Marco Bernardo and Edoardo Bontà Università di Urbino Carlo Bo - Italy Istituto di Scienze e Tecnologie dell Informazione

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1 Generating Well-Synchronized Multithreaded Programs from Software Architecture Descriptions Marco Bernardo and Edoardo Bontà Università di Urbino Carlo Bo - Italy Istituto di Scienze e Tecnologie dell Informazione

2 Overview Multithreading provides an adequate support for concurrent programming, but requires the software developer to take care of the correct synchronization and exchange of data among threads. The software developer should be provided with a suitable support for being confident in the correctness of the way in which the thread synchronization is dealt with. A complicated combination of several different synchronization techniques sleep and wakeup primitives, semaphores, monitors, etc. may be necessary. WICSA 2004 Marco Bernardo & Edoardo Bontà 2

3 An Architecture-driven Approach Developed a [Java] package of software components related to the main architectural concepts, which take care of the details of the thread synchronization in a way that is transparent to the software developer. 1. Provide an architectural description [PADL] of the multithreaded program, which specifies at a high level of abstraction the program topology in terms of thread instances and their interactions. 2. Use a translator [PADL2Java] that, from the PADL specification of the multithreaded Java program, automatically generates (a skeleton of) the program based on the Java package, in a way that guarantees the correct thread synchronization. No global variables. No passing object references while keeping a copy of them. WICSA 2004 Marco Bernardo & Edoardo Bontà 3

4 Example: Real-Time Audio Processing System start effect stop Console start stop dry_segment effect processed_segment Input Audio Sound Processor Output Audio end_of_stream end_of_stream dry_samples processed_samples WICSA 2004 Marco Bernardo & Edoardo Bontà 4

5 Example: Real-Time Audio Processing System Screenshot of a real application WICSA 2004 Marco Bernardo & Edoardo Bontà 5

6 Java packagesync: LayerArchitecture Architecture ThreadElem Port Connector public abstract class Architecture extends ThreadElem { } Advantages deriving from inheritance: Hierarchy Composition Concurrency WICSA 2004 Marco Bernardo & Edoardo Bontà 6

7 Java packagesync: LayerThreadElem Architecture ThreadElem Port Connector public abstract class ThreadElem extends Thread { } Constructors of the Thread class redefined in the ThreadElem class with the same parameters. Additional methods for easily generating Java code for the thread. WICSA 2004 Marco Bernardo & Edoardo Bontà 7

8 Java packagesync: LayerPort Architecture ThreadElem Synchronous / Asynchronous Ports: Port Connector uni - sender and - sender or - sender uni - receiver and - receiver or - receiver WICSA 2004 Marco Bernardo & Edoardo Bontà 8

9 Java packagesync: LayerConnector Architecture ThreadElem Port Connector Connector types: asynchronous-to-asynchronous asynchronous-to-synchronous synchronous-to-asynchronous synchronous-to-synchronous WICSA 2004 Marco Bernardo & Edoardo Bontà 9

10 Structure of a PADL Textual Description ARCHI_TYPE ARCHI_ELEM_TYPES ARCHI_TOPOLOGY ARCHI_ELEM_INSTANCES ARCHI_INTERACTIONS ARCHI_ATTACHMENTS Name Architectural element types: behaviors and interactions Architectural element instances Architectural interactions Architectural attachments END WICSA 2004 Marco Bernardo & Edoardo Bontà 10

11 Generating Code PADL2Java [-p/-c/-a] file1.padl file2.java import Sync; class <Element Type Name> extends ThreadElem { Sections: DEFINING CONSTRUCTOR DEFINING BEHAVIOR (skeleton) INSTANTIATING INPUT INTERACTIONS INSTANTIATING OUTPUT INTERACTIONS } class <Architecture Type Name> extends Architecture { Sections: DECLARING THREADS (element types) DECLARING ARCHITECTURAL INTERACTIONS DEFINING CONSTRUCTOR BUILDING ARCHITECTURE RUNNING ARCHITECTURE } WICSA 2004 Marco Bernardo & Edoardo Bontà 11

12 Building Architecture: Architectural Element Instances Console Input Audio Sound Processor Output Audio WICSA 2004 Marco Bernardo & Edoardo Bontà 12

13 Building Architecture: Architectural Interactions Console Input Audio Sound Processor Output Audio WICSA 2004 Marco Bernardo & Edoardo Bontà 13

14 Building Architecture: Architectural Attachments Console Input Audio Sound Processor Output Audio WICSA 2004 Marco Bernardo & Edoardo Bontà 14

15 Future Work Automatic generation of the thread behavior. Preserving the properties proved at the architectural level by means of the analysis techniques for PADL. Integrating the translator in the software tool TwoTowers. WICSA 2004 Marco Bernardo & Edoardo Bontà 15