Hangs when fed a list of directories

[ariel-co]

I tried to delete a directory in parallel. It hangs like this:

ariel@section9:~/Stuff/src/libreoffice $ ls -d .ccache/*/*/ | ppss -f - -c 'rm -R $ITEM'
Apr 02 21:36:32:  
Apr 02 21:36:32:  =========================================================
Apr 02 21:36:32:                         |P|P|S|S|                         
Apr 02 21:36:32:  Distributed Parallel Processing Shell Script vers. 2.98
Apr 02 21:36:32:  =========================================================
Apr 02 21:36:32:  Hostname:     section9
Apr 02 21:36:32:  ---------------------------------------------------------
Apr 02 21:36:32:  CPU: Intel(R) Core(TM) i7-2700K CPU @ 3.50GHz
Apr 02 21:36:32:  Found 4 logic processors.
Apr 02 21:36:32:  Starting 4 parallel workers.
Apr 02 21:36:32:  ---------------------------------------------------------
Apr 02 21:36:32:  8% complete. Processed 4 of 48. Failed 0/48.

These are the remaining processes when hung:

UID        PID  PPID  C STIME TTY      STAT   TIME CMD
ariel    13314  2944  0 21:36 pts/5    S+     0:00 bash /home/ariel/bin/ppss -f - -c rm -R $ITEM
ariel    13377 13314  0 21:36 pts/5    S+     0:00 bash /home/ariel/bin/ppss -f - -c rm -R $ITEM

$PPSS_DIR/job_log is empty (see attached tarball with fake extension).

Now, PPSS works if it's prevented from detecting the directories:

ariel@section9:/tmp $ ( cd ~/Stuff/src/libreoffice; ls -d .ccache/*/*/ ) | ppss -f - -c 'rm -R ~/Stuff/src/libreoffice/$ITEM'
Apr 02 21:45:10:
Apr 02 21:45:10:  =========================================================
Apr 02 21:45:10:                         |P|P|S|S|                      
Apr 02 21:45:10:  Distributed Parallel Processing Shell Script vers. 2.98
Apr 02 21:45:10:  =========================================================
Apr 02 21:45:10:  Hostname:     section9
Apr 02 21:45:10:  ---------------------------------------------------------
Apr 02 21:45:10:  CPU: Intel(R) Core(TM) i7-2700K CPU @ 3.50GHz
Apr 02 21:45:10:  Found 4 logic processors.
Apr 02 21:45:10:  Starting 4 parallel workers.
Apr 02 21:45:10:  ---------------------------------------------------------
Apr 02 21:45:12:  100% complete. Processed 48 of 48. Failed 0/48.         
Apr 02 21:45:12:  Total processing time (hh:mm:ss): 00:00:02
Apr 02 21:45:12:  Finished. Consult /tmp/ppss/job_log for job output.

Maybe it's some sort of automagic behavior aimed at processing files, but I can't imagine what I could do with it.