read-write semaphore

OPPO Kernel Craftsman

Aug 12, 2022 · Fundamentals

Understanding Linux rwsem: Mechanisms, Data Structures, and Optimistic Spinning

Linux rwsem is a read‑write semaphore that lets multiple readers or a single writer hold the lock, using a count field, owner pointer, optimistic‑spin queue (osq), and protected wait list; it provides fast, medium, and slow acquisition paths with handoff and optimistic spinning to reduce sleep latency compared to mutexes and spinlocks.