Start by clarifying the requirements: two functions (buy and sell) that atomically update a shared stock count, preventing overselling. Then design a solution using a mutex to protect the critical sections, ensuring that the sell operation checks the available quantity before decrementing. Finally, discuss potential optimizations and trade-offs, such as using read-write locks or lock-free approaches.
Pro tip: Mention that you would use a mutex (or read-write lock) to protect the shared state, but also discuss the trade-off between lock granularity and performance, and consider using condition variables to handle waiting when stock is insufficient.
Ask whether the stock count is an integer, whether buy and sell are the only operations, and whether blocking or non-blocking behavior is desired when stock is insufficient.
Propose a shared integer for stock count and a mutex (or read-write lock) to protect it. Explain that all accesses to the stock count must be within a critical section.
Write pseudocode for buy (increment stock under lock) and sell (check stock > 0, then decrement under lock). Ensure atomicity by holding the lock for the entire operation.
Address scenarios like selling when stock is zero, multiple threads contending, and potential deadlocks. Mention using condition variables to wait for stock availability if needed.
Compare mutex vs. read-write lock vs. atomic operations. Discuss performance implications and suggest alternatives like lock-free approaches using compare-and-swap if appropriate.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.