Whenever a client gracefully disconnects from smbd, a message such as the following is added to log.smbd:
[2015/11/10 12:55:11.809824, 1, pid=1721] ../source3/lib/util.c:1971(pid_to_procid)
pid_to_procid: messaging_dgm_get_unique failed: No such file or directory
To reproduce, for example, execute:
smbclient //server/share -U user%password -c 'ls'
and check the server's log.smbd.
False alarm - the log was on master branch, not on v4-3-test.