DragonFlyBSD

I have recently found a few blocked dovecot processes on a DragonFly 3.3 imap server.

Software: Dovecot-2.1.15, DragonFly-3.3 from March 11, 2013

ps auxw output:

user1 3361 0.0 0.0 31416 2804 ?? D1LM Fri03PM 0:01.42 imap: [user1 2001:7a8:1170:201:225:90ff:f
user1 3499 0.0 0.0 31484 2800 ?? D3LM Fri03PM 0:00.51 imap: [user1 2001:7a8:1170:201:225:90ff:f

top output:

PID USERNAME      NICE  SIZE    RES    STATE CPU  TIME   CTIME    CPU COMMAND
 3361 user1           0    31M  2804K    clock  1   0:01    0:01  0.00% imap
 3499 user1           0    31M  2800K    clock  3   0:00    0:00  0.00% imap

The 'clock' state may be set from vfs_cache.c:356:

error = tsleep(&ncp->nc_locktd, PINTERLOCKED,
                   "clock", nclockwarn);

I have not found any other obvious place in sys/ using it.

The dovecot user stores emails on a Maildir directory on a HAMMER filesystem.
All files in the Maildir/ directory seem to be normally accessible; I could read it completely and store its
content into a tar archive without any issue.