syscons: Hitting an assertion in init_scp while booting

[Rumko]

While trying to boot the machine with latest -master, it panics with "panic:
assertion: (&tty_token)->t_ref && (&tty_token)->t_ref->tr_owner == curthread
in init_scp".

I can see the following through the serial console:
vga0: <Generic ISA VGA> [attached!] at port 0x3c0-0x3df iomem 0xa0000-0xbffff
on isa1
kbdc: DIAGNOSE status:0055
kbdc: TEST_KBD_PORT status:0000
kbdc: DIAGNOSE status:0055
kbdc: TEST_KBD_PORT status:0000
sc0.isa1.isab1.pci0.pcib0.legacy0.nexus0.root0
sc0: <System console> [tentative] at flags 0x100 on isa1
panic: assertion: (&tty_token)->t_ref && (&tty_token)->t_ref->tr_owner ==
curthread in init_scp
mp_lock = 00000000; cpuid = 0
Trace beginning at frame 0xc069f734
panic(ffffffff) at panic+0x174
panic(c0402788,c042d960,c03fe514,1c8787,c048cc30) at panic+0x174
init_scp(14c,c0481d40,802,d7a930a0,d80de4c0) at init_scp+0x4d
alloc_scp(0,0,18,0,c3b45818) at alloc_scp+0x28
scinit(c,0,3,9,c) at scinit+0x25b
sc_attach_unit(0,100,c3b45818,c3b45818,c3b45818) at sc_attach_unit+0xa3
scattach(c3b45818,c0488bb4,d7958848,c044e434,d7944d48) at scattach+0x1d
device_doattach(c3b454f8,0,c3a61070,c3b02618,c3b01920) at device_doattach+0x27
device_probe_and_attach(c3b45818) at device_probe_and_attach+0x2fe
isa_probe_children(c3b454f8) at isa_probe_children+0xc5
configure(0,fffffff,69cc00,6aa000,6aa000) at configure+0x17
mi_startup(69c000,0,0,0,0) at mi_startup+0x92
begin() at begin+0x42
boot() called on cpu#0
Uptime: 14s
atkbdc0: wake_prep disabled wake for \_SB_.PCI0.LPC0.KBC0 (S5)
unknown: wake_prep disabled wake for \_SB_.PCI0.LPC0.MSE0 (S5)
unknown: wake_prep disabled wake for \_SB_.PCI0.USB1 (S5)
unknown: wake_prep disabled wake for \_SB_.PCI0.USB2 (S5)
unknown: wake_prep disabled wake for \_SB_.PCI0.USB3 (S5)
unknown: wake_prep disabled wake for \_SB_.PCI0.USB4 (S5)
unknown: wake_prep disabled wake for \_SB_.PCI0.EUSB (S5)
Automatic reboot in 15 seconds - press a key on the console to abort
-- 
Regards,
Rumko