Re: Still getting NFS client locking up

On Mon, 10 Nov 2003, Matt Smith wrote:

> I can certainly spend some time trying to get some proper debug based on
> what you have said in your email. I shall look into setting up a serial
> console etc. 
> 
> In the meantime another piece of information which might be helpful is
> this. Looking at the wtmp to see when I rebuilt my world/kernel I can
> see this: 
> 
> reboot           ~                         Tue Oct 21 20:44
> reboot           ~                         Wed Oct 15 19:36
> 
> (These times are in BST which is +5 hours from east coast US). 
> 
> On the Oct 15th kernel NFS was working perfectly (and before that). From
> the Oct 21st kernel it has always locked up in this way. So something
> between those two dates was commited which broke this for us. Another
> way of me debugging this I guess is to backtrack my world to each date
> in between systematically and find the exact date it breaks and look at
> the commits. 

Hmm.  The one other thing that might be worth trying, and this is pretty
time-consuming, is attempting to narrow down the threshold kernel change
that caused the failures to start.  Typically, this is done using a binary
search (i.e., find two dates -- one that the kernel works, the other that
it doesn't -- split the difference, repeat until narrowed down to a range
of commits that can be individually inspected).  This way we could try to
identify some suspect changes that could be backed out locally
individually to narrow it down.  The likely categories of commits that
might be worth looking at probably include:

(1) Changes specifically to the network drivers that you're using.
(2) Changes to the network stack, especially relating to locking and
    timeouts.  (3) Changes to the NFS client and server code.
(4) Changes in general to VFS and buffer cache locking.

We've had a lot of commits in all of these categories, so narrowing it
down would be a useful way to help figure it out...

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert_at_fledge.watson.org      Network Associates Laboratories