watchdogs

[Mark Atkinson]

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On 02/20/2013 11:36, Eugene M. Zheganin wrote:
> 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 ?

I just want to /metoo that I have 32bit/i386 box running zfs, pf and
- -current that is hardlocking randomly (usually has an uptime for a few
days to a couple weeks).   SW_WATCHDOG won't fire when it locks so it
must be locking pretty fast.

I just noticed that ichwd will load on this box, so I'll try that
instead, but now I'm wondering if the SW_WATCHDOG kernel will
interfere or rather if watchdogd is smart enough to handle both?

This box used to occasionally panic on the ZFS stack panic so I did
the KSTACK_PAGES=4 change to the kernel and now it just hardlocks.
I'm not saying they are related.

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