How to debug rc hangs?

[Brooks Davis]

On Wed, Oct 24, 2007 at 12:06:08AM +1000, John Marshall wrote:
>  Mike Telahun Makonnen wrote:
> > On 10/23/07, John Marshall <John.Marshall at riverwillow.com.au> wrote:
> >> I have tried setting rc_debug="YES" in rc.conf but that doesn't show me
> >> any more than I already know (e.g. last line before mountd hang is:
> >> "/etc/rc: DEBUG: run_rc_command: doit: /usr/sbin/mountd -l"
> > It seems to me that if it's getting this far, that the problem probably is
> > not in rc.d. The next thing it does after that debug message is eval the 
> > $doit
> > line you saw, so either the eval command is missbehaving or the problem
> > is with the daemon and not rc.d. What does CTR-t say when it hangs? Also,
> > I noticed all three programs you listed are network daemons. My guess is
> > they are not actually hung, they only *appear* to hang because they're 
> > wating
> > on some sort of network resource (DNS maybe?).
> 
>  Thanks Mike,
> 
>  The ctrl-T tip is the kind of information I'm looking for. My primary reason 
>  for posting is to find out what tools/switches/hooks are available to help 
>  troubleshoot this kind of problem, rather than asking somebody else to solve 
>  it.
> 
>  Having said that, ctrl-T shows:
>   load: 0.74 cmd: mountd 576 [nanslp] 0.00u 0.00s 0% 1428k
>   load: 0.25 cmd: mountd 576 [nanslp] 0.00u 0.00s 0% 1432k
>   load: 0.12 cmd: mountd 576 [nanslp] 0.00u 0.00s 0% 1432k
> 
>  ...which lends weight to my suspicion that a pre-requisite resource is not 
>  yet available - and, perhaps, hasn't yet started due to a circular 
>  dependency? As I hinted, my plan is to drill down into the PROVIDE/REQUIRE 
>  labyrinth and work by trial and error (with a reboot in between each error). 
>  I'm happy to do that but I'm hoping that I might be able to use this 
>  situation to learn of more elegant ways to diagnose the problem.
> 
>  ...and to reiterate, this is on 7.0-BETA1 (built Saturday morning) and all 
>  this was working without any intervention on 6.2-RELEASE.

When I see processes stalled on nanslp at boot it's usually when my network is
messed up in some way.  I think it's stuck in the resolver trying to look things
up.

-- Brooks
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