I have tested it in a step by step manner. On my machine everything works fine with point_search.
And moreover it is just a concept code. As almost everything that can be found in the open-source domain.
What is the purpose of your presence here?
That's pretty much how MT bugs present themselves: Heisenbugs that eventually manifest sooner or later. So your code is conceptually broken, even if it passes your tests. Also, are you aware that debugging a MT program is pretty much useless when running concurrent threads, especially if you have breakpoints that are reached one at a time? So of course everything works fine in that scenario, since debugging a concurrent function is basically identical as if running it single-threaded. Tests are not even needed to spot it as a bug. This is simple CS 101.
Well, my presence here is definitely not to show off broken code to n00bz that think it actually works correctly, while calling other people that know their thing as main-branch BS-ers. See it as you wish, and take from it what you want.