Read/Write Lock

A read/write lock distinguishes between shared read access, allowing multiple threads simultaneously, and exclusive write access, allowing only one thread. Multiple threads can hold a read lock simultaneously because no thread is modifying the data, making concurrent reads safe. When a write lock is acquired, all existing readers are evicted and new read requests are blocked until the write completes. Threads that were blocked during a write lock must not assume the data is unchanged when they regain access and may need to restart or re-read from the updated state. The read/write lock pattern optimizes for read-heavy workloads while still protecting correctness during writes.