KQUEUE/TTY related panic

Robert Watson rwatson at freebsd.org
Sun Sep 5 07:56:39 PDT 2004

On Sun, 5 Sep 2004, Maxim Maximov wrote:

> 	Just got a panic when dropped into DDB by Ctrl-Alt-Esc, issued
> 'show witness', pressed ScrLk, pressed PgUp ten times, then PgDn. Then
> released cursor by pressing ScrLk again. 

This is pretty much identical to the panic Jan Srzednicki reported,
wherein the syscons code under DDB calls into the TTY code (and really
shouldn't).  The low level polled console I/O routines are not supposed to
mess with schedulers, etc, etc.  CC'ing Doug White since he expressed some
interest in all this :-).

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert at fledge.watson.org      Principal Research Scientist, McAfee Research

> db> panic: blockable sleep lock (sleep mutex) tty @ 
> /usr/src/sys/kern/kern_event.c:1450
> cpuid = 0
> boot() called on cpu#0
> Uptime: 2m22s
> 	Machine freezes completely here. Keys didn't work. Reset helped.
> 	Tried exactly the same actions after reboot - exactly same effect.
> 	Machine is SMP, HTT, WITNESS enabled, today's HEAD.
> 	Dmesg is at http://mcsi.pp.ru/dmesg.boot
> -- 
> Maxim Maximov
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