On my system, issuing for file in *.JPG; do nice -19 display -resize 25% $file &; done in a directory on an SMBFS-mount with some 80 files produces a number of processes which only run for a fraction of a second and then all get stuck: % ps PID TT STAT TIME COMMAND 2069 1 DNL 0:00,27 display -resize 25% 1.JPG 2070 1 DNL 0:00,26 display -resize 25% 2.JPG 2071 1 DNL 0:00,27 display -resize 25% 3.JPG […] The processes cannot be killed, and all further file operations on the same mount, even umount -f, will get stuck, too. Even worse, this problem even manages to make clean rebooting impossible, and I have to use reboot -q instead. It might date back as far as 2005, see: https://lists.freebsd.org/pipermail/freebsd-questions/2005-October/101035.html
^Triage: I'm sorry that this PR did not get addressed in a timely fashion. By now, the version that it was created against is long out of support. Please re-open if it is still a problem on a supported version.