Read-copy-update

In <a href="/facts/Computer_science/lN3pEyPz">computer science</a>, read-copy-update (RCU) is a <a href="/facts/Synchronization_(computer_science)/n7ID76uM">synchronization</a> mechanism that avoids the use of <a href="/facts/Lock_(computer_science)/e3a9gnJT">lock</a> primitives while multiple <a href="/facts/Thread_(computing)/hh8WHyPd">threads</a> concurrently read and update elements that are linked through <a href="/facts/Pointer_(computer_programming)/fPoNzy9b">pointers</a> and that belong to shared <a href="/facts/Data_structure/yNsNvL1I">data structures</a> (e.g., <a href="/facts/Linked_lists/Ik4JTgJW">linked lists</a>, <a href="/facts/Tree_(data_structure)/RcXz9noF">trees</a>, <a href="/facts/Hash_table/Ht4ptDPF">hash tables</a>).
Whenever a thread is inserting or deleting elements of data structures in <a href="/facts/Shared_memory/zmpH7WuV">shared memory</a>, all readers are guaranteed to see and traverse either the older or the new structure, therefore avoiding inconsistencies (e.g., dereferencing <a href="/facts/Null_pointer/66zwVEfL">null pointers</a>).
It is used when performance of reads is crucial and is an example of <a href="/facts/Space%E2%80%93time_tradeoff/zMRR67q9">space–time tradeoff</a>, enabling fast operations at the cost of more space. This makes all readers proceed as if there were no <a href="/facts/Synchronization_(computer_science)/n7ID76uM">synchronization</a> involved, hence they will be fast, but also making updates more difficult.

Read-copy-update open-in-new

Read-copy-update