Tornado 2 2 and VxWorks 5 5

8/2/2019 Tornado 2 2 and VxWorks 5 5

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Tornado and VxWorks


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Copyright Wind River Systems, Inc. 2

Tornado-VxWorks ArchitectureThe Real-Time, Multitasking OS

Intertask Synchronization and Communication

The Project Facility

The Debugging Tools

The Networking Stack

Tornado and VxWorks


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What is Tornado?

Real-Time,

MultitaskingOS

Development and

Debugging

Tools

Networking


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Tornado Architecture - HW Target

The tools, registry, and target server can run on differenthosts

VxWorks

Target Agent

Tool

Tool

Tool

Host Target

Target

Server

Registry


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Tornado Architecture - Simulator Target

VxWorks runs as a process under the host OS

The simulator architecture provides no emulation ofinstruction, native compilers are used

Registry

Target

Server

VxWorks

Target Agent

Tool

Host

Tool

Tool


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Tornado ArchitectureThe Real-Time, Multitasking OS



The Debugging ToolsThe Networking Stack

Tornado and VxWorks


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What is a Task?

A task is a Kernel object dynamically created at runtime

Logical entity consisting of a Task Control Block (TCB) data structure andstack space

An independent thread of execution

A task is not a function However, a special purpose function (typically designed with an endless

loop) is used for the tasks entry point

Functions execute within the context of tasks

The VxWorks routine taskSpawn()invokes the entry point function foo

and gives the task its thread of liveness

foo()

{for (;;)

{waitForData( );/* Until external event occurs */processData( );}

}



Creating a Task



Multitasking

Separate tasks are created to perform different systemrequirements

For example, data acquisition and data computation

Each task alternates between ready and waiting A task manager (the multitasking kernel) is therefore required

VxWorks allows a task to wait for

A specified time delay (Delay)

An event such as an interrupt (Pend)



Task States



Multitasking Kernel

The wind kernel is that part of VxWorks which directlymanages tasks

It allocates the CPU to tasks according to the VxWorksscheduling algorithm

It uses Task Control Blocks (TCBs) to keep track of tasks One per task

Declared as WIND_TCBdata structure in taskLib.h

O.S. control information

state, task priority, delay timer,breakpoint list, error status,I/Oredirections

CPU Context Information

PC, SP, CPU registers, FPU registers



Kernel Operation

Scheduler



Multitasking Facilities







Tornado and VxWorks



Intertask synchronization

In a multitasking environment, facilities to achieve mutualsynchronization are needed

Producer-consumer architecture

Client-server architecture

In VxWorks, intertask synchronization is achieved using Binary Semaphores

Message Queues

Events

Pipes Some intertask synchronization facilities (queues and

pipes) also enable data transmission (intertaskcommunication)



Binary Semaphores

Binary semaphores exist in one of two states Full (synchronizing event has occurred)

Empty (synchronizing event has not occurred)

Intertask synchronization is obtained by creating anempty, binary semaphore for the synchronizing event

The task waiting for the event calls semTake( )and blocks untilthe semaphore is given

The task or interrupt service routine detecting the event callssemGive( ), which unblocks the waiting task



Message Queues

Message queues are kernel objects used for passinginformation between tasks

Message queues provide a FIFO buffer of messages

The task waiting for the synchronization message callsmsgQueueReceive( )and blocks until a message is onthe queue

The task sending the synchronization message callsmsgQueueSend( ), which unblocks a pending task

Task A Task B



Pipes

Pipes provide an alternative interface to the messagequeue facility in the VxWorks I/O system

Tasks block

When they read from an empty pipe, until data is available

When they write to a full pipe, until there is space available

Similar to their use of message queues, interrupt serviceroutines can write to a pipe, but cannot read from it



Events

VxWorks events are means of synchronization between Tasks and tasks

Interrupt service routines and tasks

VxWorks objects (binary semaphores and message queues) andtasks

Only tasks can receive events, whereas tasks, interruptservice routines or VxWorks objects can send events

Events are synchronous in nature

The receiving task pends while waiting for the events to be sent

Events allow a task to wait simultaneously on multipleresources

For example, events can be sent by semaphores, messagequeues and other tasks


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Mutual Exclusion Semaphores

Mutually exclusive access to shared resources isprovided in VxWorks by mutual-exclusion semaphores(mutexes)

VxWorks mutexes are designed to address issuesinherent to mutual exclusion, like

Priority inversion

Deletion safety

Recursive access to the shared resource

Semaphore ownership

Each critical section of the code has to be protected withmutexes, by having a task

Take the mutex before accessing the code

Give the mutex after having accessed it


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Counting Semaphores

Counting semaphores are similar to binary semaphores,except that they keep track of the number of times thesemaphore is given or taken

Every time the semaphore is given, the count is incremented

Every time the semaphore is taken, the count is decremented When the count reaches zero, a task that tries to take the

semaphore is blocked

Counting semaphores are useful for guarding multiplecopies of resources


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Signals

Signals asynchronously alter the control flow of a task An interrupt service routine or a task can send a signal to a task

The task which has received the signal will asynchronouslyexecute a signal handler

The signal handler executes in the receiving tasks context and

makes use of the tasks stack

If no signal handler is installed, the received signal is ignored

Since signals are asynchronous in nature, they are more

appropriate for error and exception handling than as ageneral-purpose intertask communication mechanism


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Tornado and VxWorks


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Projects

The project facility allows one to manage two projecttypes

Bootable projects

To configure and build a VxWorks image

Downloadable projects To build and download application modules to a running target

Projects can be grouped together in Workspaces

For each project more than one build specification can beused


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Bootable projects

Bootable projects are used to create a new, customizedVxWorks image

The system image consists of all desired system modules linkedtogether in a single, non-relocatable object module with nounresolved external references

The image can be customized by adding or removing VxWorkscomponents from the Workspace GUI

A bootable project is created specifying

A BSP

A toolchain (GNU or Diab)


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Downloadable Projects

Downloadable projects are used to create relocatableobject modules that can be downloaded and dynamicallylinked to VxWorks

Module downloading and dynamic linking is performed by theTarget Server, which maintains a host-resident targets symboltable

Downloadable projects

Are created by specifying a toolchain

GNU or Diab

Allow on the fly development

Modules can iteratively be downloaded, tested and debuggedwithout rebooting the target system


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Project Facility Workspace Window

3 Workspace window views


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Tornado-VxWorks Architecture

The Real-Time, Multitasking OS




Tornado and VxWorks


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Host-Resident Debugging Tools

WindShell Command Shell Provides command-line based, interactive access to all run-time

facilities

Browser

System-object viewer, graphical companion to WindShell CrossWind Debugger

Remote source-level debugger

Extended version of the GNU source-level debugger (GDB)

WindView Software Logical Analyzer Dynamic visualization tool


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WindShell

WindShell allows one to Access all VxWorks facilities by allowing calls to any VxWorks

routines

For example,

Spawning tasks

Creating VxWorks objects like semaphores, messagequeues, and pipes

Download object modules to the target system

Perform assembly-level debugging

Create and examine variables symbolically

Examine and modify memory


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WindShell


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Browser

The browser monitors the state of a target It shows detailed information on

Tasks

VxWorks objects (semaphores, message queues, ...)

Stack usage by all task on the target

Target CPU usage by task

Object-module structure and symbols

Interrupt vectors

The displays are snapshots, which can be updatedinteractively

Alternatively, the Browser can be configured to automaticallyupdate its display at specified intervals


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Browser


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CrossWind

CrossWind is a source level, graphical, debugging front-end using an enhanced version of GDB as its debuggingengine

It allows two debugging strategies

Task mode debugging

One task runs under debug control, while other tasks are notaffected

CrossWind can either

Attach to a running task, or

Start a new task under debugger control

System mode debugging

Whenever a task hits a breakpoint, the whole system stops

This is useful to debug tasks, interrupt service routines and pre-kernel execution


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CrossWind


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WindView 2.2

WindView allows one to study dynamic interactions of allthe elements of complex, real-time systems


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WindView 2.2

The WindView graph provides manageable access toimportant application information

WindView allows

Scrolling the information forward and backward in time

Zooming in/out Tailoring the display to only focus on the tasks and events of

interest

Setting locks on certain events and searching for their successiveoccurrences


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WindView 2.2 Example


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Problem Solving with WindView 2.2

WindView allows to Detect race conditions, deadlocks, CPU starvation and other

problems related to task interaction

Determine application responsiveness and performance

See cyclic patterns in application behavior

Conduct post-mortem analysis of failed systems

Detect memory leaks


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Tornado-VxWorks Architecture

The Real-Time, Multitasking OS




Tornado and VxWorks


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VxWorks Network Components

IP

TCP UDP

Socketszbuf

Shared MemoryNetwork

PPPEthernet

MUX

ftprshtelnetTargetserverNFS rlogin

netDrv

RPC

Application layer

Applicationprogramminginterface

Transport layer

Network layer

Link layer


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Shared-Memory Backplane Network

This allows multiple processors to communicate over theircommon backplane as if they were communicating over anetwork by using a standard network driver

host

vx3

Ethernet

Shared-MemoryNetwork

Backplane (e.g. VME, PCI)

vx2 vx1


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MUX The Network Driver Interface

This interface decouples the link layer and the networklayer

The network protocol does not need to be modified when addingnew network dirvers

A new network protocol can be added without modifying the

existing MUX-based network driver interfaces


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TCP/IP Protocol Suite

Based on the 4.4 BSD TCP/IP release, the TCP/IPprotocol suite comprises

UDP User Datagram Protocol

Low-overhead delivery mechanism of datagrams, used byseveral applications like BOOTP, DHCP, DNS, TFTP, ...

TCP Transmission Control Protocol Reliable, end-to-end transmission mechanism, used by Telnet,

Rlogin, FTP, ...

IP Internet Protocol

Hop-by-hop protocol to transmit datagrams

ICMP Internet Control Messagge Protocol Reports unexpected events in data transfer, used by ping

IGMP Internet Group Management Protocol

Used to support multicasting


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Sockets

Sockets allow processes to communicate within a singleCPU, across an Ethernet, across a backplane or acrossany connected combination of networks

VxWorks provides

BSD Sockets Datagram Sockets (UDP)

Stream Sockets (TCP)

Raw Sockets

Zbuf Sockets

An alternative set of sockets based on a data abstraction called

zbuf, zero-copy buffer

Applications can read and write BSD sockets without copyingdata between application buffers and network buffers


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Remote Access Applications

RSH Remote Command Execution Allows a VxWorks application to run commands on a remote

system and receive the command results on standard output anderror over socket connection

Only the client side implementation is provided

A server running on the remote system is assumed FTP File Transfer Protocol

Both client and server applications are provided

NFS Network File System

Server component

A target running VxWorks act as a file server for any systemthat runs an NFS client

Client component

A target running VxWorks can mount a remote file system


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Remote Access Applications (contd)

TFTP Trivial File Transfer Protocol Client and Server applications are provided

Unlike FTP or RSH, TFTP does not require any authentication

Rlogin Remote Login

On a VxWorks terminal, rlogin( )gives users the ability to log in to

remote systems on the network

The remote login daemon, rlogind(), allows remote users to login to VxWorks

Telnet

The server application only is provided

RPC Remote procedure call

RPC implements a client-server model of task interaction

A client requests a remote service from a server and waits for areply


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DNS and SNTP

DNS Domain Name System DNS is a distributed database used by TCP/IP applications that

maps hostnames to IP addresses

SNTP

Simple Network Time Protocol Client and server components are provided

The client is normally used to maintain its system internal clockaccuracy based on time values reported by one or moreservers

The server provides time information to other systems


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BOOTP Bootstrap Protocol

The BOOTP server Retrieves boot information from the Bootp Database (bootptab)

Supplies an Internet host with an IP address and relatedconfiguration information

The IP address is permanently assigned

The BOOTP client

Uses broadcasts to discover an appropriate server

Lets a target retrieve a set of boot parameters like an IP addressand a filename of the bootable image

Both client and server components are provided

BOOTP is implemented on top of UDP

DHCP Dynamic Host Configuration


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DHCP Dynamic Host ConfigurationProtocol

Like BOOTP, DHCP allows the permanent allocation ofconfiguration parameters to specific clients

However, DHCP also supports the assignment of anetwork address for a finite lease period

VxWorks includes a DHCP client, server, and relay agent The client can retrieve one or more sets of configuration

parameters from either a DHCP or BOOTP server

The server can process both BOOTP and DHCP

messages The DHCP relay agent provides forwarding of DHCP and

BOOTP messages across subnet boundaries


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IP Routing

If the destination is directly connected to the sender (e.g.,a point-to-point link) or on a shared network (e.g.,Ethernet), then IP datagrams are sent directly to thedestination

Otherwise, the sender sends the IP datagrams to a default router,and lets the router deliver them to destination

Each router maintains a routing table, which is used todeliver the IP datagrams to either

A local IP address, for a direct route, or

The next-hop router IP address, for an indirect route


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Dynamic Routing Protocols

Dynamic routing occurs when routers talk to adjacentrouters, informing each other of what network each routeris connected to

Entries in the routing tables change dynamically as routes

change over time The Routing Information Protocol (RIP) is provided with

VxWorks

This is intended for small to medium-sized networks

The longest path must be less than 16 hops It uses a distance-vector protocol

It contains a vector of distances as the hop count

RIP version 1 and 2 are supported


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Summary

Tornados three components VxWorks, real-time, multitasking operating system

Priority-based, preemptive scheduling algorithm

Intertask synchronization and communication services

Project facility and debugging tools Bootable and downloadable projects

Networking

Connects hosts and targets during development anddebugging

TCP/IP stack

Rich set of network applications and protocols


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References

Manuals available either in the Tornado on-line help, orvia the Wind River Bookstore at:www.windriver.com/windsurf/bookstore

Tornado Users Guide

WindView Users Guide and Users Reference

VxWorks Programmers Guide

VxWorks OS Libraries

VxWorks Network Programmers Guide
http://www.windriver.com/windsurf/bookstore/ehttp://pid_2.0_ws_agenda.ppt/http://www.windriver.com/windsurf/bookstore/e

Tornado 2 2 and VxWorks 5 5

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