"Failed to read cmd on fd" errors since mod_tile update on 2nd June

I have a fairly standard Ubuntu 14.04 based map server, set up as per http://wiki.openstreetmap.org/wiki/User:SomeoneElse/Ubuntu_1404_tileserver .

I installed it on 26th April, and everything worked as expected. On 2nd June I updated mod_tile from github and started seeing "Failed to read cmd on fd" errors in syslog:

Jun 9 12:20:52 ubuntuvm38 renderd[21354]: DEBUG: Got incoming request with protocol version 2
Jun 9 12:20:52 ubuntuvm38 renderd[21354]: DEBUG: Got command RenderPrio fd(14) xml(default), z(18), x(130734), y(85209), mime(image/png), options()
Jun 9 12:20:55 ubuntuvm38 renderd[21354]: DEBUG: DONE TILE default 18 130728-130735 85208-85215 in 2.407 seconds
Jun 9 12:20:55 ubuntuvm38 renderd[21354]: DEBUG: Sending render cmd(3 default 18/130735/85209) with protocol version 2 to fd 8
Jun 9 12:20:55 ubuntuvm38 renderd[21354]: DEBUG: Failed to read cmd on fd 8
Jun 9 12:20:55 ubuntuvm38 renderd[21354]: DEBUG: Connection 0, fd 8 closed, now 5 left

This doesn't stop it working (all tiles are still being rendered as expected) but it does seem odd. Other server updates between 26th April and 2nd June include Ubuntu apt-get updates, a database reload from a new PBF file, but no changes to osm2pgsql style or (presumably) database columns etc.

http://forum.openstreetmap.org/viewtopic.php?id=25587

(from May 23rd) looks like it might be a similar issue.

Start with renderd and the reported syslog sequence, following the connection handling around the "Failed to read cmd on fd" message. Reproduce or trace the request and connection-close path, then verify that the error is resolved without interrupting tile rendering.