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To synchronize threads, Java uses monitors, which are a high-level mechanism for allowing only one thread at a time to execute a region of code protected by the monitor. The behavior of monitors is explained in terms of locks ; there is a lock associated with each object.
For example, suppose that there are three processes, namely 1, 2, and 3. All three of them are concurrently executing, and they need to share a common resource (critical section) as shown in Figure 1. Synchronization should be used here to avoid any conflicts for accessing this shared resource.
A Java style monitor. In the Java language, each object may be used as a monitor. Methods requiring mutual exclusion must be explicitly marked with the synchronized keyword. Blocks of code may also be marked by synchronized. [6]
This approach is characteristic of functional programming and is also used by the string implementations in Java, C#, and Python. (See Immutable object.) The second class of approaches are synchronization-related, and are used in situations where shared state cannot be avoided: Mutual exclusion
In computer science, read-copy-update (RCU) is a synchronization mechanism that avoids the use of lock primitives while multiple threads concurrently read and update elements that are linked through pointers and that belong to shared data structures (e.g., linked lists, trees, hash tables).
As an example use case of compare-and-swap, here is an algorithm for atomically incrementing or decrementing an integer. This is useful in a variety of applications that use counters. The function add performs the action *p ← *p + a, atomically (again denoting pointer indirection by *, as in C) and returns the final value stored in the counter.
In computer science, message passing is a technique for invoking behavior (i.e., running a program) on a computer.The invoking program sends a message to a process (which may be an actor or object) and relies on that process and its supporting infrastructure to then select and run some appropriate code.
For example, Lee and Sangiovanni-Vincentelli have demonstrated that a so-called "tagged-signal" model can be used to provide a common framework for defining the denotational semantics of a variety of different models of concurrency, [11] while Nielsen, Sassone, and Winskel have demonstrated that category theory can be used to provide a similar ...