PDP 4PS : Periodic Delayed Protocol for Partitioned Systems

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1 PDP 4PS : Periodic Delayed Protocol for Partitioned Systems Authors: Antoine Jaouën Etienne Borde Laurent Pautet Thomas Robert firstname.lastname@telecom-paristech.fr

2 Introduction & Issues ontext Safety ritical systems Under standard specification (ARIN, ENELE-EN 08) Partitioned systems (space & time segregation of applications) ertification requirements N Inter-Partition ommunication mechanism Usage : Data Fusion, Triple Modular Redundancy Issues : Natively not supported by ARIN Non-Propagation Non disturbance of non-faulty partitions by faulty partitions (i.e. port overflow, message loss) Message Identification Ability to identify the origin of each message Page

3 Introduction & Issues The Periodic Delayed Protocol (PDP) Objectives : Deterministic N mechanism Message consumption order known Execution time & memory overheads minimized (e.g. No locks) Tight estimation of sufficient memory space ommunication Model Periodic task set One message produced per job Message available at the sender s job deadline PDP available next receiver s job Messages ordered with jobs deadlines ommunication Mechanism Wait-free shared circular queue (aka. PDP buffer) One pre-defined slot per message Message Identification One pre-defined message per slot Non-Propagation Page 3

4 Introduction & Issues PDP - Example Nothing to read Nothing to read Task A B R P D New job of R Key: A Deadline of A B A R B A R B A B R A B A B A A B A B A B A B A B R B R a b b c a b3 a3 b4 c a4 b a b6 c3 R PDP can Available consume PDP buffer Page 4

5 Introduction & Issues PDP - Example Task A B R Key: P D A Deadline of A New job of R B a b b c a b3 a3 b4 c a4 b a b6 c3 PDP Outdated PDP Available PDP buffer Page

6 Introduction & Issues PDP adaptation to partitioned systems Inter-Partition ommunication example Activated Activated Activated I) Implementation issue Space & time segregation PDP : for shared memory systems PDP : direct transfer to the receiver queue II) Design issue How do we deal with disjoint memory? How do we allow the PDP semantic How do we maintain the Non-Propagation & Message Identification properties Activated ontext switch ontext switch P P P3 Time Page 6

PDP 4PS : For Partitioned Systems General Methodology Message onditioning Before Transfer Store msg in sender memory space Prevent from msg overproduction Non-Propagation Provide sender IDs to msg

7 PDP 4PS : For Partitioned Systems General Methodology Message onditioning Before Transfer Store msg in sender memory space Prevent from msg overproduction Non-Propagation Provide sender IDs to msg Message Identification General architecture Message Actual Transfer Done before next receiver activation Message onditioning After Transfer Store msg in receiver memory space Insert msg in the RPB Non-Propagation Message Identification Page 7

8 PDP 4PS 4PS For Partitioned Systems Features: Role separation (DO-97) XML configuration Two architectures:. For platform suppliers Native implementation Wait-free access protocol. For application suppliers Reduce maintenance effort Page 8

By the Partitioning Kernel Execute at receiver partition activation Transfer only PDP available msg Statically determined Message

9 PDP 4PS : For Platform Supplier Methodology Message onditioning Before Transfer Store msg in EPB under PDP policy heck slot state before insertion No overproduction Non-Propagation Platform supplier architecture Reception Emission by senders receiver Message Actual Transfer By the Partitioning Kernel Execute at receiver partition activation Transfer only PDP available msg Statically determined Message Identification Message onditioning After Transfer Insert the msg in the RPB by the Partitioning Kernel Transfer and insertion by Partitioning Kernel Page 9

10 PDP 4PS : For Platform Supplier An example Task A B R P D Partition P (RMS) P P3 Task A, B R Nothing to flush Flush P P P3 P P P3 P P Idle P Idle B A R B A B A R B A B A B A PDP Available PDP Available EPB a b b a b3 a3 b4 a4 b a b6 c c c3 P EPB P a b b c a b3 RPB R can consume Page 0

11 PDP 4PS : For Platform Supplier An example Task A B R Partition Task New job of R P D P (RMS) P P3 A, B R Flush P P P3 P P P3 P P Idle P Idle B A R B A B A R B A B A B A PDP Available PDP Available EPB a3 b4 a4 b a b6 a6 b7 c c3 P c4 EPB P a b b c a b3 a3 b4 c a4 b a b6 c3 RPB PDP Outdated R can consume Page

PDP 4PS : For Application Supplier Methodology Message onditioning Before Transfer Store msg in Partitioning Kernel sending port Maintain the number

12 PDP 4PS : For Application Supplier Methodology Message onditioning Before Transfer Store msg in Partitioning Kernel sending port Maintain the number of sent msg by job No overproduction Non-Propagation Application Supplier architecture Insertion Emission and reception by senders by receiver Message Actual Transfer Partitioning Kernel original transfer policy (e.g. FIFO) Done before next receiver activation Message onditioning After Transfer Store msg in Partitioning Kernel receiving ports Message Identification Insert the msg in the RPB by the receiver Transfer by Partitioning Kernel Page

13 onclusion N Inter-Partition ommunication mechanism Main properties - Periodic task set - Specific communication model - Deterministic message delivery order - Non-Propagation and Message Identification properties Two architectures - For Platform supplier : wait-free - For Application supplier Experimented on POK (Partitioned Open Kernel) Further works Model transformation to produce kernel or application configuration Adaptation to direct memory accesses Page 3

14 Thank you Page 4

POK. An ARINC653-compliant operating system released under the BSD licence. Julien Delange, European Space Agency

POK. An ARINC653-compliant operating system released under the BSD licence. Julien Delange, European Space Agency POK An ARINC653-compliant operating system released under the BSD licence Julien Delange, European Space Agency Laurent Lec, MakeMeReach Introduction Problems