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In software engineering, double-checked locking (also known as "double-checked locking optimization" [1]) is a software design pattern used to reduce the overhead of acquiring a lock by testing the locking criterion (the "lock hint") before acquiring the lock. Locking occurs only if the locking criterion check indicates that locking is required.
First, the async keyword indicates to C# that the method is asynchronous, meaning that it may use an arbitrary number of await expressions and will bind the result to a promise. [1]: 165–168 The return type, Task<T>, is C#'s analogue to the concept of a promise, and here is indicated to have a result value of type int.
The goal is to introduce concurrency, by using asynchronous method invocation and a scheduler for handling requests. [2] The pattern consists of six elements: [3] A proxy, which provides an interface towards clients with publicly accessible methods. An interface which defines the method request on an active object. A list of pending requests ...
In computer science, a semaphore is a variable or abstract data type used to control access to a common resource by multiple threads and avoid critical section problems in a concurrent system such as a multitasking operating system.
Reduce the overhead of acquiring a lock by first testing the locking criterion (the 'lock hint') in an unsafe manner; only if that succeeds does the actual locking logic proceed. Can be unsafe when implemented in some language/hardware combinations. It can therefore sometimes be considered an anti-pattern. Yes — Event-based asynchronous
lock contention: this occurs whenever one process or thread attempts to acquire a lock held by another process or thread. The more fine-grained the available locks, the less likely one process/thread will request a lock held by the other. (For example, locking a row rather than the entire table, or locking a cell rather than the entire row);
In computer science, futures, promises, delays, and deferreds are constructs used for synchronizing program execution in some concurrent programming languages.Each is an object that acts as a proxy for a result that is initially unknown, usually because the computation of its value is not yet complete.
In this particular case, the processor can choose to not lock until two threads actually conflict with each other. [ 3 ] A simpler version of the test can use the cmpxchg instruction on x86, or the __sync_bool_compare_and_swap built into many Unix compilers.