“Alfonse, wait here for my signal!”

Abstract

At first glance, Java monitors appear easy to use. However, a deeper analysis reveals that they are surprisingly tricky, suffer from subtle race conditions, and are actually a low-level synchronization tool in stark contrast to the reputation Java has as a modern well-engineered language. The programmer is responsible for building safe and robust synchronization structures from Java monitors.

“Alfonse, give me a call!”

“…Although called a monitor [10], Java's synchronization primitive is low level and error prone, lacking multiple condition variables and suffering from subtle race conditions between signals (notifications) and program-initiated thread interrupts [7].…”

“Alfonse, you have a message!”

“…Although Java's monitors appear easy to use, they are surprisingly tricky and suffer from subtle race conditions [9]. For example, suppose several threads are blocked Permission to make digital or hard copies of all or part,of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advant -age and that copies bear this notice and the full citation on the first page.…”

Distributed BACI: a toolkit for distributed applications

“…exclusion toolkit, similar in spirit to the BACI work described in this paper. The author notes, however, that the Java monitor suffers from subtle race conditions [33], which may be confusing to the users of the toolkit. BACI does not, on the other hand, suffer from any subtle race conditions.…”