Michael Nonemacher

Most non-trivial applications involve high degrees of concurrency and many layers of abstraction. Concurrency is associated with resource contention and an increase in deadlock conditions. The multiple layers of abstraction make it more difficult to isolate and fix the deadlock conditions. Generally, a deadlock happens when two or more concurrent threads of execution each hold a resource and request another resource. Since neither one continues until it acquires the resource, we say each specific thread is blocked; if each thread is blocked on a resource that is held by another thread in the same group, we say the group of threads is deadlocked. In this article, we'll discuss two broad categories of deadlocks that occur in typical non-trivial J2EE applications: "simple" database deadlocks and cross-resource deadlocks. Although the discussion is based on J2EE, it also ... (more)