← Cloudkitchens Interview Insights
Start by clarifying requirements: reentrancy, fairness, condition variables, and performance. Then design a lock using a mutex and condition variable, tracking owner thread and hold count. Finally, discuss trade-offs and test with complex scenarios like recursive locking and multiple condition variables.
Pro tip: Mention that reentrancy is about the same thread acquiring the lock multiple times, and that you need to track the owning thread and a hold count. Also, highlight that condition variables must be tied to the lock and that spurious wakeups require while loops.
Ask about reentrancy, fairness, condition variables, and performance expectations. Confirm the programming language and environment.
Use a mutex and condition variable to protect shared state. Track the owner thread ID and a hold count to support reentrancy.
In lock(), if current thread is owner, increment hold count; else wait until lock is free, then set owner and hold count to 1. In unlock(), decrement hold count; if zero, clear owner and signal condition variable.
Provide wait(), signal(), and broadcast() methods that operate on the lock. Ensure wait() releases the lock fully and reacquires it upon wakeup, preserving reentrancy.
Talk about fairness vs. performance, potential deadlocks, and test with recursive locking, multiple threads, and condition variable usage.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.