = 0xffff000000408d90  lr = 0xffff000000408b40
	 sp = 0xffff0000521ec520  fp = 0xffff0000521ec5a0

panic() at _vm_page_pqstate_commit_dequeue+0x340
	 pc = 0xffff000000408b40  lr = 0xffff0000006ed840
	 sp = 0xffff0000521ec5b0  fp = 0xffff0000521ec5f0

_vm_page_pqstate_commit_dequeue() at vm_page_pqstate_commit_dequeue+0xb8
	 pc = 0xffff0000006ed840  lr = 0xffff0000006e954c
	 sp = 0xffff0000521ec600  fp = 0xffff0000521ec640

vm_page_pqstate_commit_dequeue() at vm_page_pqstate_commit+0x50
	 pc = 0xffff0000006e954c  lr = 0xffff0000006e93ac
	 sp = 0xffff0000521ec650  fp = 0xffff0000521ec670

vm_page_pqstate_commit() at vm_pageout_laundry_worker+0x5e4
	 pc = 0xffff0000006e93ac  lr = 0xffff0000006f02c0
	 sp = 0xffff0000521ec680  fp = 0xffff0000521ec940

vm_pageout_laundry_worker() at fork_exit+0x7c
	 pc = 0xffff0000006f02c0  lr = 0xffff0000003c7fdc
	 sp = 0xffff0000521ec950  fp = 0xffff0000521ec980

fork_exit() at fork_trampoline+0x10
	 pc = 0xffff0000003c7fdc  lr = 0xffff00000075230c
	 sp = 0xffff0000521ec990  fp = 0x0000000000000000

KDB: enter: panic
[ thread pid 21 tid 100071 ]
Stopped at      0
db> bt
Tracing pid 21 tid 100071 td 0xfffffd0001078560
db_trace_self() at db_stack_trace+0xf8
         pc = 0xffff000000735c5c  lr = 0xffff000000103c58
         sp = 0xffff0000521ebe10  fp = 0xffff0000521ebe40

db_stack_trace() at db_command+0x228
         pc = 0xffff000000103c58  lr = 0xffff0000001038d0
         sp = 0xffff0000521ebe50  fp = 0xffff0000521ebf30

db_command() at db_command_loop+0x58
         pc = 0xffff0000001038d0  lr = 0xffff000000103678
         sp = 0xffff0000521ebf40  fp = 0xffff0000521ebf60

db_command_loop() at db_trap+0xf4
         pc = 0xffff000000103678  lr = 0xffff00000010697c
         sp = 0xffff0000521ebf70  fp = 0xffff0000521ec190

db_trap() at kdb_trap+0x1d8
         pc = 0xffff00000010697c  lr = 0xffff0000004510d0
         sp = 0xffff0000521ec1a0  fp = 0xffff0000521ec250
        
kdb_trap() at do_el1h_sync+0xf4
         pc = 0xffff0000004510d0  lr = 0xffff000000752588
         sp = 0xffff0000521ec260  fp = 0xffff0000521ec290

do_el1h_sync() at handle_el1h_sync+0x78
         pc = 0xffff000000752588  lr = 0xffff000000738078
         sp = 0xffff0000521ec2a0  fp = 0xffff0000521ec3b0

handle_el1h_sync() at kdb_enter+0x34
         pc = 0xffff000000738078  lr = 0xffff00000045071c
         sp = 0xffff0000521ec3c0  fp = 0xffff0000521ec450

kdb_enter() at vpanic+0x1a8
         pc = 0xffff00000045071c  lr = 0xffff000000408dac
         sp = 0xffff0000521ec460  fp = 0xffff0000521ec510

vpanic() at panic+0x44
         pc = 0xffff000000408dac  lr = 0xffff000000408b40
         sp = 0xffff0000521ec520  fp = 0xffff0000521ec5a0
        
panic() at _vm_page_pqstate_commit_dequeue+0x340
         pc = 0xffff000000408b40  lr = 0xffff0000006ed840
         sp = 0xffff0000521ec5b0  fp = 0xffff0000521ec5f0

_vm_page_pqstate_commit_dequeue() at vm_page_pqstate_commit_dequeue+0xb8
         pc = 0xffff0000006ed840  lr = 0xffff0000006e954c
         sp = 0xffff0000521ec600  fp = 0xffff0000521ec640

vm_page_pqstate_commit_dequeue() at vm_page_pqstate_commit+0x50
         pc = 0xffff0000006e954c  lr = 0xffff0000006e93ac
         sp = 0xffff0000521ec650  fp = 0xffff0000521ec670

vm_page_pqstate_commit() at vm_pageout_laundry_worker+0x5e4
         pc = 0xffff0000006e93ac  lr = 0xffff0000006f02c0
         sp = 0xffff0000521ec680  fp = 0xffff0000521ec940

vm_pageout_laundry_worker() at fork_exit+0x7c
         pc = 0xffff0000006f02c0  lr = 0xffff0000003c7fdc
         sp = 0xffff0000521ec950  fp = 0xffff0000521ec980
        
fork_exit() at fork_trampoline+0x10
         pc = 0xffff0000003c7fdc  lr = 0xffff00000075230c
         sp = 0xffff0000521ec990  fp = 0x0000000000000000

db> 

Thanks for reading, if there's anything to try please let me know.

bob prohaska