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. Online algorithms are presented for controlling the rasterizer so as to avoid deadlock without being overly restrictive. It is shown that previously proposed approaches for deadlock avoidance cannot be applied directly due to a special form of nonexclusive allocation of shared resources. A solution is given, thereby extending the applicability of deadlock avoidance. The approach should be useful in a variety of similar situations that may occur in other applications