The Santa Claus Problem is perhaps the most charming of all classic concurrency problems. Introduced by John Trono in 1994, it combines barrier-style synchronization with priority scheduling in an engaging holiday theme.

Santa sleeps until awakened by either all nine reindeer returning from vacation or three elves needing help. Crucially, reindeer have priority over elves since delivering toys is more important than answering questions.

What makes this problem compelling is its multi-layered complexity. You need group formation (9 reindeer or 3 elves), mutual exclusion (only one group interacts with Santa at a time), priority (reindeer before elves), and starvation prevention (elves can't wait forever).

This combination mirrors real-world systems like priority job schedulers, group-based resource allocation, and tiered service handling.

Problem Statement