RCU

Linux RCU Grace Periods Separate Removal from Reclamation

Read-Copy Update, commonly called RCU, is a synchronization family used throughout the Linux kernel for data that is read frequently and changed less often. Its central move is to separate two events that ordinary locking often treats as one: removing an object from a shared structure and reclaiming the memory that stored it. A writer can publish a new state or unlink an old object while readers continue through read-side critical sections. The old storage remains valid until the kernel has established that every reader that could have observed the old reference has passed through a quiescent state. That interval is an RCU grace period.