Editing Read-copy-update (section)

==Name and overview==
The name comes from the way that RCU is used to update a linked structure in place. A thread wishing to do this uses the following steps:
* create a new structure,
* copy the data from the old structure into the new one, and save a [[pointer (computer programming)|pointer]] to the old structure,
* modify the new, copied, structure,
* update the global pointer to refer to the new structure,
* sleep until the operating system kernel determines that there are no readers left using the old structure, for example, in the Linux kernel, by using {{mono|synchronize_rcu()}},
* once awakened by the kernel, deallocate the old structure.

So the structure is ''read'' concurrently with a thread ''copying'' in order to do an ''update'', hence the name "read-copy update". The abbreviation "RCU" was one of many contributions by the Linux community. Other names for similar techniques include ''passive serialization'' and ''MP defer'' by [[VM (Operating system)|VM/XA]] programmers and ''generations'' by [[K42]] and [https://web.archive.org/web/20140102191807/http://www.eecg.toronto.edu/~tornado/ Tornado] programmers.