I looked into the code of test_execute_multiple_tasks and designate/worker/processing.py from which the executor was initialized. I have converted the test case code removing the project related code as a standalone script. I hope the attached code is the minimal code required. The change from Queue to SimpleQueue was made with commit : ab74504346a6e2569b3255b7b621c589716888c4 and relevant issue is https://bugs.python.org/issue32576 .

I ran the test code by checking out each commit obtained by `git log --oneline --format="%h" Lib/concurrent/futures/thread.py` . The tests finish successfully without any hanging as below

Testing on commit :  c4b695f
Finished Tasks ['UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask']s in 0.0012586116790771484fs
Testing on commit :  ab74504
Finished Tasks ['UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask']s in 0.0013058185577392578fs
Testing on commit :  63ff413
Finished Tasks ['UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask']s in 0.0012793540954589844fs
Testing on commit :  bc61315
Finished Tasks ['UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask']s in 0.0013325214385986328fs
Testing on commit :  a3d91b4
Finished Tasks ['UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask']s in 0.0012831687927246094fs
Testing on commit :  15f44ab
Finished Tasks ['UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask']s in 0.0013515949249267578fs
Testing on commit :  50abe87
Finished Tasks ['UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask']s in 0.0020570755004882812fs
Testing on commit :  cfd4661
Finished Tasks ['UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask']s in 0.0012753009796142578fs
Testing on commit :  20efceb
Finished Tasks ['UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask']s in 0.0012905597686767578fs
Testing on commit :  6b97374
Finished Tasks ['UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask']s in 0.001275777816772461fs
Testing on commit :  04842a8
Finished Tasks ['UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask']s in 0.0014278888702392578fs
Testing on commit :  27be5da
Finished Tasks ['UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask']s in 0.0013408660888671875fs
Testing on commit :  c13d454
Finished Tasks ['UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask']s in 0.0014138221740722656fs
Testing on commit :  81c4d36
Finished Tasks ['UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask', 'UnnamedTask']s in 0.0013227462768554688fs


Can you please check if I am correct on the above approach?

Thanks