BUG #6183: FATAL: canceling authentication due to timeout

The following bug has been logged online:

Bug reference:      6183
Logged by:          Thorvald Natvig
Email address:      thorvald@medallia.com
PostgreSQL version: 9.1rc1
Operating system:   RHEL6
Description:        FATAL:  canceling authentication due to timeout
Details:

We get a lot of "FATAL:  canceling authentication due to timeout" in the
log, with accompanying closed connections to clients.

We first saw this on 9.0.4. Googling around, I saw a reference on
postgresql-hackers to
http://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=592b615d71
caac8a3504276a805a6fd024c40041

There does indeed seem to be a correlation between doing vacuum and seeing
this error.

Seeing as that commit was included in 9.1rc1, we tried upgrading to 9.1rc1
doing a full dump/restore. However, the exact same problem still remains.