self healing operating system

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Introduction Terminology Error Detection Error recovery Error signaling Error confinement Error detection and recovery Sola

Self Healing Operating System

Neethu . T VRoll No: 32

S7 Computer Science and Engineering

Government Engineering College

Sreekrishnapuram Palakkad

November 25, 2010
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OVERVIEW

1

Introduction2 Terminology

3 Error Detection

4 Error recovery

5 Error signaling

6 Error confinement

7 Error detection and recovery

8 Solaris 10 OS

9 Future scope

10 Conclusion

11

Reference
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OVERVIEW

1

Introduction2 Terminology

3 Error Detection

4 Error recovery

5 Error signaling

6 Error confinement


8 Solaris 10 OS

9 Future scope

10 Conclusion

11

Reference


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Introduction

All applications are dependent on the OS

When the OS dies, all running applications are lostResilience to errors is an important requirement of modernoperating systemSelf healing enables systems to diagnose themselfs and react

to faults

I d i T i l E D i E E i li E fi E d i d S l
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OVERVIEW

1 Introduction

2 Terminology

3 Error Detection

4 Error recovery

5 Error signaling

6 Error confinement


8 Solaris 10 OS

9 Future scope

10 Conclusion

11

Reference

I t d ti T i l E D t ti E E i li E fi t E d t ti d S l


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Terminology

Fault-Defect or flaw in hardware or software

Error -Deviation from correct stateFailure - Inability to perform expected task



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OVERVIEW

1 Introduction

2 Terminology

3 Error Detection

4 Error recovery

5 Error signaling

6 Error confinement


8 Solaris 10 OS

9 Future scope

10 Conclusion

11

Reference



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Error Detection in Existing OSs

Custom Error Detection Code in OSs

Linux - Deadlock Detection, Soft Lockup Detection etc

Windows - Deadlock Detection etcHardware Memory Protection - MMU

Watchdog Timers - Linux, Windows etc

Software Memory Protection - SafeDrive, XFI

Periodic Consistency Checks - EROS



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OVERVIEW

1 Introduction

2 Terminology

3 Error Detection

4 Error recovery

5 Error signaling

6 Error confinement


8 Solaris 10 OS

9 Future scope

10 Conclusion

11

Reference



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Error recovery in Existing OSs

Linux -Recovery by terminating thread

Restart Failed Component

Windows Vista - Example: Video Card DriverMinix3ChorusLinux+NooksIBM z/OS

Hardware RedundancyReboot Entire System



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gy y g g y

OVERVIEW

1 Introduction

2 Terminology

3 Error Detection

4 Error recovery

5 Error signaling

6 Error confinement


8 Solaris 10 OS

9 Future scope

10 Conclusion

11

Reference



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gy y g g y

Error signaling

C++ exception handling is used for unified error signaling

Devoloper defined exceptionsProcessor exceptions

Benifits of mapping processor exceptions to languageexceptions

Local error recovery using c++ catch statementGeneric handlers for all type of exceptionsGeneric handlers that just print out an error message and haltthe system

Normal run-time performance overhead is negligible

Provide developers a flexible and powerful technique



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OVERVIEW

1 Introduction

2 Terminology

3 Error Detection

4 Error recovery

5 Error signaling

6 Error confinement


8 Solaris 10 OS9 Future scope

10 Conclusion

11 Reference



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Error confinement

Isolate Os components

Used by microkernal:L4,Minix3

Nooks:Device driver isolation in linux

Objects in Choices can be placed in separate memoryprotection domains

Implemented using wrappers which inherit from target Classes

Example Protected Objects: Serial Port Driver,FileSystem

Inodes, Timer Driver

Recovery can be targeted toward the effected component



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Choices protected components

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OVERVIEW

1 Introduction

2 Terminology

3 Error Detection

4 Error recovery

5 Error signaling

6 Error confinement



10 Conclusion

11 Reference

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Error detection and Recovery

Code Reloading

Component Micro-RebootsAutomatic Service Restarts

Watchdog-based Recovery

Process-level Recovery



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Code reloading

Fault: Corruption of OS code by software bugs or hardwarebit-flips (Single Event Upsets)

Proactive Recovery: Periodically checksum OS code and

reload corrupted pages from stable storageReactive Recovery: If undefined instruction exception israised, reload relevant OS page from stable storage

Simple fault-injection experiments show 89 % recovery

Example: ARM based microprocessor for mobile phoneincludes Run Time Integrity Checker(RTIC)

Also used in EROS



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Component micro-reboots

Error: Unhandled Exceptions in Components

Recovery: Similar to component restarts in existing systemsInvolves destroying and re-creating C++ object

After micro-reboot , internal state may be error free

Request is re-tried after micro-reboot



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Automatic service restarts

Error: Unhandled Exception in a Process

Recovery: Automatically restart process

Used when component level restarts fail or if error occursoutside components (framework code)

Fault injection experiments show 78.9% recovery for processdispatcher (idle thread)



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Watchdog-based recovery

Error: Lockups inside OS

Recovery: Terminate locked up thread or dispatch exception

Thread termination explored on Linux

An OS hardware watchdog works by setting a count downtimer to run

computer malfunctions the tickles stop and the watchdogeventually counts down to zero and does an automatic rebootof the computer.

Exceptions allow possible local recovery without anyinformation loss (in contrast with thread termination)

Lockup fault injection experiments about 70 % recovery



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process recovery

What to do when OS error recovery is not possible?

Last Resort

Ensure minimal working subsystems - disk, recovery code

Save individual process stateRestore processes after full reboot

Item Explored on Linux

Re-use code for process checkpointing/migration support

Can recovery from arbitrary OS corruption that does notaffect user process state



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OVERVIEW

1 Introduction

2 Terminology

3 Error Detection

4 Error recovery

5 Error signaling

6 Error confinement



10 Conclusion

11 Reference



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solaris 10 OS

Introduce new architecture for buildingand deploying systems and servicescapable of predictive self healing

Solaris fault manager and solaris service

manager are two main components ofpredictive self heling

Fault manager receives hardware andsoftware errors and diagonose

automaticallyService manager provideservices,permitting automatic self healing

Services include start,stop,restart



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OVERVIEW

1 Introduction

2 Terminology

3 Error Detection

4 Error recovery

5 Error signaling

6 Error confinement



10 Conclusion

11 Reference



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Future scope

Working on OS restructuring to reduce error propagation and

prevent state loss during component micro-reboots

Framework for developer specified policies to governmicro-reboots and service restarts



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OVERVIEW

1 Introduction

2 Terminology

3 Error Detection

4 Error recovery

5 Error signaling

6 Error confinement



10 Conclusion

11 Reference



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Conclusion

Self-Healing Operating Systems may be built by incorporating

a variety of recovery techniques to address different faultmodels

It is also possible to detect and attempt recovery from systemhangs that would otherwise remain undetected.



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OVERVIEW

1 Introduction

2 Terminology

3 Error Detection

4 Error recovery

5 Error signaling

6 Error confinement



10 Conclusion

11 Reference



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Reference

1 ARM Integrator Family from the website

http://www.arm.com/miscPDFs/8877.pdf[visited onnovember 10]

2 P. M. Chen, W. T. Ng, S. Chandra, C. Aycock, G. Rajamani,and D. Lowell. The Rio File Cache: Surviving Operating

System Crashes. In Architectural Support for ProgrammingLanguages and Operating Systems, pages 74-83, 2004

3 Dijkstra, E.: Self-stabilizing systems in spite of distributedcontrol. Communications of the ACM,1974

4 M. Baker and M. Sullivan. The Recovery Box: Using Fast

Recovery to Provide High Availability in the UNIXEnvironment.In USENIX,pages 31-44, Summer 2005

5 Building a self heal operating systemhttp://choices.cs.uiuc.edu/selfhealing.pdf [visited on

november 6]



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THANK YOU
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