Realtime Java Intro

Intro

• US NIST coordinated guiding principles and set of requirements for the RealtimeJava.
• Guiding principles was to support current real time practices and and facilitate advances in state of the art real time implementation.

Current Practice

• Fixed priority and round robin scheduling
• Mutual exclusion locking (avoiding priority inversion)
• Inter-thread communication (e.g. semaphores)
• User-defined interrupt handlers and device drivers — including the ability to manage interrupts (e.g., enabling and disabling)
• Timeouts and aborts on running threads

Implementation Requirements

• A framework for finding available profiles (e.g. safety critical, no dynamic loading and distributed real time profiles).
• Bounded preemption latency on GC.
• A well defined model for real time Java threads.
• Communication and synchronization between real time and non real time java threads.
• Mechanisms for handling internal and external asynchronous events.
• Asynchronous thread termination.
• Mutex without blocking.
• Ability to determine if thread is real time or non real time.
• A well defined relationship between real time and non real time threads.

Guiding Principles

• Write once run anywhere.
• Be backward compatible with non real time Java programs - the RTJVM should be able to run standard java apps.
• Address current real time practice.
• Give priority to predictable execution in all design tradeoffs.
• Require no syntactic extensions to the Java language.
• Give platform implementers flexibility.