Lesson plan

read-modify-write

In computer science, read–modify–write is a class of atomic operations (such as test-and-set, fetch-and-add, and compare-and-swap) that both read a memory location and write a new value into it simultaneously, either with a completely new value or some function of the previous value. These operations prevent race conditions in multi-threaded applications. Typically they are used to implement mutexes or semaphores. These atomic operations are also heavily used in non-blocking synchronization. Read–modify–write instructions often produce unexpected results when used on I/O devices, as a write operation may not affect the same internal register that would be accessed in a read operation. This term is also associated with RAID levels that perform actual write operations as atomic read–modify–write sequences. Such RAID levels include RAID 4, RAID 5 and RAID 6.

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Article summary

In computer science, read–modify–write is a class of atomic operations (such as test-and-set, fetch-and-add, and compare-and-swap) that both read a memory location and write a new value into it simultaneously, either with a completely new value or some function of the previous value. These operations prevent race conditions in multi-threaded applications. Typically they are used to implement mutexes or semaphores. These atomic operations are also heavily used in non-blocking synchronization. Read–modify–write instructions often produce unexpected results when used on I/O devices, as a write operation may not affect the same internal register that would be accessed in a read operation. This term is also associated with RAID levels that perform actual write operations as atomic read–modify–write sequences. Such RAID levels include RAID 4, RAID 5 and RAID 6.

Key claims

  1. P1269: Q9135 — source: Wikidata · confidence 0.95
  2. P279: Q513932 — source: Wikidata · confidence 0.95
  3. P6366: 37918660 — source: Wikidata · confidence 0.95
  4. P646: /m/0dtz4t — source: Wikidata · confidence 0.95

Discussion questions

  1. Summarise the article in your own words. Which single claim would you verify first, and why?
  2. The record states that the P1269 is "Q9135". What evidence would count against this claim?
  3. The record states that the P279 is "Q513932". What evidence would count against this claim?
  4. The record states that the P6366 is "37918660". What evidence would count against this claim?
  5. The record states that the P646 is "/m/0dtz4t". What evidence would count against this claim?
  6. Which claim in this article is most likely to be revised as the sources update? How would you check its current status?
  7. If two sources disagreed about one of these facts, what would you need in order to trust one over the other?

Bibliography

No sources recorded.

Key claims and bibliography are generated from the same tracked claims and sources as the article page.