The previous revision used multiprocessing but still relied on timing
("second process waited at least N seconds") which flakes on CI where
spawn overhead eats into the hold window. Linux CI observed the second
process report a 0.088s wait — below the 0.1s threshold — even though
the lock behavior was correct; spawn was just slow enough that the
first process had nearly finished holding when the second got past
its own spawn.
Switch to effect-based verification: each worker logs its
[enter_time, exit_time] inside the critical section, and the test
asserts the two intervals are disjoint after sorting. A broken lock
would produce overlapping intervals regardless of spawn latency; a
working lock cannot.
Also removed the mp.Queue since we no longer pass timing data back.
Igor Lins e Silva
1dc20e307b