Editing Mutual exclusion (section)

===Software solutions===
In addition to hardware-supported solutions, some software solutions exist that use [[busy waiting]] to achieve mutual exclusion. Examples include:
* [[Dekker's algorithm]]
* [[Peterson's algorithm]]
* [[Lamport's bakery algorithm]]<ref>{{cite journal|last=Lamport|first=Leslie|title=A new solution of Dijkstra's concurrent programming problem|journal=Communications of the ACM|date=August 1974|volume=17|issue=8|pages=453–455|doi=10.1145/361082.361093|s2cid=8736023|doi-access=free}}</ref>
* [[Szymański's algorithm]]
* Taubenfeld's black-white bakery algorithm<ref name="Taubenfeld:2004" />
* [[Maekawa's algorithm]]

These algorithms do not work if [[out-of-order execution]] is used on the platform that executes them. Programmers have to specify strict ordering on the memory operations within a thread.<ref>{{cite journal|last=Holzmann|first=Gerard J.|author2=Bosnacki, Dragan|title=The Design of a Multicore Extension of the SPIN Model Checker|journal=IEEE Transactions on Software Engineering|date=1 October 2007|volume=33|issue=10|pages=659–674|doi=10.1109/TSE.2007.70724|s2cid=9080331|url=https://pure.tue.nl/ws/files/2357048/Metis212904.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://pure.tue.nl/ws/files/2357048/Metis212904.pdf |archive-date=2022-10-09 |url-status=live}}</ref>

It is often preferable to use synchronization facilities provided by an [[operating system]]'s multithreading library, which will take advantage of hardware solutions if possible but will use software solutions if no hardware solutions exist. For example, when the operating system's [[lock (computer science)|lock]] library is used and a thread tries to acquire an already acquired lock, the operating system could suspend the thread using a [[context switch]] and swap it out with another thread that is ready to be run, or could put that processor into a low power state if there is no other thread that can be run. Therefore, most modern mutual exclusion methods attempt to reduce [[Latency (engineering)|latency]] and busy-waits by using queuing and context switches. However, if the time that is spent suspending a thread and then restoring it can be proven to be always more than the time that must be waited for a thread to become ready to run after being blocked in a particular situation, then [[spinlock]]s are an acceptable solution (for that situation only).{{citation needed|date=August 2015}}