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Tornado and VxWorks. Copyright © Wind River Systems, Inc.2 Tornado-VxWorks Architecture The Real-Time, Multitasking OS Intertask Synchronization and Communication.

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Presentation on theme: "Tornado and VxWorks. Copyright © Wind River Systems, Inc.2 Tornado-VxWorks Architecture The Real-Time, Multitasking OS Intertask Synchronization and Communication."— Presentation transcript:

1 Tornado and VxWorks

2 Copyright © Wind River Systems, Inc.2 Tornado-VxWorks Architecture The Real-Time, Multitasking OS Intertask Synchronization and Communication The Project Facility The Debugging Tools The Networking Stack Tornado and VxWorks

3 Copyright © Wind River Systems, Inc.3 What is Tornado? Real-Time, Multitasking OS Development and Debugging Tools Networking

4 Copyright © Wind River Systems, Inc.4 Tornado Architecture - HW Target The tools, registry, and target server can run on different hosts VxWorks Target Agent Tool Host Target Server Registry

5 Copyright © Wind River Systems, Inc.5 Tornado Architecture - Simulator Target VxWorks runs as a process under the host OS The simulator architecture provides no emulation of instruction, native compilers are used Registry Target Server VxWorks Target Agent Tool Host Tool

6 Copyright © Wind River Systems, Inc.6 Tornado Architecture The Real-Time, Multitasking OS Intertask Synchronization and Communication The Project Facility The Debugging Tools The Networking Stack Tornado and VxWorks

7 Copyright © Wind River Systems, Inc.7 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 and stack 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 task’s entry point Functions execute within the context of tasks The VxWorks routine taskSpawn() invokes the entry point function foo and gives the task it’s thread of “liveness” foo() { for (;;) { waitForData( );/* Until external event occurs */ processData( ); } }

8 Copyright © Wind River Systems, Inc.8 Creating a Task

9 Copyright © Wind River Systems, Inc.9 Multitasking Separate tasks are created to perform different system requirements 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)

10 Copyright © Wind River Systems, Inc.10 Task States

11 Copyright © Wind River Systems, Inc.11 Multitasking Kernel The “wind” kernel is that part of VxWorks which directly manages tasks It allocates the CPU to tasks according to the VxWorks scheduling algorithm It uses Task Control Blocks (TCBs) to keep track of tasks One per task Declared as WIND_TCB data structure in taskLib.h O.S. control information – state, task priority, delay timer,breakpoint list, error status,I/O redirections CPU Context Information – PC, SP, CPU registers, FPU registers

12 Copyright © Wind River Systems, Inc.12 Kernel Operation Scheduler

13 Copyright © Wind River Systems, Inc.13 Multitasking Facilities

14 Copyright © Wind River Systems, Inc.14 Tornado-VxWorks Architecture The Real-Time, Multitasking OS Intertask Synchronization and Communication The Project Facility The Debugging Tools The Networking Stack Tornado and VxWorks

15 Copyright © Wind River Systems, Inc.15 Intertask synchronization In a multitasking environment, facilities to achieve mutual synchronization 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 (intertask communication)

16 Copyright © Wind River Systems, Inc.16 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 an empty, binary semaphore for the synchronizing event The task waiting for the event calls semTake( ) and blocks until the semaphore is given The task or interrupt service routine detecting the event calls semGive( ), which unblocks the waiting task

17 Copyright © Wind River Systems, Inc.17 Message Queues Message queues are kernel objects used for passing information between tasks Message queues provide a FIFO buffer of messages The task waiting for the synchronization message calls msgQueueReceive( ) and blocks until a message is on the queue The task sending the synchronization message calls msgQueueSend( ), which unblocks a pending task Task ATask B

18 Copyright © Wind River Systems, Inc.18 Pipes Pipes provide an alternative interface to the message queue 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 service routines can write to a pipe, but cannot read from it

19 Copyright © Wind River Systems, Inc.19 Events VxWorks events are means of synchronization between Tasks and tasks Interrupt service routines and tasks VxWorks objects (binary semaphores and message queues) and tasks Only tasks can receive events, whereas tasks, interrupt service 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 multiple resources For example, events can be sent by semaphores, message queues and other tasks

20 Copyright © Wind River Systems, Inc.20 Mutual Exclusion Semaphores Mutually exclusive access to shared resources is provided in VxWorks by mutual-exclusion semaphores (mutexes) VxWorks mutexes are designed to address issues inherent 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 with mutexes, by having a task Take the mutex before accessing the code Give the mutex after having accessed it

21 Copyright © Wind River Systems, Inc.21 Counting Semaphores Counting semaphores are similar to binary semaphores, except that they keep track of the number of times the semaphore 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 multiple copies of resources

22 Copyright © Wind River Systems, Inc.22 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 asynchronously execute a signal handler The signal handler executes in the receiving task’s context and makes use of the task’s 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 a general-purpose intertask communication mechanism

23 Copyright © Wind River Systems, Inc.23 Tornado-VxWorks Architecture The Real-Time, Multitasking OS Intertask Synchronization and Communication The Project Facility The Debugging Tools The Networking Stack Tornado and VxWorks

24 Copyright © Wind River Systems, Inc.24 Projects The project facility allows one to manage two project types 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 be used

25 Copyright © Wind River Systems, Inc.25 Bootable projects Bootable projects are used to create a new, customized VxWorks image The system image consists of all desired system modules linked together in a single, non-relocatable object module with no unresolved external references The image can be customized by adding or removing VxWorks components from the Workspace GUI A bootable project is created specifying A BSP A toolchain (GNU or Diab)

26 Copyright © Wind River Systems, Inc.26 Downloadable Projects Downloadable projects are used to create relocatable object modules that can be downloaded and dynamically linked to VxWorks Module downloading and dynamic linking is performed by the Target Server, which maintains a host-resident target’s symbol table Downloadable projects Are created by specifying a toolchain – GNU or Diab Allow “on the fly” development – Modules can iteratively be downloaded, tested and debugged without rebooting the target system

27 Copyright © Wind River Systems, Inc.27 Project Facility Workspace Window 3 Workspace window views

28 Copyright © Wind River Systems, Inc.28 Tornado-VxWorks Architecture The Real-Time, Multitasking OS Intertask Synchronization and Communication The Project Facility The Debugging Tools The Networking Stack Tornado and VxWorks

29 Copyright © Wind River Systems, Inc.29 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

30 Copyright © Wind River Systems, Inc.30 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, message queues, and pipes Download object modules to the target system Perform assembly-level debugging Create and examine variables symbolically Examine and modify memory

31 Copyright © Wind River Systems, Inc.31 WindShell

32 Copyright © Wind River Systems, Inc.32 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 updated interactively Alternatively, the Browser can be configured to automatically update its display at specified intervals

33 Copyright © Wind River Systems, Inc.33 Browser

34 Copyright © Wind River Systems, Inc.34 CrossWind CrossWind is a source level, graphical, debugging front- end using an enhanced version of GDB as its debugging engine It allows two debugging strategies Task mode debugging – One task runs under debug control, while other tasks are not affected – 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

35 Copyright © Wind River Systems, Inc.35 CrossWind

36 Copyright © Wind River Systems, Inc.36 WindView 2.2 WindView allows one to study dynamic interactions of all the elements of complex, real-time systems

37 Copyright © Wind River Systems, Inc.37 WindView 2.2 The WindView graph provides manageable access to important 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 successive occurrences

38 Copyright © Wind River Systems, Inc.38 WindView 2.2 Example

39 Copyright © Wind River Systems, Inc.39 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

40 Copyright © Wind River Systems, Inc.40 Tornado-VxWorks Architecture The Real-Time, Multitasking OS Intertask Synchronization and Communication The Project Facility The Debugging Tools The Networking Stack Tornado and VxWorks

41 Copyright © Wind River Systems, Inc.41 VxWorks Network Components IP TCPUDP Socketszbuf Shared Memory Network PPP Ethernet MUX ftp rsh telnet Target server NFS rlogin netDrv RPC Application layer Application programming interface Transport layer Network layer Link layer

42 Copyright © Wind River Systems, Inc.42 Shared-Memory Backplane Network This allows multiple processors to communicate over their common backplane as if they were communicating over a network by using a standard network driver host vx3 Ethernet Shared-Memory Network Backplane (e.g. VME, PCI) vx2vx1

43 Copyright © Wind River Systems, Inc.43 MUX – The Network Driver Interface This interface decouples the link layer and the network layer The network protocol does not need to be modified when adding new network dirvers A new network protocol can be added without modifying the existing MUX-based network driver interfaces

44 Copyright © Wind River Systems, Inc.44 TCP/IP Protocol Suite Based on the 4.4 BSD TCP/IP release, the TCP/IP protocol suite comprises UDP – User Datagram Protocol – Low-overhead delivery mechanism of datagrams, used by several 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

45 Copyright © Wind River Systems, Inc.45 Sockets Sockets allow processes to communicate within a single CPU, across an Ethernet, across a backplane or across any 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 copying data between application buffers and network buffers

46 Copyright © Wind River Systems, Inc.46 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 and error 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 system that runs an NFS client Client component – A target running VxWorks can mount a remote file system

47 Copyright © Wind River Systems, Inc.47 Remote Access Applications (cont’d) 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 log in 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 a reply

48 Copyright © Wind River Systems, Inc.48 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 clock accuracy based on time values reported by one or more servers – The server provides time information to other systems

49 Copyright © Wind River Systems, Inc.49 BOOTP – Bootstrap Protocol The BOOTP server Retrieves boot information from the Bootp Database (bootptab) Supplies an Internet host with an IP address and related configuration 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 address and a filename of the bootable image Both client and server components are provided BOOTP is implemented on top of UDP

50 Copyright © Wind River Systems, Inc.50 DHCP – Dynamic Host Configuration Protocol Like BOOTP, DHCP allows the permanent allocation of configuration parameters to specific clients However, DHCP also supports the assignment of a network 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

51 Copyright © Wind River Systems, Inc.51 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 the destination 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 to deliver the IP datagrams to either A local IP address, for a direct route, or The next-hop router IP address, for an indirect route

52 Copyright © Wind River Systems, Inc.52 Dynamic Routing Protocols Dynamic routing occurs when routers talk to adjacent routers, informing each other of what network each router is 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

53 Copyright © Wind River Systems, Inc.53 Summary Tornado’s 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 and debugging – TCP/IP stack – Rich set of network applications and protocols

54 Copyright © Wind River Systems, Inc.54 References Manuals available either in the Tornado on-line help, or via the Wind River Bookstore at: Tornado User’s Guide WindView User’s Guide and User’s Reference VxWorks Programmer’s Guide VxWorks OS Libraries VxWorks Network Programmer’s Guide


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