![]() ![]() Frequent speaker and blogger at and semaphore differ mainly in four things:Ī spinlock is one possible implementation of a lock, namely one that is implemented by busy waiting ("spinning"). He works as a software engineer for Microsoft. For almost two decades he contributes to open-source, i.e. He focuses on data and business layers, language constructs, parallelism, databases and performance. What about the performance? Next section dives into performance. But I wouldn’t use the interning, because it’s a hack and I don’t want that in my code, especially in multithreaded code. Summaryįor me both options look the same in terms of effort. You can even add a method to remove the object from the collection (although special care has to be taken because the object might be in use). int), plus different pieces of code can use different instances. ![]() On the other hand, this gives you the option to use different keys (i.e. Additionally, you have to keep the instance around and accessible. Where the locker is instance of NamedMonitor and name is your string you want the lock to be bound to.ĭoes this have some drawbacks? Obviously, it’s something you have to write, test and “maintain” it. Public object this => _dictionary.GetOrAdd(name, _ => new object()) Īnd then you can use it. Readonly ConcurrentDictionary _dictionary = new ConcurrentDictionary() ![]() It’s easier to wrap this into tiny class to have it nicely self-contained. Using ConcurrentDictionary you can get always the same object (in this case really an object, because what smaller object to create…). The ConcurrentDictionary was introduced in. So, although it’s very straightforward, it’s also pretty dangerous. In case some other piece of code in your application uses the same technique over the same string content, deadlocks or contentions can occur. Among these philosophical concerns, there’s one (at least) from real world. ![]() Also, although improbable, the implementation can change and then you’re in trouble. Where the name is your string you want the lock to be bound to.ĭoes it have some drawbacks? Well, first, the interning was not designed for locking. How it would look like? lock (string.Intern(name)) That allows you to have an object ( string is an object) that you can always get and always get the same one, if you have an appropriate string content. NET that allows you to place a string into a table and whenever you intern the same string (same content) the reference to the string in that table is returned. And although you can come up with countless solutions, two most straightforward are the following: using interned string as an object to lock on and storing the objects in a hashtable (Dictionary in. As a result, you’re left to your own creativity to solve it. So you decide to create lock per counter, for example. Of course, you can create a global lock that will guard all the counters, but as the number of devices and counters grows, the single lock will become a bottleneck. And these counters are modified from various devices. Let’s imagine you have a bunch of counters. Spinning means, because Monitor can be put in hybrid locks category, that for a short amount of time the Monitor will try to acquire the lock by trying in a loop, hence spinning, before giving up and blocking regularly, giving up the CPU. Thread ownership supports the previous behavior and also enforces that the thread “entering” the Monitor is the thread “exiting” it (otherwise an exception is thrown). Recursion means that from the same thread you can “enter” the Monitor multiple times (and you have to also “exit” it the same amount of times). Mutual exclusivity guarantees that code “locked” using Monitor is executed always in single thread at any given time. Monitor has these four fundamental features: mutual exclusivity, recursion, thread ownership and spinning. This is often called named locks or named Monitors, because the lock is bound to some name (or similar value). One thing you might face is unknown number of locks you’re going to need and how to solve this. NET might be the most often used “locking” mechanism in C#, mostly because the lock keyword is making it so easy. NET, Multithreading/Parallelism/Asynchronous/Concurrency Tabs ↹ over ␣ ␣ ␣ spaces by Jiří Činčura Named locks (using Monitor) in. ![]()
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