On 2/20/13 11:36 AM, 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 ?
Yes all your assumptions are correct.
There is an 'enhanced watchdog' branch that I am working on that offers
a "pre-watchdog timeout panic". However since this is done via the
software you may not get your pre-timeout panic and only have a reboot.
Later revisions may include facilities for generating NMI to trigger
panic/logs and the followed by a hard reset by external hardware.
Perhaps ichwd offers ability to send NMI? Let me check sources.
-Alfred
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