Date: Mon, 25 Feb 2013 00:04:41 -0800 From: Alfred Perlstein <bright@mu.org> To: Mark Atkinson <atkin901@gmail.com> Cc: freebsd-stable@freebsd.org Subject: Re: watchdogs Message-ID: <512B1B19.3000207@mu.org> In-Reply-To: <kg87el$iip$1@ger.gmane.org> References: <512525C1.1070502@norma.perm.ru> <kg87el$iip$1@ger.gmane.org>
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On 2/22/13 8:47 AM, Mark Atkinson wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > 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? watchdog(4) will arm all watchdogs. watchdogd uses watchdog(4) so yes, both watchdogs (SW_WATCHDOG & ichwd) should be armed. > > 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. Interesting. What is the default for KSTACK_PAGES? Btw, from all I've heard less than 4GB ram + ZFS == you're gonna have a bad time. There are supposedly some ways to make it somewhat reliable by disabling certain features, but I don't know the tricks off hand. -Alfred
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