I don't think this an unreasonable puzzle for a role that involves problem-solving or security.

You can read the code, figure out what primitives you have, translate the problem into something simple (I like card and board games), then map it back.

Problem: two processes each do this ten times: - read the counter - do any number of other things in other processes - write back what you read, plus one.

Game: You have two piles of cards. Each card costs 1 move to play, but lets you discard any number of cards from other piles at the same time.

Solution: play one red card, discarding everything but one blue card. Play the single remaining blue card, discarding the leftover red cards.

Back: process 1 reads, process 2 runs 9 steps, process 1 writes, process 2 reads, process 1 finishes, process 2 writes.