With CVS of Nov 10 18:40 GMT (and tty.c,v 1.201), I got

panic: kernel diagnostic assertion "mutex_owned(&tty_lock)" failed: file "../../../../kern/tty.c", line 2204
breakpoint(c04c9194,c046d1a1,c049054b,c0490512,89c) at netbsd:breakpoint+0x1
__kernassert(c046d1a1,c0490512,89c,c049054b,3) at netbsd:__kernassert+0x39
ttwakeup(ca2e8dc8,ca2e8e00,c0f0ea63,c0f0ea00,c114ae54) at netbsd:ttwakeup+0x85
pppasyncctlp(c114ac00,0,2b,c0f0ea38,c04dc760) at netbsd:pppasyncctlp+0x3e
pppintr(c114ac00,c1038000,7ff,0,0) at netbsd:pppintr+0x2bb
softintr_dispatch(1,ca2dbc0c,f0c23ca5,uvm_fault(0xc04f43c0, 0xcaad7000, 1) -> 0xe

I am no longer near to that computer, but just saw something similar
while running tip on another one (same mesage, no pppd)

Cheers,

Patrick