Start by clarifying requirements (frequency range, callback duration, cancellation semantics) and then outline a design using a priority queue of scheduled tasks with a condition variable for timing. Discuss thread-safety mechanisms (mutex, atomic flags) and safe cancellation via shared state, then analyze trade-offs and potential pitfalls like drift and callback blocking.
Pro tip: Emphasize that cancellation must be safe even if the callback is currently executing; propose using a shared atomic flag checked by the callback or a cancellation token, and mention that the scheduler should not hold locks while invoking callbacks to avoid deadlocks.
Ask about expected frequency range, callback execution time, cancellation semantics (immediate vs. after current execution), and whether multiple callbacks can run concurrently. This ensures the design meets the actual needs.
Propose a priority queue (min-heap) of tasks ordered by next execution time, protected by a mutex. Use a condition variable to sleep until the next task is due, allowing efficient waiting and wake-up on new tasks or cancellation.
Describe the worker thread loop: lock, wait until next task is due, pop due tasks, unlock, execute callbacks, then reschedule periodic tasks by computing the next time (e.g., based on start time to avoid drift).
Explain cancellation: mark the task as cancelled (e.g., via an atomic flag or shared pointer) and remove it from the queue if not yet executed. If executing, the callback should check the flag to abort early; the scheduler should not hold locks during callback execution.
Analyze trade-offs: using a single worker thread vs. thread pool, drift vs. fixed-rate scheduling, and lock contention. Mention edge cases: callback throwing exceptions, system clock changes, and high-frequency scheduling.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.