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Tornado and VxWorks

Tornado and VxWorks. Tornado and VxWorks. Tornado-VxWorks Architecture The Real-Time, Multitasking OS Intertask Synchronization and Communication The Project Facility The Debugging Tools The Networking Stack. What is Tornado?. Development and Debugging Tools. Real-Time,

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Tornado and VxWorks

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  1. Tornado and VxWorks

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

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

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

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

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

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

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

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

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

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

  17. Task A Task B 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 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 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 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 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 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 Copyright © Wind River Systems, Inc.

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

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

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

  31. WindShell 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 Copyright © Wind River Systems, Inc.

  33. Browser 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 Copyright © Wind River Systems, Inc.

  35. CrossWind 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 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 Copyright © Wind River Systems, Inc.

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

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

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

  42. vx3 vx2 vx1 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 Ethernet Shared-Memory Network Backplane (e.g. VME, PCI) 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 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 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 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 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 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 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 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 Copyright © Wind River Systems, Inc.

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