[Dovecot] recursive locks

[Mike Abbott]

How can a dovecot-2 plugin safely use file-locks or file-dotlocks when the processes into which it plugs handle multiple connections?  (Via, e.g.,
service imap {
  client_limit = N
  service_count = 0
})
Dovecot's file-locks and file-dotlocks do not appear to support nesting/recursion.

For instance, squat_trie_lock().  Imagine one user is connected to a single imap process twice.