On-Line Control and Deadlock-Avoidance in a Page-Parallel Multiprocessor Rasterizer

A rasterizer converts a document described in some page-description language into a sequence of full-page bitmaps (pagemaps), which can then be printed or displayed. The Page-Parallel rasterizer harnesses multiple processors to work on the same document, thereby permitting cost-effective high-speed rasterization of complex documents. Any given page is processed by a single processor, hence the name. For performance reasons, it is desirable to permit out-of-order rasterization as well as to share memory and computation results among the processors. However, this can result in deadlock. This paper presents on-line algorithms for controlling the rasterizer so as to avoid deadlock without being overly restrictive. We show that previously-proposed approaches for deadlock-avoidance cannot be applied directly due to a special form of nonexclusive allocation of shared resources. We then present a solution, thereby extending the applicability of deadlock-avoidance. We expect our approach to be useful in a variety of similar situations that may occur in other applications.