Read-Copy-Update

Definitions

1. A synchronization mechanism used heavily in the Linux kernel that allows readers to access shared data structures without acquiring any locks, while writers create a modified copy and atomically swap the pointer, deferring reclamation of old data until all pre-existing readers have completed (a grace period). RCU provides near-zero overhead for reads at the cost of deferred and more complex writes.

   In plain English: A technique where readers never have to wait for a lock — writers make a fresh copy of the data and only clean up the old version once everyone is done reading it.

   Example: "The routing table uses RCU so packet forwarding on every CPU core reads the table lock-free, and route updates just swap in a new copy after a grace period."

Related Terms

• MVCC
• semaphore
• Elixir
• Erlang
• Log Structured Merge Tree
• Memory Fence
• Memory Model
• Memory Order
• Transactional Memory