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The code using a java.util.concurrent.ReentrantReadWriteLock is similar to that for native synchronization. However, for safety, the locks should be used in a try/finally block so that early exit such as java.lang.Exception throwing or break/continue will be sure to pass through the
The location (in memory) of the code for handling an exception need not be located within (or even near) the region of memory where the rest of the function's code is stored. So if an exception is thrown then a performance hit – roughly comparable to a function call [24] – may occur if the necessary exception handling code needs to be ...
As the queue is a concurrent object shared between threads, accesses to it must be made atomic, because the queue can be put into an inconsistent state during the course of the queue access that should never be exposed between threads. Thus, any code that accesses the queue constitutes a critical section that must be synchronized by mutual ...
Since JDK 1.2, Java has included a standard set of collection classes, the Java collections framework. Doug Lea, who also participated in the Java collections framework implementation, developed a concurrency package, comprising several concurrency primitives and a large battery of collection-related classes. [19]
Thread safety guarantees usually also include design steps to prevent or limit the risk of different forms of deadlocks, as well as optimizations to maximize concurrent performance. However, deadlock-free guarantees cannot always be given, since deadlocks can be caused by callbacks and violation of architectural layering independent of the ...
Reentrant code may not modify itself without synchronization. The operating system might allow a process to modify its code. There are various reasons for this (e.g., blitting graphics quickly) but this generally requires synchronization to avoid problems with reentrancy. It may, however, modify itself if it resides in its own unique memory.
Some concurrency control strategies avoid some or all of these problems. For example, a funnel or serializing tokens can avoid the biggest problem: deadlocks. Alternatives to locking include non-blocking synchronization methods, like lock-free programming techniques and transactional memory. However, such alternative methods often require that ...
In concurrent programming, concurrent accesses to shared resources can lead to unexpected or erroneous behavior. Thus, the parts of the program where the shared resource is accessed need to be protected in ways that avoid the concurrent access. One way to do so is known as a critical section or critical region. This protected section cannot be ...