watchdogs

[Eugene M. Zheganin]

Hi.

I have a bunch of FreeBSDs that hangs (and I really want to do something 
to fight this). May be it's the zfs or may be it's the pf (I also have a 
bunch of really stable ones, so it's hard to isolate and tell). Since 
9.x hang more often I suppose it's pf. I use ichwd.ko and watchdogd to 
reboot a machine when it hangs.  It works pretty well; I'm also working 
on a various WITNESS/INVARIANTS stuff and I'm trying to report it to 
gnats, but obviously it would be much nicer if the system would panic 
and leave some debuggable core after a hang (so far I don't have any, so 
I can only guess). I've read about software watchdog in kernel and I 
doesn'y quite understand: it's said that kernel software watchdog is 
able to panic when a deadlock occurs. Can this be achieved with ichwd ? 
Another one: as far as I understand ichwd reboots my machine on a 
hardware level, right ? So am I right saying that software watchdog can 
be, in theory, also deadlocked, thus, being kinda less reliable solution ?

Thanks.
Eugene.