As a note to myself: adding a simple print to the multiprocessing.Queue 
put method, I can see the calls occurring from the children in order, 
for example:

obj:  0.025193 [proc1] Got lock
obj:  0.227725 [proc1] Released lock
obj:  0.228401 [proc2] Got lock
obj:  0.430501 [proc2] Released lock
obj:  0.431082 [proc0] Got lock
obj:  0.633048 [proc0] Released lock
obj:  0.633723 [proc4] Got lock
obj:  0.835692 [proc4] Released lock
obj:  0.836262 [proc3] Got lock
obj:  1.038197 [proc3] Released lock
obj:  1.038753 [proc1] Got lock
obj:  1.239288 [proc1] Released lock
obj:  1.240079 [proc2] Got lock
obj:  1.440773 [proc2] Released lock
obj:  1.441577 [proc0] Got lock
obj:  1.642142 [proc0] Released lock
obj:  1.642959 [proc4] Got lock
obj:  1.843331 [proc4] Released lock
obj:  1.844178 [proc3] Got lock
obj:  2.044549 [proc3] Released lock

Also attaching the process-based script