So here's what we know now:
 - the reason I've not been able to reproduce this problem is because my mounts 
are listed by name, and are *not* resolvable before the network is up; so the 
mount helper fails immediately with an unresolvable name (since mount correctly 
detects the network is down, and propagates this failure up the stack).  In the 
submitter's case, the name *is* resolvable (via /etc/hosts) before the network 
is up, which means that the mount helper gets an IP to pass down to the kernel, 
which it does... and the kernel's behavior in response to a mount request for 
an unreachable IP is less than stellar (to wit: it does *not* immediately 
return an error).
 - even after sorting out this problem, the latest boot logs still show a 
problem getting all the way through the mounts.  The mounts all succeed and are 
reported back, but the 'mounted' events don't finish for all of these, either 
because something in upstart is blocking them or because they get lost along 
the way in mountall.

My current theory as to why the mounted events are being lost is because
of a known issue with SIGUSR1 triggering duplicate 'mounting' events
(bug #1048017)... perhaps if one of these 'mounting' events is being
triggered late for the mount (which appears to be the case, from the
logs), it is blocking the 'mounted' event from happening correctly.
This is supported by the fact that the logs show an extra 'mounting'
event for the mounts that aren't correctly recorded, vs. the ones that
are correctly recorded.

Of further note, in the latest log we're getting 3/8 remote mounts
recorded.  But two of these are actually events for the *same*
mountpoint.  I've seen this issue previously but don't have a bug report
open for it; it's certainly not the cause of boot hangs, but it could
cause mountall to emit the 'filesystem' event too early.

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https://bugs.launchpad.net/bugs/1233610

Title:
  boot process hangs very often when NFS shares are used

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