Date: Wed, 20 Feb 2013 11:41:17 -0800 From: Alfred Perlstein <bright@mu.org> To: "Eugene M. Zheganin" <emz@norma.perm.ru> Cc: freebsd-stable@freebsd.org Subject: Re: watchdogs Message-ID: <512526DD.1080707@mu.org> In-Reply-To: <512525C1.1070502@norma.perm.ru> References: <512525C1.1070502@norma.perm.ru>
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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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