On Thu, 12 Jun 2008 18:43:40 -0300
Christian Robottom Reis <kiko@xxxxxxxxxxxxx> wrote:
> On Fri, May 09, 2008 at 11:43:05AM -0400, J. Bruce Fields wrote:
> > I don't think the server stopped responding to clients in the case
> > Miklos described.
>
> Okay. Well, one month later, it happened again to me.
>
> > Perhaps a sysrq-T dump of lockd would show where (and whether) it's
> > blocked? (So once lockd stops responding, log into the server, run
> > "echo t >/proc/sysrq-trigger", and collect the output from the logs,
> > especially the stacktrace for the lockd process).
>
> This time I did a ps auxww locking for the lockd process. And guess
> what?
>
> root 6323 0.0 0.0 0 0 ? D Jun01 0:50 [lockd]
>
> I wonder why it's in the D state. I also wonder if there's a way to get
> it back once it's in this state -- without reloading the kernel module
> or rebooting, I guess.
>
> I've collected a trace, at any rate, but lockd isn't even listed in it --
> I can send it in if it makes sense.
>
That's not atypical at all. syslog uses unreliable transport. When you
send it a flood of data (say, with a sysrq-t) some of it can be lost.
Usually I recommend dumping the data straight out of the ring buffer
from a sysrq-t:
# dmesg > /tmp/sysrq-t.out
...or something. You might still lose stuff that got pushed out of the
ring buffer, but the stuff that is there will at least be complete.
> What sort of debugging can I do to figure out what's wrong here?
>
You'll really need that sysrq-t info...or a core dump, or to run a
debugger on the running kernel (like Wendy recommended).
> (This is a dual-Xeon running:
>
> Linux anthem 2.6.22-14-generic #1 SMP Tue Feb 12 07:42:25 UTC 2008 i686 GNU/Linux)
There were some patches that went into 2.6.25 (I think) that fix
problems that could cause lockd to hang in some cases. This patch,
in particular, may be of interest:
Subject: [PATCH 1/4] NLM: set RPC_CLNT_CREATE_NOPING for NLM RPC clients
Cheers,
--
Jeff Layton <jlayton@xxxxxxxxxx>
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