RTX 5.0 User s Guide. VenturCom, Inc. Five Cambridge Center Cambridge, MA Tel: Fax:

Transcription

1 RTX 5.0 User s Guide VenturCom, Inc. Five Cambridge Center Cambridge, MA Tel: Fax: info@vci.com

2 No part of this document may be reproduced or transmitted in any form or by any means, graphic, electronic, or mechanical, including photocopying, and recording or by any information storage or retrieval system without the prior written permission of VenturCom, Inc. unless such copying is expressly permitted by federal copyright law VenturCom, Inc. All rights reserved. While every effort has been made to ensure the accuracy and completeness of all information in this document, VenturCom, Inc. assumes no liability to any party for any loss or damage caused by errors or omissions or by statements of any kind in this document, its updates, supplements, or special editions, whether such errors, omissions, or statements result from negligence, accident, or any other cause. VenturCom, Inc. further assumes no liability arising out of the application or use of any product or system described herein; nor any liability for incidental or consequential damages arising from the use of this document. VenturCom, Inc. disclaims all warranties regarding the information contained herein, whether expressed, implied or statutory, including implied warranties of merchantability or fitness for a particular purpose. VenturCom, Inc. reserves the right to make changes to this document or to the products described herein without further notice. RTX is a trademark and CENTer is a servicemark of VenturCom, Inc. Microsoft, MS, and Win32 are registered trademarks and Windows, Windows CE, and Windows NT are trademarks of Microsoft Corporation. All other companies and product names may be trademarks or registered trademarks of their respective holders. RTX 5.0 User s Guide

3 Table of Contents WELCOME TO RTX IX Getting Support... ix Technical Support...ix VenturCom Web Site...ix Documentation Updates... x About the User s Guide... x CHAPTER 1 INTRODUCTION TO RTX... 1 The RTX Architecture... 1 Real-Time Inter-Process Communication...2 HAL Extension...2 Uniprocessor and Multiprocessor Systems...2 The RTX Application Programming Interface (API)... 3 Win32 and Real-Time API...3 RTX Executable Images...3 Run-Time Libraries...4 Unicode...4 Designing and Developing RTX Applications... 4 RTX Device Drivers...4 Testing Real-Time Applications...5 Creating and Starting an RTSS Process...5 Stopping an RTSS Process...5 CHAPTER 2 USING SOFTWARE DEVELOPMENT TOOLS... 7 Using the RTX Utilities... 8 Utility Task Table...8 RTSSrun Utility (Console and GUI)...9 RTSSrun GUI...10 RTSSkill Utility...11 RTSSview Utility...12 RTSSview Example...12 RTSS Object Viewer...13 RTSS Task Manager...15 RtxServer...16 Using the RTX AppWizard in Microsoft Visual Studio Creating a Project and Setting Options...17 Setting Project Options...18 Setting Program Options...19 Running an Image...20 Registering an RTDLL...21 iii

4 Using Microsoft Visual Studio Setting up Microsoft Visual Studio...21 Building and Running Images (Win32 Environment)...21 Building and Running Images (RTSS Environment)...22 Building and Registering RTDLLs...23 Creating RTX Dynamic Link Libraries Building an RTDLL...25 Building an RTSS DLL...25 Debugging an RTX Program Excluding debugging information...26 Using Microsoft s WinDbg 5.0 with RTSS...29 Testing an RTX Program with Shutdown Handlers Shutdown Program...29 Gencrash Driver...29 Usage...30 Using the RTX Properties Contol Panel CHAPTER 3 USING THE RTX FUNCTIONALITY Process and Thread Management Processes and Threads...34 Using Processes...34 Using Threads...35 Thread Priorities...35 System Memory Management...37 System Memory Allocation...37 System Memory Locking...38 Clocks and Timers...40 Clock Services...40 Timer Services...41 Sleep Services...42 APIs...42 Programming Considerations...42 Programming Example (RTX Timer and Sleep Calls)...42 Inter-Process Communication Object Names...43 Shared Memory...43 Inter-Process Communication via Shared Memory...43 Environments...44 Semaphores...44 Inter-Process Communication via Semaphores...45 Environments...45 Event Objects...46 Using RtCreateEvent...46 Using RtPulseEvent...46 iv

5 Mutex Objects...46 Ownership...46 Inter-Process Communication via Mutex Objects...47 Environments...47 Device Management Interrupts...48 Interrupt Management...48 APIs...48 General Programming Considerations...49 Win32 Environment Programming Considerations...49 Using RtAttachInterruptVector...49 Using RtAttachInterruptVectorEx...49 Using RtReleaseInterruptVector...50 Programming Example (Interrupt Management and Port I/O Calls)...50 Port IO...50 Port I/O Control APIs...50 Port I/O Data Transfer APIs...51 General Programming Considerations...51 Programming Example...51 Physical Memory Mapping...51 APIs...51 General Programming Considerations...52 Win32 Environment Programming Considerations...52 Programming Example (RTX Memory Mapping Calls)...52 Contiguous Memory Mapping...52 Programming Considerations...52 Programming Example (RTX Contiguous Memory Allocation Calls)...53 Bus IO...53 Programming Example (Bus I/O)...53 File IO...53 File IO...53 CHAPTER 4 DEVELOPING AN APPLICATION Using the RTX Makefile Variables...56 Sample Makefile...56 Using RTX Dynamic Link Libraries About RTSS DLLs and RTDLLs...57 C Run-Time Libraries: Programming Considerations for DLLs...57 RTSS DLLs...58 RTDLLs...58 RTSS DLL and RTDLL Code Examples...58 Using the C Run-time Library Functions Using Floating Point Enabling Floating-Point Support in RTSS Programs...59 v

6 Running RTSS Programs Using Floating-Point...59 Writing RTSS Device Drivers C++ and Structured Exception Handling C++ Support...60 Structured Exception Handling...60 Using SEH...61 Differences Between Win32 and RTSS Exception Handling...61 UnhandledExceptionFilter...61 Exception caused by a thread...61 Nested exceptions and collided unwinds...61 Debugging...62 General User Notes for Exception Handling...62 System Exception Handling About System Exception Handling...62 RTX Handler...62 Tables of Exceptions...63 RTX Exception Codes...63 Intel Exception Codes...63 RTX Exception Handling...64 Freeze or Terminate Processing...64 Alert User...64 Generate Event Log Entries...65 About RTX and Windows NT / Windows 2000 Stop Messages...65 Interpreting Windows NT Blue Screen Stop Messages...66 Section 1 - Stop Message...66 Section 2 - Driver List...66 Section 3 - System Stack Dump...66 Section 4 - Communication...67 Interpreting Windows 2000 Stop Screens...68 Interpreting RTX Green Screen Stop Messages...69 Section 1 - RTSS-Specific Stop Message...69 Section 2 - HAL-Supplied Stop Message...70 Starvation Management...70 Watchdog Management...70 Setting the Starvation Time Out Period...71 RTX Power Management for Windows CHAPTER 5 PERFORMANCE OVERVIEW Causes and Management of Interrupt Latencies Software Causes...74 Hardware Causes...74 RTX Management of Interrupt Latencies...74 Reducing Your System s Latencies: Tools Overview SRTM (System Response Time Measurement) and RTX Demo...75 KSRTM (Kernel System Response Time Measurement)...75 vi

7 LTP (Latency Test Program)...75 Timer Latency Display...75 KSRTM versus SRTM...75 Using KSRTM (Kernel System Response Time Measurement) Using SRTM (System Response Time Measurement) Using RTX Demo (Graphical version of SRTM) Interpreting the Max Latency Plot...79 Interpreting the Histogram Plot...80 Using the Timer Latency Display Tool Interpreting the Histogram...81 Interpreting the Latency display...82 Using LTP (Latency Test Program) APPENDIX A CODE AND FILE EXAMPLES Bus IO Programming Example Interrupt Management and Port IO Calls Programming Example Makefile Sample Nmake Input File Example RTDLL Code Example RTDLL Part 1: samplertdll.c...92 RTDLL Part 2: usingrtdll.c...92 RTDLL Part 3: rtdll.mak...94 RTDLL Part 4: Register the rtdll...94 RTSS DLL Code Example RTSS DLL Part 1: dll.c...95 RTSS DLL Part 2: dll.def...95 RTSS DLL Part 3: dll-test.c...96 RTSS DLL Part 4: dll.mak...97 RTSS DLL Part 5: runtest.c...97 RTSS DLL Makefile Example RTSSkill Examples RTSSkill Example RTSSkill Example RTSSview Example RTX Contiguous Memory Allocation Calls Programming Example RTX Kernel Memory Locking Calls Programming Example RTX Locked Memory Allocation Calls Programming Example RTX Memory Mapping Calls Programming Example RTX Process Memory Locking Calls Programming Example vii

8 RTX Timer and Sleep Calls Programming Example INDEX viii

9 Welcome to RTX 5.0 Document ID: VenturCom, Inc. All rights reserved. Getting Support VenturCom s Real-time Extension (RTX) adds real-time capabilities to Windows NT and Windows 2000 that are unparalleled in the industry. It offers developers a rich and powerful real-time feature set all in a familiar Win32-compatible interface. It also provides tools and utilities for building and executing real-time programs, along with tools for measuring and fine tuning the performance of both hardware and software. In addition to using the real-time interfaces and tools provided by RTX, developers can continue to take advantage of the abundance of products available for Windows NT and Windows And, with the RTX inter-process communication features, the Win32 runtime environment works seamlessly with the RTX real-time subsystem enabling the integration of Win32 and real-time functionality. Experienced real-time developers will value the power of the RTX interface; we suggest that you refer to the topics in the RTX Overview for a more detailed description of RTX and a discussion of important design decisions that need to be made in order to fully take advantage of RTX features. VenturCom offers a number of support options for RTX users, including technical support and the VenturCom Web site. Note: If you are a customer who purchased direct support, you would have received a Support ID# in the letter that comes with the software. Please have this number available for reference when contacting VenturCom. Users who purchased their product through third parties should contact those parties directly with their questions. Technical Support For technical support related to installing and using RTX, VenturCom offers several channels of communication. You can: ΠΠCall technical support at between 9:00 AM and 6:00 PM (Eastern Time) your questions to support@vci.com ΠFax your questions to VenturCom Web Site The VenturCom Customer Support Web page is located at: ix

10 If you are a customer with a current support contract or a member of the Real-time and Embedded Partner Program, then you should bookmark to the Web page in the Technical Support Area located at: These pages provide electronic access to the latest product releases, documentation, and release notes. With a valid Support ID#, you can access the online problem report database to submit new issues, or to obtain the status of previously reported issues. Documentation Updates VenturCom is committed to providing you with the information you need to use our products. From time to time, we may provide documentation updates for our products. Check our CENTer page for updates. While visiting CENTer, check out the various white pages and presentations. CENTer also provides access to several newsgroups. You ll also find free utilities and extensions that you can download. About the User s Guide The RTX User s Guide describes the RTX product and explains how to use its features; it is intended for users who are familiar with developing applications in a Win32 environment. The following list introduces the chapters in this guide. RTX Overview Describes the RTX architecture, discusses how to design programs using RTX. Using Software Development Tools Explains how to use RTX programs, utilities, and tools to develop real-time applications. It also contains procedures for building applications and dynamic link libraries as well as procedures for debugging and testing your application. Using the RTX Functionality Presents the RTX functionality, discusses important realtime programming issues, and provides references to real-time code examples that illustrate the implementation of real-time programming techniques. Developing an Application Explains how to use dynamic link libraries, C run-time library functions, and floating point when developing an application. It also describes exception handling in the RTSS and Win32 environments and techniques for managing starvation conditions. Performance Discusses key real-time performance issues, such as latency metrics and timing factors, and provides programming approaches for ensuring good response times in your applications. It also explains how to use the RTX performance tools. x

11 CHAPTER 1 Introduction to RTX Today s real-time and embedded applications contain a broad range of functionality, such as GUI-based operator interfaces, communication with other information systems, and timecritical monitoring and control of equipment. For both developers and end users of these applications, Windows NT and Windows 2000 with their advanced features, range of supported hardware configurations, and availability of off-the-shelf add-on components are the the operating system platforms of choice. However, since their functionality was not targeted for "hard" real-time applications, the use of Windows NT and Windows 2000 are significantly restricted, and often prevented, for these applications. VenturCom's RTX product bridges this gap by adding "hard" real-time capabilities to both Windows NT and Windows By extending the Windows NT and Windows 2000 operating systems, RTX enables application components or modules that require deterministic and high-speed response times, along with other non-real-time application components, to work together on a common Windows system. With RTX, you can use a single, low-cost platform to satisfy a full range of real-time and embedded application requirements. While RTX brings superior real-time capabilities to Windows NT and Windows 2000, there are two areas in which real-time application developers must take active responsibility to fully realize its benefits. First, because worst-case response times vary significantly among systems, developers and their end users must carefully select their systems. Different board vendors, especially video card vendors, make different tradeoffs between price, throughput, and deterministic behavior. With the help of VenturCom's RTX performance analysis tools, developers and their users can select systems that ensure their real-time requirements are met. Second, developers must properly implement RTX in their applications. RTX provides raw power that can, if implemented in applications improperly, adversely impact other Windows applications and might even compromise overall system stability. The User s Guide can assist you in implementing RTX. The RTX Architecture RTX adds a real-time subsystem, known as RTSS, to Windows NT and Windows 2000 (see the figure below). RTSS is conceptually similar to other Windows NT subsystems (such as Win32, POSIX, WOW, and DOS) in that it supports its own execution environment and API. RTSS differs in one important area, though: Instead of using the Windows NT or Windows 2000 scheduler, RTSS performs its own real-time thread scheduling. Furthermore, in a uniprocessor environment, all RTSS thread scheduling occurs ahead of all Windows scheduling, including Windows-managed interrupts and Deferred Procedure Calls (DPCs). 1

12 57;DQG:LQGRZV17:RUNLQJ7RJHWKHU Real-Time Inter-Process Communication RTSS also supports Inter-Process Communication (IPC) objects that can be manipulated by either RTSS or Win32 processes; this enables simple and standard communication and synchronization between real-time and non-real-time programs. Finally, RTSS provides other time-critical services such as clocks and timers and interrupt management to RTSS processes. HAL Extension RTX includes a real-time enabled Hardware Abstraction Layer (HAL) extension. This extension maintains interrupt isolation between RTSS and Windows NT or Windows Windows cannot mask (at the interrupt controller level) interrupts managed by RTSS. Windows interrupts are masked during RTSS processing. The real-time HAL extension supports high-resolution clocks and timers for RTSS, while it also supports non-real-time clocks and timers for Windows NT and Windows Other real-time HAL extension features include a software interrupt mechanism between RTSS and Windows; basic exception management; and various enhancements for determinism. Uniprocessor and Multiprocessor Systems RTX supports both uniprocessor and multiprocessor Windows NT and Windows 2000 systems. The run-time version of RTX, which supports multiprocessor systems, provides all of the features of the uniprocessor version, plus it exploits the features of Intel MPScompliant multiprocessor systems to provide improved performance in both Windows and RTX environments. Run-time RTX, for multiprocessor systems, implements a dedicated processor model. In this model, RTSS runs on one processor, while the remaining processors continue to run on Windows. The multiprocessor HAL acquires control of the last logical processor during the Windows boot sequence and it is reserved for RTSS. RTSS programs can then be loaded and 2

13 Chapter 1: Introduction executed on the dedicated processor. The RTX Application Programming Interface for Win32 and RTSS processes, including Floating-Point Unit (FPU) and structured exception handling, is used for both uniprocessor and multiprocessor systems. This eliminates the need to recode RTX (uniprocessor) applications for a multiprocessor platform. The RTX Application Programming Interface (API) The RTX API is based on the Win32 API, using the same API already familiar to Windows application developers. This approach allows developers to draw upon their Win32 experience, code base, and development tools, thus expediting hard real-time application development. Both Win32 and RTSS processes support the full RTX API albeit with different response times and performance characteristics allowing developers to effortlessly share or move code between environments. This topic discusses: Win32_and_Real-Time_API RTX_Executable_Images Run-Time_Libraries Unicode Win32 and Real-Time API RTX supports a subset of Win32 API functions, plus it provides a special set of real-time functions, known as RTAPI (Real-Time API). RTAPI functions are identified by an "Rt" prefix in their names. Some RTAPI functions are semantically identical to their Win32 counterparts, while others are unique to RTX (i.e., there are no similar Win32 calls). For example, RTAPI real-time IPC functions differ from Win32 IPC functions only in the IPC name space in which they operate and in the determinism possible with real-time IPC objects. On the other hand, the Win32 API does not include any functions related to interrupt management; therefore, unique interrupt management functions are defined in RTAPI. The RTX API was carefully selected to promote efficient development of real-time application components. RTX intentionally does not include Win32 functions, such as the GUI-related calls, that are normally used by the less time-critical components of an application. In fact, Win32 functions that are not essential to real-time programming, and impractical to implement with deterministic behavior, are not included in the RTX API. It is expected that most applications will consist of at least two processes working together-one Win32-based process (to take advantage of GUI and other Win32-only functions) and an RTSS-based process to perform time-critical processing. RTX Executable Images RTX provides three types of executable images: RTSS applications, RTSS DLLs, and RTDLLs. RTSS applications are the real-time analogues of Win32 applications. RTSS DLLs are RTSS applications that have been linked to provide an export library that RTSS and other applications can use to call functions within an RTSS DLL. RTSS DLLs are full RTSS processes and must be launched manually prior to their use by RTSS applications. RTDLLs 3

14 are passive code containers, similar in functionality to Win32 DLLs, which run in RTSS. For details about how to choose, design, and build appropriate combinations of these types of images, see the chapters Using Software Development Tools and Developing an Application in this guide. Run-Time Libraries Unicode RTX also supports various run-time libraries, and provides a C run-time library based on MS Visual C++. RTSS processes can be statically linked to include these libraries, provided they do not attempt to link to unsupported Win32 functions. RTSS processes can also be linked against specialized versions of dynamic link libraries (DLLs), which can be used to modularize real-time application code or provide run-time customization of real-time software environments. RTX supports Unicode applications. An RTSS process can use the wmain() function and accept wide character input arguments. Support for the WCS family of functions is included as part of the RTX-supported C run-time library. Designing and Developing RTX Applications To ensure successful development of a real-time application, designers and developers must carefully analyze how to efficiently partition the application. They must also establish the correct balance between non-real-time (Win32) processes and real-time (RTSS) processes and determine the interface between them. If, for example, there is time-critical processing in Win32 processes, too much non-time-critical processing in RTSS processes, or too much synchronization or data flow across the process interfaces, the application s performance, usability, and overall ease of development and maintenance will be jeopardized. An initial investment of time spent analyzing the various tradeoffs and designs in this critical architecture area will be worthwhile to both developers and their users. This topic discusses: ΠΠΠΠRTX_Device_Drivers Testing Real-Time Applications Starting an RTSS Process Stopping an RTSS Process RTX Device Drivers Some designs call for application components that act as device drivers to other application components, or board vendors may want to provide real-time device drivers for their boards that can be used by a variety of real-time and non-real-time applications. The device driver designer can use either DLLs or real-time IPC mechanisms to connect drivers and applications together. The real-time IPC offers the most flexible option because Win32 and RTSS processes can both access a common real-time driver using the same interface, even at the same time. The sample directory includes an RTX library for device drivers based on real-time IPC that provides a traditional device driver interface (e.g., open, close, read, write, 4

15 Chapter 1: Introduction and control) to either Win32 or RTSS applications. Testing Real-Time Applications In most cases, the initial development and testing of real-time application components, including device drivers, is most easily done in the Win32 environment. The Win32 environment provides the widest range of development, debug, and test tools, and the best detection of misbehaving applications. After all non-time-critical testing is completed, the real-time application component is simply re-linked as an RTSS process for final testing in the deterministic RTSS environment. If extensive debugging of RTSS processes is necessary, you can use Microsoft s WinDbg. Creating and Starting an RTSS Process Several methods are available for starting RTSS processes. During development and testing, you will typically start RTSS processes from the command prompt with optional command line arguments or by clicking on the RTSS executable file icon in Windows Explorer. For final applications, you will generally use either the feature that starts specified RTSS processes at boot time (i.e., when the "blue screen" starts), or you will launch RTSS processes directly from a Win32 process. To create and launch the RTSS process directly, you will use the Win32 RTCreateProcess call to ceate and start the specified RTSS process. Stopping an RTSS Process An RTSS process stops when: ΠΠΠThe process calls the ExitProcess function A user or a Win32 process runs the RTSSkill utility A user terminates the process through the RTSS Task Manager The process generates an exception A Windows NT or Windows 2000 system shutdown occurs (either a normal shutdown sequence or an exception-initiated Windows NT "blue screen" stop or Windows 2000 stop screen) RTSS processes can register shutdown handlers that are called when Windows is shut down or stopped to allow the final sequencing of equipment and cleanup prior to full system stop and possible reboot. 5

16 6

17 CHAPTER 2 Using Software Development Tools This chapter discusses the RTX programs, utilities, drivers, files, and RTX control panel settings that you work with when developing and testing your real-time programs. It contains procedures for using Microsoft Visual Studio, by itself or with the RTX AppWizard, for building RTSS images and dynamic link libraries. This chapter also contains instructions on debugging your programs using Microsoft s WinDbg and testing programs with shutdown handlers. This chapter contains information on: n Using the RTX Utilities Utility Task Table RTSSrun Utility RTSSkill Utility RTSSview Utility RTSS Task Manager RTSS Object Viewer RtxServer n Using the RTX AppWizard in Microsoft Visual Studio 6.0 n Using Microsoft Visual Studio 6.0 n n n n Creating Dynamic Link Libraries Debugging an RTX Program Testing an RTX Program with Shutdown Handlers Using the RTX Properties Contol Panel 7

18 Using the RTX Utilities Utility Task Table The table that follows shows which utility to use to perform a particular task.,i\rxzdqwwr 5XQDQ5766SURFHVV /RDGDQ5766' 5HJLVWHUDQ57' 7HUPLQDWHDQ5766SURFHVV 8QUHJLVWHUDQ57' 9LHZDOLVWRIDOOSURFHVVHVDQG UHJLVWHUHG57'V 9LHZLQIRUPDWLRQDERXW5766SURFHVVHV DQGWKHLUDVVRFLDWHGREMHFWVLQFOXGLQJ 7KUHDG7LPHU6HPDSKRUH0XWH[ 6KDUHGPHPRU\DQG/RDGHG57' 8VH 5766UXQFRQVROHRUIURPWKH57;6WDUW PHQX 5766UXQFRQVROHRUIURPWKH57;6WDUW PHQX 5766UXQFRQVROHRUIURPWKH57;6WDUW PHQX 5766NLOOFRQVROH RU 57667DVN0DQDJHURQWKH57;6WDUW PHQX 5766NLOOFRQVROH RU 57667DVN0DQDJHURQWKH57;6WDUW PHQX 5766NLOOFRQVROH RU 57667DVN0DQDJHURQWKH57;6WDUW PHQX 5766YLHZFRQVROH RU 57662EMHFW9LHZHURQWKH57;6WDUW PHQX 8

19 Chapter 2: Using Software Developmen Tools RTSSrun Utility (Console and GUI) Use the RTSSrun utility to run an RTSS process in the RTSS environment, load an RTSS DLL, and register an RTDLL. When you use RTSSrun to run an RTSS process, it scans the RTSS process service slots for a free slot. It copies the RTSS executable image to the target directory for the process slot and establishes a pointer to the path. It then copies the command line to the registry and starts the service for this RTSS process. If successful, the slot number of the new process is returned; otherwise, RTSSrun returns -1. RTSSrun Console Each time you use this utility with the /b or /d switch, the current version of the.rtss or.rtdll file is copied to a location in the %SystemRoot% directory. Thus, whenever you rebuild a boot-time RTSS application or an RTDLL, you must rerun RTSSrun in order to access the new version. Usage RTSSrun file [arguments] Format To run an RTSS process: RTSSrun [ /b ] <filename>[.rtss] [ arguments ] To register an RTDLL: RTSSrun /d [/s] <filename>[.rtdll] where /q = Disables messages indicating success or failure to start the RTSS process. /b = Runs the RTSS process early in the system boot sequence. /d = Loads an RTDLL and adds entries to the registry. /s = Allows an RTDLL to be loaded by several processes at the same time. Otherwise, only threads within a single process can simultaneously load a particular RTDLL. /t = Tests loading and unloading of RTDLLs. This switch must be used in conjunction with the /d switch. filename = Name of the file to be run. arguments = Command line arguments passed to the process. 9

20 RTSSrun GUI Usage On the VenturCom RTX SDK Start menu, choose RTSSRun. or On the RTSS Task Manager window, click the Start Task button. Results The RTSSrun window, shown below, opens. 5766UXQ:LQGRZ Special Mode Options Run RTSS process When running an RTSS process, you can elect to start the process early in the system boot sequence by selecting Register to run at boot time, however RTX must be set at boot time for this to take effect. Register RTDLL When registering an RTDLL, you can elect to: Share Between Processes Allows an RTDLL to be loaded by several processes at the same time. Otherwise, only threads within a single process can simultaneously load a particular RTDLL. Perform Load\Unload Test Performs test loading and unloading of RTDLLs. See Also RTSS Task Manager 10

21 Chapter 2: Using Software Developmen Tools RTSSkill Utility Use the RTSSkill utility to terminate a particular RTSS process or unregister an RTDLL that is not loaded. You cannot unregister an RTDLL if any RTSS process currently has it loaded. You can also use this utility to view a list of all RTSS processes, including registered RTDLLs that have not been loaded, by omitting the process number or filename. Usage To view processes and registered RTDLLs: RTSSkill To terminate process 001: RTSSkill 001 To unregister an ˆ DLL: RTSSkill myfile.rtdll Format To terminate a particular process: RTSSkill [/b] [process number] To unregister an RTDLL: RTSSkill filename.rtdll where /b = Undoes the RTSSrun /b action. The program will not start automatically at boot time. RTSSkill Examples See the RTSSkill Examples in Code and File Examples in Appendix A. 11

22 RTSSview Utility Use the RTSSview utility to view information about RTSS processes and their associated objects, such as events, semaphores, and loaded RTDLLs. Usage and Format RTSSview /A (provides internal system processes and WIN32 proxy processes Results RTSSview lists each type of RTSS object, followed by its memory address in the kernel address space and the process id. It also lists information specific to each particular object: Process Gives the name or type of process, followed beneath the listing by each thread object owned by that process. Thread Provides the priority and state of the thread, plus the value of the flag settings which indicate certain thread behaviors. RTX assigns a priority value to each thread in the user's process, with values ranging from 0 to 127 (see Thread Priorities on page 35). Threads that have negative priority numbers belong to system processes. The thread flags have the following assignments: 9DOXH [ [ [ [ [ [ 0HDQLQJ 'RQRWGHDOORFDWHPHPRU\ 'RQRWIUHHWKHWKUHDGVVWDFN 7KUHDGWHUPLQDWHG 7KUHDGFDQQRWEHUHVXPHG,QWHUUXSWWKUHDG )ORDWLQJSRLQW Timer Provides the clock number, the remaining time, and the timing interval. Semaphore Provides the count, maxcount, and the object name (if there is one). Mutex Lists the count, the address of the owner, and its object name (if there is one). Shared memory Gives the base memory address, the size of the shared memory, and the object name. RTDLL Lists the count, address of the owner, and the object name. Event Provides the state of the event, whether the event is reset manually or not, and the name of the event. File Provides the Windows NT handle for the file and the filename. RTSSview Example See the RTSSview Example in Code and File Examples in Appendix A. 12

23 Chapter 2: Using Software Developmen Tools RTSS Object Viewer When you start RTSS Object Viewer, it displays an explorer that allows you to navigate through all the active objects found in the Real-Time Subsystem (RTSS). The tree view (left panel) displays all active RTSS objects, while the list view (right panel) displays extended information on the items checked in the tree view. Usage On the VenturCom RTX SDK Start menu, choose RTSS Object Viewer. Results The RTSS Object Viewer window, shown below, opens EMHFW9LHZHU 13

24 Menu The RTSS Object Viewer window contains the following menus. For additional information, refer to the online help that is included in the application. File Provides standard exit option. Options Provides extra display options: Always On Top Keeps the RTSS Object Viewer window on top. Check All/Uncheck All Causes all object to be displayed/removed from the list view. View Lets you specify how the information is displayed: Refresh Now Refreshes the Explorer view. Refresh Rate Lets you specify a Refresh Rate of high (one second), normal (two seconds), low (five seconds), or Paused (turned off). The default is for automatic refresh to be turned off. Compact style Allows for a more condensed view of object attributes. Object attributes are displayed in one column instead of each attribute in its own column. Select Columns Allows you to select which columns to display and their order. This option is not available if Compact style is selected. Help Provides information about RTSS Object Viewer: Help Contents Opens the help contents. About RTSS Object Viewer Opens a pop-up with copyright information. 14

25 Chapter 2: Using Software Developmen Tools RTSS Task Manager RTSS Task Manager lets you view and control all active RTSS Processes and registered RTDLLs on your system. Usage On the VenturCom RTX SDK Start menu, choose RTSS Task Manager. Results The RTSS Task Manager window, shown below, opens DVN0DQDJHU Buttons and Options The RTSS Task Manager window contains the following buttons and options: Always On Top Keeps the RTSS Task Manager window on top. Start Task Starts up the RTSSrun graphical user interface. End Task Stops/unregisters the selected process or RTDLL. 15

26 RtxServer The RtxServer handles RTSS output and enables the user to view the output in the RtxServer output window and/or log the output to a file. The RtxServer is an RTX service that starts up at boot time if RTX is set to run at boot time or at runtime when an RTSS application is run or from the RTX control panel. Since the RtxServer is a service, it can not be started up by double clicking on its icon. The service can run in GUI mode or in non-gui mode. The GUI is brought up by default when the first printf or RtPrintf in an RTSS application is encountered. The GUI can also be manually brought up by double clicking on the RtxServer notification icon in the Taskbar s Status Area. The RtxServer notification icon is visible when the RtxServer is running and displays the state of the service and show error messages. Fatal error messages are are flagged with the notification icon and logged to the Event Viewer. The RtxServer allows for the storing and viewing of RTSS output through the screen and log file. When the GUI is exited, the display buffer is purged. Because logging is independent of the GUI, the logging will continue even if the GUI is exited. Some options for writing to the screen are saving the screen buffer to a file, clearing the display, changing screen buffer size and font settings of the output. You can also write to a log file, clear it, change its path, and put a banner containing RTX version information and start time in it. You can use append mode or clear mode for logging. See the online help for additional information on using RtxServer. 16

27 Chapter 2: Using Software Developmen Tools Using the RTX AppWizard in Microsoft Visual Studio 6.0 Use the RTX AppWizard in Microsoft Visual Studio 6.0 to create a project workspace for the development of RTX applications and dynamic link libraries. The RTX project workspace contains four configurations: Win32 Release, Win32 Debug, RTSS Release, and RTSS Debug. The wizard sets the Project Settings for each configuration according to the program and project options selected from its dialogs. It can also provide a basic C program framework with which to work. This program framework can include RTX program elements, which contain C code to create RTX objects and demonstrate their use. The topic explains how to: Create a project and set options using the RTX AppWizard and then build an image (Win32 or RTSS) or build a dynamic link library (RTDLL or Win32 DLL) Run an image ΠRegister an RTDLL Creating a Project and Setting Options Use the procedure that follows to create an RTX project using the RTXAppWizard in Microsoft Visual Studio. To create an RTX project 1. On the Visual Studio menu bar, select File New. 2. On the Projects tab, select RTX AppWizard from the list box. The New dialog box opens, as shown below. 57;$SS:L]DUG1HZ3URMHFWV'LDORJ%R[ 3. On the right side of the dialog, complete the following fields: Project name Enter the name of the project. Location Enter the directory in which to build the workspace. 17

28 Platforms Select the platform for which RTX AppWizard will build configurations (WCE emulation mode is not supported). 4. Click OK to save the settings. 5. Complete the steps of the RTX AppWizard by selecting the appropriate options in the RTX AppWizard dialog boxes. See the following instructions, Setting Project Options and Setting Program Options. Setting Project Options 57;$SS:L]DUG6WHSRI'LDORJ%R[ 1. The RTX AppWizard sets the Project Settings in each configuration for compiling and linking programs. Choose whether to build an RTX application (default) or a DLL by clicking the labeled radio buttons. 2. RTX supports either UNICODE (default) or ASCII string types in RTSS programs. Select which type of string format to use. 3. Some programs need support for C run-time functions. If your project needs this support, select either the single-threaded library or the multi-threaded library. If an RTDLL needs C run-time support, you must use the multi-threaded library. The default is no C run-time library support. 4. If these are all the options needed, click Finish. Otherwise, click Next to open the second dialog box, shown in the figure below. 18

29 Chapter 2: Using Software Developmen Tools Setting Program Options 57;$SS:L]DUG6WHSRI'LDORJ%R[ 1. The wizard can provide a basic C program framework by inserting some files into the project. The framework consists of a C source file that contains basic C construction calls and a C header file that contains #include and #define statements. The default is No program framework, just Set Project Setings. Select an option by clicking on the appropriate radio button. 2. RTX program elements can be included in the C program framework. These programming elements are code segments that create each RTX object and demonstrate its use. Areas in the element code that need to be customized by the user are indicated by "TO DO" comments. You can select more than one type of programming element for a single project. The default option is that no programming elements are to be included. 3. Click Back to return to the first dialog in order to modify or review selections. Otherwise, click Finish. The RTX AppWizard displays a New Project Information confirmation box, such as the one in the figure below, indicating the choices. 19

30 Running an Image 1HZ3URMHFW,QIRUPDWLRQ 4. Click OK. RTX AppWizard generates the RTX workspace and project according to the options you selected. After you have built your Win32 or RTSS image, you can run it from: n n A command prompt, Windows NT Explorer, or n Visual Studio (See the procedure that follows for special instructions on changing Visual Studio settings for RTSS Debug and Release images. You do not need to change any setting to run Win32 images.) To run an RTSS image in Visual Studio Use this procedure to run an RTSS image from within Visual Studio. Modify project settings for Win32 RTSS Release and Win32 RTSS Debug 1. Select Project Settings Debug tab. 2. In the Program Arguments field, copy the executable into the arguments section box and then add any other arguments. 3. Replace the text in Executable for debug session with: rtssrun.exe 4. Click OK to save the settings. Run the RTSS image 5. Choose Build Execute (or click the exclamation point on the toolbar). 20

31 Chapter 2: Using Software Developmen Tools Registering an RTDLL After you have built your RTDLL, you can register it using the RTSSrun utility. Using Microsoft Visual Studio 6.0 This topic explains how to: Set up Microsoft Visual Studio Build and run Win32 images Build and run RTSS images ΠBuild and register RTDLLs Note: The RTX AppWizard utility provides an easy-to-use alternate for creating a project workspace for the development of RTX applications and dynamic link libraries Note: Some projects created for Microsoft Developer Studio 5.0 will have /GZ specified as a compiler option. This option is incompatible with RTSS and Microsoft Visual Studio 6.0. Simply remove this option from your project settings in order to migrate a Developer Studio 5.0 project to a Visual Studio 6.0 project. All the link options described in this topic for Visual Studio 6.0 are appropriate for Developer Studio 5.0 as well. Setting up Microsoft Visual Studio Use the procedure that follows to direct Microsoft Visual Studio to the RTX include and libraries files. To set up Microsoft Visual Studio 1. On the Visual Studio Tools menu, choose Options and then choose the Directories tab. 2. In the Show Directories For box, select the following file types and enter their paths in the Directories box. The following assumes that it was installed with the default paths. If you changed the default path during installation, specify that path below. Include files c:\program files\vci\rtxsdk\include Library files c:\program files\vci\rtxsdk\lib 3. Click OK to save the settings. Building and Running Images (Win32 Environment) Use the procedures that follow to build and run a Win32 image. To build a Win32 image Create a new RTX Win32 project workspace 1. On the File menu, choose New and then choose the Projects tab. 2. Choose Win32 Console Application, enter a name, and then click OK. Specify the project settings 21

32 3. On the Project menu, choose Settings to open the Project Settings dialog box. 4. In the Settings For box, select All Configurations. 5. On the Link tab, add this library to Object/Library Modules: rtapi_w32.lib 6. Click OK to save the settings. To run a Win32 image After you have built your Win32 image, you can run it from: A command prompt, Windows NT Explorer, or Œ Visual Studio (you do not need to change any settings). Building and Running Images (RTSS Environment) Use the procedures that follow to build and run an RTSS image. To build an RTSS image Create a new RTX RTSS project workspace 1. On the File menu, choose New and then choose the Projects tab. 2. Select Win32 Console Application, enter a name, and then click OK. Specify the project settings 3. On the Project menu, choose Settings to open the Project Settings dialog box. 4. In the Settings For box, select either Win32Release or Win32Debug based on the version you are building. 5. On the Link tab, delete all Project Options and replace them with one of the following option sets. 1RÃ&Ã5XQ7LPHÃ6XSSRUWÃ5HOHDVH Versionrtapi_rtss.lib rtx_rtss.lib /NODEFAULTLIB /INCREMENTAL:NO /PDB:NONE /NOLOGO /driver /align:0x20 /subsystem:native,4.00 /RELEASE /entry:_rtapiprocessentry@8 Ã1RÃ&Ã5XQ7LPHÃ6XSSRUWÃ'HEXJ Versionrtapi_rtss.lib rtx_rtss.lib /NODEFAULTLIB /INCREMENTAL:NO /PDB:NONE /NOLOGO /driver /align:0x20 /subsystem:native,4.00 /debug:notmapped /debugtype:both /entry:_rtapiprocessentry@8 Ã6LQJOH7KUHDGHGÃ&Ã5XQ7LPHÃ6XSSRUWÃ5HOHDVHÃ9HUVLRQ startupcrt.obj RTXlibc.lib oldnames.lib rtapi_rtss.lib rtx_rtss.lib w32_dll.lib /NODEFAULTLIB /INCREMENTAL:NO /PDB:NONE /NOLOGO /driver /align:0x20 /subsystem:native,4.00 /RELEASE /entry:_rtapiprocessentrycrt@8 Ã6LQJOH7KUHDGHGÃ&Ã5XQ7LPHÃ6XSSRUWÃ'HEXJÃ9HUVLRQ startupcrt.obj RTXlibc.lib oldnames.lib rtapi_rtss.lib rtx_rtss.lib w32_dll.lib /NODEFAULTLIB /INCREMENTAL:NO /PDB:NONE /NOLOGO 22

33 Chapter 2: Using Software Developmen Tools /driver /align:0x20 /subsystem:native,4.00 /debug:notmapped /debugtype:both Ã0XOWL7KUHDGHGÃ&Ã5XQ7LPHÃ6XSSRUWÃ5HOHDVHÃ9HUVLRQ startupcrt.obj RTXlibcmt.lib oldnames.lib rtapi_rtss.lib rtx_rtss.lib w32_dll.lib /NODEFAULTLIB /INCREMENTAL:NO /PDB:NONE /NOLOGO /driver /align:0x20 /subsystem:native,4.00 /RELEASE Multi-Threaded C Run-Time Support: Debug Version startupcrt.obj RTXlibcmt.lib oldnames.lib rtapi_rtss.lib rtx_rtss.lib 32_dll.lib /NODEFAULTLIB /INCREMENTAL:NO /PDB:NONE /NOLOGO /driver /align:0x20 /subsystem:native,4.00 /debug:notmapped /debugtype:both /entry:_rtapiprocessentrycrt@8 6. Change the file extension in the Output File Name field from exe to rtss. 7. Click OK to save the settings. To run an RTSS image After you have built your RTSS image, you can run it from: A command prompt, Windows NT Explorer, or Œ Visual Studio (see the procedure that follows for instructions on changing Visual Studio settings). To run an RTSS image in Visual Studio Use the procedure that follows to run the image from within Visual Studio. Specify the project settings 1. On the Project menu, choose Settings to open the Project Settings dialog box, and then choose the Debug tab. 2. Complete the following fields: Settings For Select either Win32 Release or Win32 Debug, based on the version you plan to run. Executable for Debug Session Enter the path to RTSSrun.exe. For example: c:\program files\vci\rtx\bin\rtssrun.exe Program Arguments Enter the path to your.rtss image. For example: c:\program files\microsoft visual studio\myprojects\rtsstest\release\rtsstest.rtss 3. Click OK to save the settings. Run the RTSS image 4. On the Build menu, choose Execute RTSSrun.exe. Building and Registering RTDLLs Use the procedures that follow to build and register an RTDLL. To build an RTDLL Create a new project workspace 1. On the File menu, choose New and then choose the Projects tab. 23

34 2. Select Win32 Console Application, enter a name, and then click OK. Specify the project settings 3. On the Project menu, choose Settings to open the Project Settings dialog box. 4. In the Settings For box, select either Win32Release or Win32Debug, based on the version you are building. 5. On the Link tab, delete all Project Options and replace them with one of the following option sets. Project Options on the Link Tab for an RTDLL Ã1RÃ&Ã5XQ7LPHÃ6XSSRUWÃ5HOHDVHÃ9HUVLRQ rtapi_rtss.lib rtx_rtss.lib startupdll.obj /NODEFAULTLIB /INCREMENTAL:NO /PDB:NONE /NOLOGO /driver /align:0x20 /subsystem:native,4.00 /RELEASE /entry:_rtapidllentry@8 Ã1RÃ&Ã5XQ7LPHÃ6XSSRUWÃ'HEXJÃ9HUVLRQ rtapi_rtss.lib rtx_rtss.lib startupdll.obj /NODEFAULTLIB /INCREMENTAL:NO /PDB:NONE /NOLOGO /driver /align:0x20 /subsystem:native,4.00 /debug:notmapped /debugtype:both /entry:_rtapidllentry@8 Ã&Ã5XQ7LPHÃ6XSSRUWÃ5HOHDVHÃ9HUVLRQ ÃstartupDllCRT.obj RTXlibcmt.lib oldnames.lib rtapi_rtss.lib rtx_rtss.lib w32_dll.lib /NODEFAULTLIB /INCREMENTAL:NO /PDB:NONE /NOLOGO /driver /align:0x20 /subsystem:native,4.00 /RELEASE /entry:_rtapidllentrycrt@8 Ã&Ã5XQ7LPHÃ6XSSRUWÃ'HEXJÃ9HUVLRQ startupdllcrt.obj RTXlibcmt.lib oldnames.lib rtapi_rtss.lib rtx_rtss.lib w32_dll.lib /NODEFAULTLIB /INCREMENTAL:NO /PDB:NONE /NOLOGO /driver /align:0x20 /subsystem:native,4.00 /debug:notmapped /debugtype:both /entry:_rtapidllentrycrt@8 6. Change the file extension in the Output File Name field from exe to rtdll. 7. Click OK to save the settings. To register an RTDLL After you have built your RTDLL, you can register it using the RTSSrun utility: RTSSrun /d <filename>.[rtdll] [/s] For further details, see RTSSrun Utility on page 9. 24

35 Chapter 2: Using Software Developmen Tools Creating RTX Dynamic Link Libraries This topic explains how to: Build an RTDLL This type of real-time dynamic link library is an RTSS object which can be dynamically loaded and unloaded using the LoadLibrary and FreeLibrary calls. Build an RTSS DLL This type of real-time dynamic link library is an RTX process that can be loaded either at boot time or through a call to Windows NT or Windows 2000 from within a C/C++ program. For further details about the two types of real-time DLLs, see Using RTX Dynamic Link Libraries on page 57. Building an RTDLL There are two ways to build RTDLLs. You can create them through: Appropriate compile and link options in a Microsoft Visual Studio project. To build an RTDLL using this method, follow the applicable procedures in Using the RTX AppWizard in Microsoft Visual Studio 6.0 on page 17 or Using Microsoft Visual Studio 6.0 on page 21. ΠCommand line invocation of nmake using special rules. This method is illustrated below. Building an RTDLL through command line invocation The following is an example of an nmake input file which will build an RTDLL and Win32 DLL from a single source file, thandler.c.!include <rtx.mak> all: thandler.dll thankler.rtdll clean: -del thandler.obj thandler.dll thandler.rtdll Building an RTSS DLL You create an RTSS DLL with a 'main' entry point that performs any required initialization routines. The two required files are listed below (see the RTSS DLL Code Example in Code and File Examples in Appendix A for an example of each file). dll.c Defines the source call for the library dll.def Defines the DLL name and exported functions Once executed in the RTSS environment, RTSS programs can use the RTSS DLL. Note that the entry point into the RTSS DLL for starting the process is MAIN. RTSS DLL Makefile Example The following example shows a typical RTSS DLL makefile for dll.c. NODEBUG = 1!include <rtx.mak> 25

36 all: dll.rtss dll.rtss: dll.obj lib -nodefaultlib -machine:$(cpu) -out:dll.lib -def:dll.def dll.obj link $(rtsslflags) -out:dll.rtss dll.exp dll.obj $(rtsslibs) del dll.exp clean: -del *.rtss -del *.obj -del *.exe -del dll.lib Debugging an RTX Program Each makefile should include the master makefile, rtx.mak, which builds programs with full debugging information in a format compatible with Microsoft s WinDbg.exe. See the Makefile Sample in Code and File Examples in Appendix A. This topic explains how to: Exclude debugging information from a release version Use Microsoft s WinDbg 4.0 with RTSS ΠUse Microsoft s WinDbg 5.0 with RTSS Excluding debugging information You can exclude full debugging information from your release version by using the procedure that follows. To exclude debugging information from release version files At a command prompt, enter: Set NODEBUG=1 nmake -nologo -f MyProgram.mak or Add NODEBUG=1 to MyProgram.mak (as illustrated in the Makefile Sample for srtm.mak in Code and File Examples) Using Microsoft s WinDbg 4.0 with RTSS In order to debug using Microsoft s WinDbg 4.0, you need two systems: a host system on which to run WinDbg and a target system on which to run your driver. WinDbg 4.0 can debug Windows NT systems only. The procedures that follow show how to: Prepare the host and target systems for WinDbg Prepare the program for debugging Set up the WinDbg environment on the host system ΠStart the debug session 26

37 Chapter 2: Using Software Developmen Tools To prepare the host and target systems for WinDbg Connect the host system to the target system 1. Connect the two systems by inserting a null modem cable into the corresponding serial ports on each (COM1 or COM2). 2. Test the connection using an available serial communications package (such as terminal.exe) to ensure that data is transmitted and received on both sides. For more information on null modem cables and testing a serial connection, refer to the section on using a serial cable for kernel debugging in the Microsoft Windows NT DDK documentation. Set up the target system 3. Ensure that the target system has free builds of Windows NT and RTSS installed. If any of one of these is not installed on the target, install it according to its installation instructions. Modify the boot.ini file to enable kernel debugging 4. Change the attributes of boot.ini to permit editing. 5. Open the file in an editor and locate the line under the "[operating systems]" section that contains the operating system on which you run. Modify this line to contain one of the following lines of information: /DEBUG [ /BAUDRATE=<baud rate> ] /DEBUGPORT=<com port> [ /BAUDRATE=<baud rate> ] where com port = Serial port through which the host and target are connected. baud rate = Highest rate used by the machines. Note: Using /DEBUG assumes that the default serial port is COM2. Using /DEBUGPORT allows you to specify which serial port to use. If baud rate is not given, the system uses a default rate. For example, the line "multi (0) disk (0) rdisk (0) partition(1) \WINNT="Windows NT Version 4.00" /DEBUGPORT=COM2" /BAUDRATE=19200" sets the communications port to COM2 and the baud rate to For more information on using these switches, refer to the section on enabling kernel debugging on the target in the Microsoft Windows NT DDK documentation. 6. Save the file and exit the editor. 7. Reset the file attributes in boot.ini to their original states: > attrib +r +s +h boot.ini 8. Reboot the target system. To prepare the program for debugging 1. At the start of the source code, insert a hard break instruction: _asm int 3 2. To include debug information in the program, perform one of these steps: 3. In the program s makefile, comment the line NODEBUG=1 (if it is there). 4. At a command prompt, enter: Set NODEBUG= 5. Run NMAKE with your program s makefile to create an.rtss file. For example, the following line creates the file srtm.rtss: nmake -f srtm.mak 27

38 6. If the program was built on the host system, copy the.rtss file into a working directory on the target system. 7. Copy the symbol file (.rtss) to the %SystemRoot%\symbols directory on the host system. For example, at a command prompt, enter: >copy srtm.rtss c:\winnt\symbols 8. On the host system, ensure that the following files are in their correct locations. If they are not present, copy them from your RTX installation disks. 9. RTX debug information files in %SystemRoot%\symbols\ rtx_halext.dbg in SystemRoot%\symbols\ rtx_rtss.dbg in %SystemRoot%\symbols\ hal.dbg in %SystemRoot%\symbols\ To set up the WinDbg 4.0 environment on the host system 1. On the Start menu, choose Programs Win32 SDK Tools WinDbg. 2. On the File menu, open the program s source file. 3. On the View Options tab, set the following options. Workspace Tab Set the Logging option, if desired. Symbols Tab In the Symbol Search Path text box, enter the location of the.rtss file (this is required only if the file is not in the %SystemRoot%\symbols directory). In the Load Time box, select the Defer radio button. Kernel Debugger Tab Select the Enable Kernel Debugger check box. Under Communications, ensure that the values for Baud, Port, Cache, and Platform are correct. Debugger Tab Select the desired Radix and Registers settings and other desired options. This set of options is recommended: Ignore Case, Disconnect on Exit, Go on Thread Terminate, Debug Child Process, Verbose Output, and Abbreviated Context. 4. Click OK to save the options. To start the debug session 1. On the host Run menu, choose Go (or press F5). 2. On the target system, run the application. For example, at a command prompt, enter: > RTSSrun srtm The following message appears in the WinDbg command window. Thread Create: Process 0 Thread 0 Kernel debugger waiting to connect on baud Kernel Debugger connection established on baud Kernel Version 1381 Free 0x Module load: NT (symbols loaded) Hard coded breakpoint hit 3. At this point, the target system will not respond until WinDbg receives a "GO" command. Add breakpoints, as desired. 4. To continue the debugging session, choose Go on the Run menu (or press F5). Refer to the Microsoft WinDbg documentation for details on using WinDbg. 28

39 Chapter 2: Using Software Developmen Tools 5. To close the debugging session, cancel from the target system program and then exit from WinDbg on the host system. Using Microsoft s WinDbg 5.0 with RTSS Microsoft s WinDbg 5.0 can debug both Windows NT and Windows 2000 systems. In order to debug using Microsoft s WinDbg 5.0, you need to install WinDbg 5.0, i.e., the Windows 2000 debugger, on your host system. Your host and target systems can be either a Windows 2000 or Windows NT machine. The procedures for using WinDbg 5.0 with RTSS are the same as those described above for WinDbg 4.0. Testing an RTX Program with Shutdown Handlers This topic describes the: Sample shutdown program that you use to test an RTX program with shutdown handlers by forcing a Windows NT stop ΠGencrash driver which demonstrates RTSS shutdown management Shutdown Program Use the shutdown program to see a demonstration of RTSS shutdown handlers. You must first build this program using the RTX makefile. This program attaches a shutdown handler to a process and generates a continuous tone. If a Windows NT stop or system shutdown occurs during this time, then the shutdown handler prints out a message and sleeps for 10 seconds. The tone will then stop. Note: The message is visible only for unexpected NT stops (RT_SHUTDOWN_NT_STOP). For an orderly NT shutdown (RT_SHUTDOWN_NT_SYSTEM_SHUTDOWN), the message is not visible. Usage RTSSrun "c:\program files\vci\rtx\bin\samples\shutdown\shutdown" You can view the shutdown process or stop the shutdown program and its tone without shutting down Windows NT by using RTSSkill: 7RYLHZWKHVKXWGRZQ SURFHVV 7RNLOOWKHVKXWGRZQ SURFHVVQ 5766NLOO 5766NLOOQ Optionally, you can call the gencrash driver discussed next. Gencrash Driver Use the gencrash driver to see a demonstration of RTSS shutdown management. The gencrash driver provides a pop-up warning window and then bug checks (i.e., STOP 0) the Windows NT system to demonstrate RTSS shutdown management. 29

40 Usage net start gencrash Caution: Please close all applications before using gencrash. A FAT file system will generally require checking after a Windows NT stop. Using the RTX Properties Contol Panel You use the RTX Properties control panel to set configurable RTX registry parameters. It contains four tabs: About, Settings, Debug, and Control. To set RTX properties 1. In the system Control Panel, double-click the RTX Settings icon to open the RTX Properties control panel. 2. Specify the settings on each tab (see below) and then click Apply. 3. When finished, reboot your system to apply the change(s). About tab Displays RTX product and version information. Settings tab Startup Specifies whether RTX is started at system Boot, or Demand. If set to Demand, RTX does not start until an RTSS process is run. If set to Boot, you cannot start or stop RTX manually (see the Control tab section below). Starvation Time Out Controls the watchdog timer which monitors threads. If enabled, RTX stops the offending thread, issues a popup exception message, and then allows Windows NT to resume normal operation. See Starvation Management on page 70. Free Stack on Terminate Thread Controls whether RTSS frees the memory used for an RTSS thread's stack when the thread is terminated via TerminateThread. When selected, RTSS frees the memory. HAL Timer Period Controls the real-time HAL extension timer period. When using RtSetTimer and RtSetTimerRelative, the value must be a multiple of the HAL extension timer period. Time Quantum The value a thread will be given for its default time quantum. A value of 0 (zero) means run to completion. See RtSetThreadTimeQuantum and RtGetThreadTimeQuantum in the RTX 5.0 Reference Guide. RTSS Process Slots The number of RTSS process slots that can be run on your system. Minimum value is 10, maximum 999. Debug tab 30

41 Chapter 2: Using Software Developmen Tools Process Exception Disposition Controls the disposition of faulting RTSS processes. When Freeze the Faulting Process is selected, you can debug the process and then unload it using RTSSkill. Enter Kernel Debugger on RTSS Exception Controls whether the RTX exception handler initiates an interrupt to the debugger when a fault is raised. Caution: If selected when no debugger is available, RTX raises a double fault. Kernel Debugger Specifies which debugger is used, Microsoft's WinDbg or NuMega's SoftICE. See Debugging an RTX Program on page 26. Control tab Provides buttons for starting and stopping RTX. These are available only when the RTX Startup option (on the Settings tab) is set to Demand. 31

42 32

43 Chapter 3 Using the RTX Functionality This chapter presents the RTX functionality along with references to real-time code examples that demonstrate the use of RTX functions (calls) and illustrates the implementation of various real-time programming techniques. It also highlights key areas to consider, for both the RTSS and Win32 environments, while developing your programs. This chapter contains: n n n n Process and Thread Management Processes and Threads System Memory Management Clocks and Timers Interprocess Communication Object Names Shared Memory Semaphores Event Objects Mutex Objects Device Management Interrupts Port IO Physical Memory Mapping Contiguous Memory Mapping Bus IO File IO 33

44 Process and Thread Management Processes and Threads A process comprises an address space, object handles, and one or more paths of execution (threads). Threads are used, for example, to respond to interrupts and handle asynchronous process-related events in thread context. RTSS processes and threads function much like their Win32 counterparts. RTSS and Win32 processes and threads can access processes and threads only within their own environment. This topic discusses: Using_Processes Using_Threads ΠThread_Priorities Using Processes The sections that follow describe how processes run in the RTSS and Win32 environments. Processes in the RTSS Environment A process running in the RTSS environment consists of a set of handles to objects, process address space, at least one thread, and an executable. When a process is created, RTSS performs the following tasks: Loads the executable as a driver Allocates process heap from the non-paged pool ΠCreates the primary thread A process can be started by either one of these methods: Loading it as a device driver during system boot (using the RTSSrun /b utility) Running the RTSS executable from the command line ΠStarting the RTSS process from Win32 applications A process exits under one of these conditions: The last thread has exited One thread calls ExitProcess ΠThe process is killed with the RTSSkill utility or the RTSS Task Manager The maximum number of processes that can exist concurrently in the RTSS environment is equal to the number of RTSS process slots in the registry (the default is 10). Processes in the Win32 Environment A process running in the Win32 environment starts interacting with RTX when it makes an 34

45 Chapter 3: Using Using the RTX Functionality RTAPI call. RTX then may allocate resources for this process, alter its priorities, and perform other operations related to its Win32 process status. The number of Win32 processes that can interact with RTX is dynamic; it depends on your system s configuration and resources. Using Threads The CreateThread function creates either an RTSS or a Win32 thread, depending on the current execution environment of the process. You can specify the stack size of subsequently created threads of that process using CreateThread. The returned handle and thread ID are valid only in the CreateThread caller s environment. For instance, a Win32 process cannot manipulate the priority of an RTSS thread because the handle for the thread is valid only in the RTSS environment. You can, however, use the RTX Inter-Process Communication (IPC) mechanisms (such as mutex objects, semaphores, events, and shared memory) to synchronize and communicate between Win32 and RTSS processes and threads. Timer and Interrupt Objects Timer and interrupt objects derive from the threads; therefore, the handles for these objects are valid only in their own (Win32 or RTSS) environment. Similarly, these objects can be manipulated only by processes in their own environment. RTSS Environment An RTSS thread is the unit of execution in the RTSS environment. A ready-to-run RTSS thread is scheduled before all Windows NT and Windows 2000 threads. An RTSS thread runs until it gives up the CPU. A thread gives up the CPU when it: Waits for a synchronization object Lowers its own priority or raises another thread s priority Suspends itself Returns from the timer or interrupt handler (applicable to timer and interrupt threads) routines Calls Sleep with an argument of 0 Recevives a notification that a time quantum is set ΠIs interrupted by a higher priority The initial thread of a process has an 8 KB stack. Thread Priorities The sections that follow describe the priorities of threads in the RTSS and Win32 environments. RTSS Environment The RTSS environment has no distinct priority classes, so the threads of all RTSS processes compete for CPU using the thread priority only. An RTSS thread runs at one of 128 distinct priority levels. Threads execute in priority order and in "first in, first out" order within any single priority. If a time quantum is set to 0, the thread will run to completion. If the time quantum is set to another value, the thread will run for the specified time and then give up the CPU to another thread with the same priority. RTSS scheduling implements a priority inversion and deferred priority demotion mechanism to eliminate unbounded priority 35

46 inversion. For example, RTSS mutex objects support a level-one priority promoting mechanism. If a higher priority thread calls WFSO on a mutex object that is owned by a lower priority thread, the priority of the mutex owner is promoted to the same priority as the higher priority thread. An attempt to demote the priority of a mutex owner thread will be deferred until the thread releases the mutex. Win32 Environment A Win32 RTX program starts execution in the real-time priority class. RTX provides a mapping between RTSS and Win32 subsystem priorities. However, Win32 scheduling may exhibit unbounded priority inversion. Table 1, RTSS to Win32 Thread Priority Mapping, shows how RTSS symbolic priority names translate to requests for a particular Windows NT or Windows 2000 priority when RtSetThreadPriority is called by a Win32 program. Table 1. RTSS to Win32 Thread Priority Mapping 57666\PEROLF3ULRULW\ 1DPH DOXH :LQGRZV17:LQGRZV 6\PEROLF3ULRULW\1DPHIRU5HDO 7LPH3ULRULW\&ODVV 57B35,25,7<B0,1 7+5($'B35,25,7<B,'/( 57B35,25,7<B0,1 7+5($'B35,25,7<B/2:(67 57B35,25,7<B0,1 7+5($'B35,25,7<B%(/2:B1250$/ 57B35,25,7<B0,1 7+5($'B35,25,7<B1250$/ 57B35,25,7<B0,1 7+5($'B35,25,7<B$%29(B1250$/ 57B35,25,7<B0,1 7+5($'B35,25,7<B+,*+(67 57B35,25,7<B0$; 7+5($'B35,25,7<B7,0(B&5,7,&$/ Table 1 shows, for example, that RtSetThreadPriority(Thread, RT_PRIORITY_MIN+1) will result in a call to SetThreadPriority(Thread, THREAD_PRIORITY_LOWEST) by the Win32 version of the RTX interfaces. Any value from RT_PRIORITY_MIN+5 to RT_PRIORITY_MIN+126 will set the thread at THREAD_PRIORITY_HIGHEST and RT_PRIORITY_MAX will result in THREAD_PRIORITY_TIME_CRITICAL priority. These mappings are fixed and designed to preserve relative ordering among thread priorities. :LQ 9DOXH If a Win32 program calls RtGetThreadPriority, the real-time priority specified in the call to RtSetThreadPriority returns. There are some restrictions, however. The most likely source of confusion is when calls to RtSetThreadPriority and SetThreadPriority are mixed. The library may not always understand the RTSS priority when a duplicated thread handle is used, and it will return RT_PRIORITY_MIN+5 instead of RT_PRIORITY_MIN+6 through RT_PRIORITY_MIN+126. Threads that set and get their own RTSS priorities (such as specifying the thread with GetCurrentThread), will always get the RTSS priority that was set. Win32 programs should use the Rt priority calls for the Win32 thread to claim other than the lowest RTSS scheduling priority when waiting on an RTSS synchronization object. For instance, a Win32 thread with an RTSS priority of RT_PRIORITY_MAX will own a mutex 36

47 Chapter 3: Using Using the RTX Functionality before an RTSS thread waiting for the same mutex with a priority less than RT_PRIORITY_MAX. Table 2, Win32 to RTSS Thread Priority Mapping, shows what callers of the Win32 "set" and "get" thread priority calls should expect in the RTSS environment. This table describes the inverse of the mapping shown in Table 1. Table 2. Win32 to RTSS Thread Priority Mapping :LQGRZV17:LQGRZV 6\PEROLF3ULRULW\1DPHIRU5HDO 7LPH3ULRULW\&ODVV 9DOXH 57666\PEROLF 3ULRULW\1DPH 7+5($'B35,25,7<B,'/( 57B35,25,7<B0,1 7+5($'B35,25,7<B/2:(67 57B35,25,7<B0,1 7+5($'B35,25,7<B%(/2:B1250$/ 57B35,25,7<B0,1 7+5($'B35,25,7<B1250$/ 57B35,25,7<B0,1 7+5($'B35,25,7<B$%29(B1250$/ 57B35,25,7<B0,1 7+5($'B35,25,7<B+,*+(67 57B35,25,7<B0,1 7+5($'B35,25,7<B7,0(B&5,7,&$/ 57B35,25,7<B0$; 9DOXH There are no additional priorities between THREAD_PRIORITY_IDLE and THREAD_PRIORITY_HIGHEST. If you need finer grain priorities, you should use the RTSS priority spectrum instead. Just as in Win32, this value specifies a thread priority that is higher than all other priorities. Win32 Environment Programming Considerations WIn32 RTX program starts execution in the normal priority class, then calls the first RtGetThreadPriority, RtSetThreadPriority, or any other real-time priority function. This is the desired behavior for most applications because it gives the process the best possible real-time performance. This does, however, cause problems when the Win32 threads have GUI components. When a thread in the REALTIME_PRIORITY_CLASS interacts with the GUI side of Windows NT and Windows 2000, slowdowns and lock-ups occur. You can avoid this problem when writing a Win32 application that has a GUI component (and links to rtapi_win32.lib), by making sure that your program first makes this call: SetPriorityClass( GetCurrentProcess(), NORMAL_PRIORITY_CLASS) System Memory Management This topic discusses: System memory allocation ΠSystem memory locking System Memory Allocation A process frequently must allocate additional memory to perform its operations. The RTX memory allocation routine always allocates memory that is locked, thus eliminating any chance of latencies due to page faults. Memory Allocation APIs 37

48 The following APIs are available to access RTX system memory allocation services: RtAllocateLockedMemory allocates memory that is backed by physical memory and locked, then maps the memory into the virtual address space of the process. RtFreeLockedMemory frees a previously allocated locked memory region. RTSS and Win32 Programming Considerations Locked memory is always allocated from a non-paged pool of memory that is maintained by Windows NT and Windows This pool of memory is relatively small and is rapidly fragmented by the allocations of other drivers and subsystems in Windows NT and Windows 2000 shortly after system boot. To avoid failure of large allocations, you should minimize their use and/or ensure that they are accomplished shortly after system boot. Programming Example (RTX Locked Memory Allocation Calls) See the RTX Locked Memory Allocation Calls Programming Example in Code and File Examples in Appendix A. It demonstrates the use of RTX locked memory allocation calls. System Memory Locking To prevent page faults, and hence unpredictable delays in critical sections of code, real-time applications need to lock data and code in memory, including code and data in the operating system itself. Process Locking APIs The following APIs are available to access RTX process memory locking services: RtLockProcess locks all pageable sections of a process into physical memory. RtUnlockProcess unlocks sections of a process s virtual address space previously locked into physical memory. RtCommitLockProcessHeap commits and locks the process s heap. RtCommitLockHeap commits and locks the specified heap. RtCommitLockStack commits and locks the specified stack. RTSS Environment Programming Considerations By default, all process and memory objects in the RTSS environment are locked into physical memory to avoid page faults in RTSS processes. The Rt*Lock (Process, Heap, Stack) functions will always complete with success in the RTSS environment but will perform no actual operations. Win32 Environment Programming Considerations Unless explicitly locked into physical memory, all Windows NT and Windows 2000 processes and services are paged. In the Win32 environment, the RtLockProcess function should be utilized to prevent your real-time process from incurring page faults. 38

49 Chapter 3: Using Using the RTX Functionality Programming Example (RTX Process Memory Locking Calls) See the RTX Process Memory Locking Calls Programming Example in Code and File Examples in Appendix A. It demonstrates the use of RTX process memory locking calls. Kernel Locking APIs The following APIs are available to access RTX kernel memory locking services: RtLockKernel locks pageable sections of the Windows NT and Windows 2000 kernel into physical memory. RtUnlockKernel unlocks sections of the Windows NT and Wndows 2000 kernel previously locked into physical memory. RTSS Environment Programming Considerations By default, all processes and memory objects in the RTSS environment are locked into physical memory. Win32 Environment Programming Considerations Certain Windows NT operating system components are paged, including most of the kernel and the Win32 subsystem. In order to prevent delays of your real-time processes due to kernel page faults, use the RtLockKernel function. Windows` NT device drivers geneˆ ally do not page; device drivers loaded at boot time never page. In order to make drivers pageable by the system, the developer of that driver must carefully structure the driver and manually mark the code sections that are to be paged. Given the complexity, f w drivers are structuˆ d in this way. Locking the Windows NT or Windows 2000 kernel and processes reduces the pool of available physical memory. This can have a detrimental effect on the performance of nonreal-time system operations. Adequate memory should be included in any system to accommodate the desired performance of any non-real-time operations. For information on non-paged pool size, go the Microsoft Knowledge Base or MSDN Web site. Programming Example (RTX Kernel Memory Locking Calls) See the RTX Kernel Memory Locking Calls Programming Example in Code and File Examples in Appendix A. It demonstrates the use of RTX kernel memory locking calls. See Also Contiguous Memory Management 39

50 Clocks and Timers Real-time systems require a number of operating system timing services. The operating system must be able to keep an accurate accounting of the passage of time, schedule threads at precise times, and suspend threads for precise intervals. The RTX clock and timer facilities provide the services necessary for threads to perform periodic tasks that correspond with the external passage of time. This topic discusses: Clock services Timer services Œ Sleep services Clock Services The RTX clocks are counters of specified intervals that measure the passage of time. APIs The following APIs are available to access RTX clock services: RtGetClockTime delivers the current value of the specified clock. RtSetClockTime sets the value of the specified clock. RtGetClockResolution delivers the resolution of the specified clock. RtGetClockTimerPeriod delivers the minimum timer period for the specified clock. The clock values are delivered and set in 100ns units (ticks) and are reported as the number of ticks since 12:00 AM January 1, Clock Types The RTX clocks, available in the Win32 and RTSS environments, are: CLOCK_1 (alias CLOCK_SYSTEM) CLOCK_1 services are provided by the real-time HAL extension and have a resolution of 1 ms. Threads in both the Win32 and RTSS environments may schedule timers with periods in increments of ms on this clock. CLOCK_2 (alias CLOCK_FASTEST) CLOCK_2 services are provided by the real-time HAL extension and have a resolution of 1 µs. The period for timers scheduled on this clock is variable and can be set to 100, 200, 500, or 1000 µs. You can set the HAL extension timer period using the RTX Settings control panel. Relationship to Win32 Clocks The RTX clocks are updated by services provided in the real-time HAL extension. The RTX clocks are synchronized with the RTX timer services. However, the RTX clocks are not synchronized with either the Windows NT or Windows 2000 system clock or the batterybacked time-of-day clock. 40

51 Chapter 3: Using Using the RTX Functionality RTX and Windows NT / Windows 2000 Clock Accuracy (UP Systems Only) The interval timer hardware (8254 based) on standard PCs cannot be programmed to run at an even division of seconds (the fundamental interval period is nanoseconds). This means that the actual timer period is always somewhat different from the specified HAL extension timer period (the HalTimerPeriod setting in the registry). In addition, the interval timer is used to update the clock and every interval tick adds a fixed time increment to the clock. Windows NT and Windows 2000 maintain an internal time increment resolution of 0.1 microseconds, which leads to an accumulation of rounding errors and results in a small clock drift relative to the "true" time-of-day. Because of this drift, Windows NT and Windows 2000 periodically read the CMOS time-of-day clock on the PC and applies a drift correction. The RTX clock also has drift, but at a different rate from the Windows NT and Windows 2000 clocks. The RTX clock is designed to run at a rate that maintains synchronization with the specified timer period (that is, the timer is known to expire at fixed clock times). This allows a straightforward calculation of timer expiration values and timer response latencies. The table that follows provides the actual timer periods and associated clock drift rates for the each of the possible timer periods. Note: This does not apply to MP systems because they work on different processors. 6SHFLILHG7LPHU 3HULRG $FWXDO7LPHU3HULRG :LQGRZV17 :LQGRZV &ORFN'ULIW 57;&ORFN'ULIW General Programming Considerations: The RTX clock should not be used as a time-ofday clock, unless the application is aware of these drift issues. Timer Services An RTX Timer is an implicit handling thread that receives notification from RTSS of a timer expiration and calls the handling routine specified when the timer was created. Timers are associated with a clock in the system against which its expiration is measured when it is created. A timer begins to count down to its expiration after having been set. Once the timer has expired and the handling routine returns, the timer can be automatically rearmed. Timers that have their repeat interval set to zero execute their handling routine only once and are referred to as "one-shot" timers. Timers that have their repeat interval set to a valid value will execute their handling routine on an ongoing periodic basis and are referred to as "repeat" or "interval" timers. APIs The following APIs are available to access RTX timer services: RtCreateTimer creates a timer associated with a specified clock. 41

52 RtDeleteTimer deletes a previously created timer. RtCancelTimer cancels the expiration of the specified timer. RtSetTimer sets the absolute expiration time and repeat interval of the specified timer. RtSetTimerRelative sets the relative expiration time and repeat interval of the specified timer. Relationship to Windows NT Timers RTX timers are not synchronization objects which means threads cannot wait for single objects with an RTX timer handle. This is in contrast to the Windows NT waitable timer, which is an object on which a thread can wait, or against which a thread can receive notification. Win32 and RTSS Programming Considerations If your application needs to inform other threads of a timer expiration, you should use the appropriate notification object in the handling routine to indicate the event. Sleep Services The sleep services let you suspend the current thread for a specified period of time. APIs The following APIs are available to access RTX sleep services: Sleep suspends the current thread for the specified number of milliseconds. RtSleepFt suspends the current thread for the specified period of time in 100 nanosecond units. Programming Considerations RtSleepFt is not supported for use within a Win32 timer thread. The rounding policy on timer expirations including timers, wait functions, and sleep functions is to truncate the specified interval down to the timer tick count. If the count is zero, then the count is set to one. Programming Example (RTX Timer and Sleep Calls) See RTX Timer and Sleep Calls Programming Example in Code and File Examples in Appendix A. It demonstrates the use of RTX timer and sleep calls. 42

53 Chapter 3: Using Using the RTX Functionality Inter-Process Communication Object Names Named objects provide an easy way for processes to share object handles. The name specified by the creating process is limited to RTX_MAX_PATH characters, and can include any character except the backslash path-separator character (\). Once a process has created a named event, mutex, semaphore, or shared memory object, other processes can use the name to call the appropriate function (RtOpenEvent, RtOpenMutex, RtOpenSemaphore, or RtOpenSharedMemory) to open a handle to the object. Name comparison is case-sensitive. The names of event, mutex, semaphore, and shared-memory objects share the same name space. If you specify a name that is in use by an object of another type when creating an object, the function succeeds, but GetLastError returns ERROR_ALREADY_EXISTS. Therefore, when creating named objects, use unique names and be sure to check function return values for duplicate-name errors. For example, if the name specified in a call to RtCreateMutex matches the name of an existing mutex object, the function returns a handle of the existing object. In this case, the call to RtCreateMutex is equivalent to a call to RtOpenMutex. Having multiple processes use RtCreateMutex for the same mutex is therefore equivalent to having one process that calls RtCreateMutex while the other processes call RtOpenMutex, except that it eliminates the need to ensure that the creating process is started first. When using this technique for mutex objects, however, none of the calling processes should request immediate ownership of the mutex. If multiple processes do request immediate ownership, it can be difficult to predict which process actually gets the initial ownership. Shared Memory The RTSS shared memory object is a region of non-paged physical memory that can be mapped into the virtual address space of a process. When a shared memory object has a name, additional processes may map the region of memory. A shared memory object is accessed with both a handle and a virtual address. In order for a process to completely end its access to a shared memory object it must close the handle. When all processes end their access to a shared memory object, the following occur: The memory region is returned to the pool of non-paged kernel memory. ΠThe object ceases to exist. Inter-Process Communication via Shared Memory RTSS shared memory objects allow you to share blocks of data among multiple processes, including RTSS processes and Win32 processes. To do this, a thread in each process must have its own process-relative handle to a single RTSS shared memory object and its own process-relative pointer to a location where the virtual address of the mapping will be stored. These handles and pointers can be obtained by calling either RtCreateSharedMemory or RtOpenSharedMemory. Using RtCreateSharedMemory In order for several processes to use a shared memory object, the object must be first created 43

54 using RtCreateSharedMemory. Other processes can then use the shared memory object s given name to map the shared memory object. RtCreateSharedMemory returns a handle and sets a location to the base address of the shared memory. RtCreateSharedMemory fails if the amount of memory requested cannot be allocated or if the named shared memory object already exists. When RtCreateSharedMemory fails, no memory is mapped and no handles are returned. RtCreateSharedMemory does not default to RtOpenSharedMemory if a shared memory object of the same name already exists. Only one process can successfully create the shared memory object. Using RtOpenSharedMemory RtOpenSharedMemory maps an already created shared memory object. After the shared memory object has been created by a process, additional processes may map the shared memory into their address spaces by calling RtOpenSharedMemory. RtOpenSharedMemory will fail if the named shared memory object does not exist. RtOpenSharedMemory returns a handle to the shared memory object and sets a location to the base address of the shared memory. When a process is finished with the shared memory it should close the handle to the shared memory object. Environments The RTSS shared memory object is always maintained in the RTSS environment. However, Win32 processes may create and open RTSS shared memory objects. The RTSS shared memory object is its own named object. The RtCreateSharedMemory and RtOpenSharedMemory calls implicitly map the shared memory; this eliminates the explicit Win32 call to the MapViewOfFile call. When the shared memory object is created, RTSS backs the shared memory object with non-paged memory. Semaphores The RTSS semaphore object is a synchronization object that maintains a count between zero and a specified maximum value. The count is decreased by one each time a thread completes a wait for the semaphore object; the count is increased by a variable amount at the semaphore release. When the count reaches zero, the semaphore object s state is no longer signaled and no more threads can complete a wait on the semaphore object until some thread increases the count. Like usual semaphore objects, the RTSS semaphore objects are used for resource counting. They give a thread the ability to query the number of resources available; if one or more resources are available, the count of available resources is decreased. RTSS semaphores perform this test-and-set operation atomically; that is, when you request a resource from an RTSS semaphore, the operating system checks whether the resource is available and decrements the count of available resources without letting another thread interfere. Only after the resource count has been decreased does the system allow another thread to request a resource. Because several threads can affect an RTSS semaphore s resource count, an RTSS semaphore, unlike an RTSS mutex, cannot be owned by a thread. This means that waiting for semaphore objects: 44

55 Chapter 3: Using Using the RTX Functionality Will never return WAIT_ABANDONED ΠMay lose semaphore resources if threads are terminating However, unlike the usual semaphore objects, the RTSS semaphore objects support the waiting priority. That is, when there are several threads with the different priority waiting for an RTSS semaphore object, the system guarantees that the order of thread obtaining the semaphore object is the order of thread priority when the RTSS semaphore object is signaled. Inter-Process Communication via Semaphores To synchronize threads running in multiple processes, including RTSS processes and Win32 processes, a thread in each process must have its own process-relative handle to a single RTSS semaphore object. These handles can be obtained by calling either RtCreateSemaphore or RtOpenSemaphore. Using RtCreateSemaphore The first and most common way is for one thread in each process to call RtCreateSemaphore, passing the identical string for the parameter of RTSS semaphore name. The first thread to call RtCreateSemaphore will cause the system to create the RTSS semaphore object. As additional threads call RtCreateSemaphore, the system determines that an RTSS semaphore object with the specified name already exists; as a result, it does not create a new RTSS semaphore object but returns a process-relative handle identifying the existing RTSS semaphore object. A thread can determine whether RtCreateSemaphore actually created a new RTSS semaphore object by calling GetLastError immediately after the call to RtCreateSemaphore. If GetLastError reports ERROR_ALREADY_EXISTS, a new RTSS semaphore object was not created. Using RtOpenSemaphore Another method for obtaining the handle of an RTSS semaphore object involves a call to RtOpenSemaphore. The dwdesiredaccess parameter is ignored. The lpname parameter is the zero-terminated string name of the RTSS semaphore object. When the call to RtOpenSemaphore is made, the system scans all existing RTSS semaphore objects to see if any of them have the same name indicated by lpname. If the system finds an RTSS semaphore object with the specified name, it creates a process-relative handle identifying the RTSS semaphore object and returns the handle to the calling thread. Any thread in the calling process can now use this handle in any function that accepts an RTSS semaphore handle. If an RTSS semaphore object with the specified name cannot be found, null is returned. Environments The RTSS semaphore object is always maintained in the RTSS environment. However, Win32 programs may create, open, release, and wait for RTSS semaphores. This allows cooperation between RTSS and Win32 processes. The semaphore name space is separate from the Win32 semaphore name space. 45

56 Event Objects An event object is a synchronization object whose state can be explicitly set to signaled by using RtSetEvent or RtPulseEvent. The two types of event objects are: Manual-reset event An event object whose state remains signaled until it is explicitly reset to nonsignaled by RtResetEvent. While it is signaled, any number of waiting threads, or threads that subsequently specify the same event object in a call to RtWaitForSingleObject, can be released. Auto-reset event An event object whose state remains signaled until a single waiting thread is released, at which time the system automatically sets the state to nonsignaled. If no threads are waiting, the event object's state remains signaled. An event object is useful in sending a signal to a thread, indicating that a particular event has occurred. Using RtCreateEvent A thread uses the RtCreateEvent function to create an event object. The creating thread specifies the initial state of the object and whether it is a manual-reset or auto-reset event object. The creating thread can also specify a name for the event object. Threads in other processes can open a handle of an existing event object by specifying its name in a call to RtOpenEvent. For additional information about names for objects, see Object Names on page 43. Using RtPulseEvent A thread can use RtPulseEvent to set the state of an event object to signaled and then reset it to nonsignaled after releasing the appropriate number of waiting threads. For a manual-reset event object, all waiting threads are released. For an auto-reset event object, the function releases only a single waiting thread, even if multiple threads are waiting. If no threads are waiting, RtPulseEvent simply sets the state of the event object to nonsignaled and returns. Mutex Objects The RTSS mutex object is a synchronization object whose state is signaled when it is not owned by any thread and not signaled when the mutex is owned by a thread. The mutex object arbitrates exclusive access to a shared resource. Ownership A thread owns a mutex between the exit from a wait function and the call to RtReleaseMutex. No other thread can own the mutex between these calls. If another thread calls a wait function while the mutex is owned (not signaled), the wait function will not exit until the mutex owner releases the mutex. When an owning thread terminates, the mutex is signaled and abandoned. The waiter learns of an abandoned mutex by examining the wait function's return value. A thread that acquires an abandoned mutex should expect an inconsistent shared resource. If more than one thread is waiting for ownership, the thread with the highest priority gets ownership and is the first thread to return from the wait function. In cases where threads with 46

57 Chapter 3: Using Using the RTX Functionality the same priority are waiting to be owners, the earliest request goes first. Inter-Process Communication via Mutex Objects To synchronize threads running in multiple processes, including RTSS processes and Win32 processes, a thread in each process must have its own process-relative handle to a single RTSS mutex object. These handles can be obtained by calling either RtCreateMutex or RtOpenMutex. Using RtCreateMutex The first and most common way is for one thread in each process to call RtCreateMutex, passing the identical string for the parameter of RTSS mutex name. The first thread to call RtCreateMutex will cause the system to create the RTSS mutex object. As additional threads call RtCreateMutex, the system determines that an RTSS mutex with the specified name already exists; as a result, it does not create a new RTSS mutex object but returns a process-relative handle identifying the existing RTSS mutex object. A thread can determine whether RtCreateMutex actually created a new RTSS mutex object by calling GetLastError right after the call to RtCreateMutex. If GetLastError reports ERROR_ALREADY_EXISTS, a new RTSS mutex object was not created. If you are expecting to share this RTSS mutex with other processes, you can ignore this last step. Using RtOpenMutex Another method for obtaining the handle of an RTSS mutex involves a call to the RtOpenMutex. The dwdesiredaccess parameter is ignored. The lpname parameter is the zero-terminated string name of the RTSS mutex object. When the call to RtOpenMutex is made, the system scans all existing RTSS mutex objects to see if any of them have the same name indicated by lpname. If the system finds an RTSS mutex object with the specified name, it creates a process-relative handle identifying the RTSS mutex and returns the handle to the calling thread. Any thread in the calling process can now use this handle in any function that accepts an RTSS mutex handle. If an RTSS mutex with the specified name cannot be found, null is returned. Environments The RTSS mutex is always maintained in the RTSS environment. However, Win32 processes may create, open, and own RTSS mutex objects. The RTSS mutex name space is separate from the Win32 mutex name space. 47

58 Device Management Interrupts Real-time systems frequently are required to respond to external devices. In doing so, it is often desirable to have a real-time process respond directly to the interrupts generated by these devices. RTX allows a process to directly interface with a device without having to write a Windows driver. Interrupt Management The RTX interrupt management routines provide interfaces that enable an application to satisfy interrupt requests from devices attached to the computer. These interfaces let you attach a handling routine to an interrupt, much the same way that the RTX timer routines allow you to associate a handling routine with a given timer expiration. Win32 and RTSS processes can attach to an interrupt handler using RtAttachInterruptVector. The priority assigned to the interrupt handler thread determines the priority execution order of the interrupt handler in both the RTSS and Win32 environments. When an interrupt handler is attached to a particular interrupt, a thread is created which responds to the interrupt. This handling thread is analogous to an Interrupt Service Thread (IST). When the interrupt occurs, the interrupt source is masked; the interrupt s thread is resumed; and, if its priority is greater than the priority of the currently executing thread, it becomes the currently executing thread. After the interrupt handler returns, the interrupt source is unmasked and the thread is suspended. There are twelve interrupt levels availale to RTSS. The RtAttachInterruptVector call maps RTSS priorities into these twelve interrupt levels. These are, in increasing hardware priority: 0-117, 118, 119, For example, interrupts that require the highest hardware priority, the user should assign an RTSS priority of 127 when the interrupt is attached. For hardware interrupts of lesser priority, the user may choose from a range of For the lowest level priorities, use 117 or less. APIs The following APIs are available to manage RTX interrupt services: RtAttachInterruptVector attaches an IST to a specified interrupt. RtAttachInterruptVectorEx can attach an IST and/or an Interrupt Service Routine (ISR) to a specified interrupt. You can also share interrupts exclusively attached within either the RTSS or Win32 environments (but not both) with this call. RtReleaseInterruptVector releases an interrupt previously attached with RtAttachInterruptVector or RtAttachInterruptVectorEx. RtDisableInterrupts under the Win32 environment disables interrupt handling for all interrupts attached to a process. In the RTSS environment, all interrupts are disabled at the 48

59 Chapter 3: Using Using the RTX Functionality processor level. RtEnableInterrupts enables all interrupts disabled by RtDisableInterrupts. General Programming Considerations As with any thread, an interrupt thread can be preempted at any time by a thread that runs at a higher thread priority level. Time slicing effects the execution of ISTs if there is a time quantum set for the IST. ΠInterrupt processing can be disabled for the set of interrupts attached to the RTX process by raising the thread priority level of the currently executing thread. The level must be higher than all of the thread priority levels specified for the RTSS Interrupt Service Threads. An interrupt handler that signals an object may satisfy the wait conditions of a higher priority thread. Resuming the higher priority thread will delay the completion of the interrupt handler and delay the time at which the interrupt source will be unmasked. High priority threads never mask timer interrupts; thus, the timer interrupt is effectively the highest priority interrupt. To mask timer interrupts, use RtDisableInterrupts. Win32 Environment Programming Considerations All processing in the RTSS environment takes priority over all processing in the Win32 environment. Therefore, any time-critical interrupt processing that must be accomplished should be done with a handler running an RTSS process, rather than a Win32 process. In the Win32 environment, the Windows NT and Windows 2000 schedulers service RTX interrupt threads. This can lead to non-deterministic scheduling latencies for the handling thread to receive and process the interrupt. Using RtAttachInterruptVector To attach an interrupt vector, use RtAttachInterruptVector. To use this call, you must supply bus-specific parameters. For buses with automatic configurations, such as PCI you can obtain the parameter information by calling RtGetBusDataByOffset. For more information, look in the Bus I/O section of this manual. Using RtAttachInterruptVectorEx Use RtAttachInterruptVectorEx to share interrupt vectors. This function lets you associate a handling routine with a hardware interrupt on one of the supported buses on the computer. RTSS threads can share a given interrupt vector, and Win32 threads can do the same. However, an RTSS thread and a Win32 thread cannot share the same interrupt. To determine what interrupts Windows NT is using, use Windows NT Diagnostics. To determine what interrupts Windows 2000 is using, look in Device Manager. You should be aware that sharing of interrupts increases the interrupt latency for the lower priority interrupt service threads; this occurs because the higher priority interrupt service thread must run and determine that a shared interrupt is to be passed along to another thread. For situation where very low interrupt latency is necessary, the extra overhead of interrupt sharing could cause problems. Devices that require very short interrupt latency should be assigned to unique interrupt lines. If your device has hard real-time interrupt latency requirements, you probably do not want it to share an interrupt line with another device. 49

60 Level-triggered interrupts cannot be used by Win32 processes because the interrupt will be reasserted when RTSS tries to return to Windows NT to allow the Win32 service routine to run. For level-triggered interrupts to operate correctly, the interrupt service routine must clear the interrupt condition before it unmasks the interrupt line. This limitation is found on uniprocessor systems only. Using RtReleaseInterruptVector Unlike driver unloading, an RTX application can exit and leave a device enabled, with the device attempting to deliver interrupts to the handling thread. Although the RTX library usually cleans up after an application exits, there are times when the exiting application can bypass the library s attempt to detect the exit. To avoid such a condition, use RtReleaseInterruptVector; it will release a previously attached interrupt. Note: Just as in an interrupt service routine in a device driver, a real-time application must be able to acknowledge an interrupt and control the device that generated it. For further details on communicating with devices, see the Port I/O and Physical Memory Mapping sections that follow. Programming Example (Interrupt Management and Port I/O Calls) Port IO See the Interrupt Management and Port I/O Calls Programming Example in Code and File Examples. It demonstrates the use of RTX interrupt management and port I/O calls. Real-time systems require the ability to control, read, and write data to hardware devices. The RTX port I/O programming interfaces allow data movement in the I/O space of a processor by a user process without the need to switch to a kernel-mode code. This functionality eliminates the need for creating a device driver for every device that must be accessed. Additionally, it eliminates the latencies associated with requesting device driver services for every device access. Port I/O provides an alternate method of communicating directly with hardware. The I/O address space is a feature found on Intel processors where each address represents an 8-bit "port." Each port typically corresponds to an 8-bit control register on a hardware device. While sequential addresses can represent the bytes in a multi-byte port, hardware designers usually employ designs that have a single-byte port, and multi-byte values are entered as sequential single-byte writes to the port address. For details about a particular device, you should consult its programming reference documentation. Access to port I/O devices must be enabled prior to attempting any data transfers. This is accomplished with the RtEnablePortIo function by passing in the port I/O address range that will be accessed. Subsequent to enabling access, the RtWrite* and RtRead* functions, discussed below, may be used to transfer data to and from the enabled port I/O space. Port I/O Control APIs The following APIs are available to access Port I/O control services: RtEnablePortIo enables the direct Port I/O access for the specified range of I/O 50

61 Chapter 3: Using Using the RTX Functionality addresses. RtDisablePortIo disables the direct Port I/O access for the specified range of I/O addresses. Port I/O Data Transfer APIs (described in the section that follows) Port I/O Data Transfer APIs The following APIs are available to access Port I/O data transfer services: RtReadPortUchar,RtReadPortUshort,RtReadPortUlong directly reads a one-, two-, or four-byte datum from the specified I/O port. RtWritePortUchar,RtWritePortUshort,RtWritePortUlong directly writes a one-, two-, or four-byte datum to the specified I/O port. RtReadPortBufferUchar,RtReadPortBufferUshort,RtReadPortBufferUlong copies a series of one-, two-, or four-byte datum from the specified I/O port to a buffer. RtWritePortBufferUchar,RtWritePortBufferUshort,RtWritePortBufferUlong copies a one-, two-, or four-byte datum from the specified I/O port to a buffer. General Programming Considerations The RTX interfaces are coded in assembly and use the stdcall convention, indicating that the subroutines handle the stack cleanup. You should not use other calling conventions. Programming Example See Interrupt Managemet and Port I/O Calls Programming Example in Code and File Examples in Appendix A. It demonstrates the use of RTX interrupt management and port I/O calls. Physical Memory Mapping The existence of an I/O space is dependent on the processor architecture. Several Windows NT and Windows 2000-supported architectures are based on processors that do not have a separate I/O space. Rather, their ports are mapped into memory addresses. These architectures can use the memory mapping function to enable access to physical memory on controllers and other hardware devices. Physical memory mapping can also be used to give processes access to physical memory ranges in the CPU s address space. The RTX physical memory map interface maps a section of physical memory into an application s virtual address space. This enables the application to access a region of physical memory directly, as if it were a buffer in the application. This interface is useful for applications that need to access device memory or registers that are mapped into the physical address space of the CPU. APIs The following APIs are available to access RTX memory mapping services: 51

62 RtMapMemory maps a physical memory address range into the process virtual address space. RtUnmapMemory removes a previously mapped physical memory object from the process virtual address space. General Programming Considerations There are no restrictions or protections on the mapped memory region. The mapping will provide precisely the base address and length specified, if successful. You should take care not to map in and modify Windows NT or Windows 2000 address space as this may lead to corruption of either operating system. Win32 Environment Programming Considerations Accesses beyond the address range allocated in the mapping will result in an exception. Programming Example (RTX Memory Mapping Calls) See the RTX Memory Mapping Calls Programming Example in Code and File Examples in Appendix A. Contiguous Memory Mapping Certain devices, particularly devices that perform DMA, require that their buffers reside in physically contiguous memory in the CPU s address space. In addition, these devices must access the memory buffers using the actual physical address, rather than by the virtual address that is used by a Win32 or an RTSS process. The RtAllocateContiguousMemory and RtGetPhysicalAddress functions are used to allocate physically contiguous memory and to translate the virtual address of the memory to a physical address, respectively. APIs The following APIs are available to access RTX contiguous memory allocation services: RtAllocateContiguousMemory allocates a physically contiguous memory address range and maps that memory into the process virtual address space. RtFreeContiguousMemory frees a previously allocated physically contiguous memory region. RtGetPhysicalAddress returns the physical address for the virtual address of a previously allocated physically contiguous memory region. Programming Considerations Contiguous memory is always allocated from the non-paged pool of memory maintained by Windows NT and Windows This pool of memory is relatively small and is rapidly fragmented by the allocations of other drivers and subsystems in Windows NT and Windows 2000 shortly after system boot. To avoid failure of large allocations, you should minimize their use and/or ensure that they are accomplished shortly after system boot. 52

63 Chapter 3: Using Using the RTX Functionality In the Win32 environment, RtGetPhysicalAddress operates only with addresses returned by RtAllocateContiguousMemory. Programming Example (RTX Contiguous Memory Allocation Calls) Bus IO See the RTX Contiguous Memory Allocation Calls Programming Example in Code and File Examples in Appendix A. It demonstrates the use of RTX contiguous memory allocation calls. RtGetBusDataByOffset, RtTranslateBusAddress, and RtSetBusDataByOffset facilitate the development of RTSS hardware drivers. Each function eases the gathering of specific hardware information and/or setting hardware. RtGetBusDataByOffset is used primarily in support of attaching a driver to a hardware device by obtaining device information required for input to RtAttachInterruptVector, such as the bus number, interrupt level, and interrupt vector. For example, by issuing a call to RtGetBusDataByOffset, a PCI bus can be scanned, detect a particular device, and then return the bus number where the device resides, the bus interrupt level, and interrupt vector. For further information, see RtAttachInterruptVector and RtAttachInterruptVectorEx in the RTX 5.0 Reference Guide. Setting hardware is accomplished with a call to RtSetBusDataByOffset. This function is useful when device initialization requires clearing or setting of status registers, slot, and so on. RtTranslateBusAddress is used to translate a device-specific memory address range into the logical address space of a driver. Programming Example (Bus I/O) File IO See the Bus I/O Programming Example in Code and File Examples in Appendix A. The code fragment illustrates each of the Bus I/O calls in a PCI driver. File IO RTX allows two options for file input and output (I/O). You can write to the supported file I/O functions in the Win32 API or to the supported file I/O functions in the C run-time library. The API delivers low-overhead, fast access to Windows NT and Windows 2000 file I/O capabilities using standard APIs. A subset of CreateFile flags are supported with file I/O. Please refer to the RTX 5.0 Reference Guide for more details. File I/O does not include support for asynchronous file operations. Because RTSS applications have no current-directory notion, RTSS file I/O requests must use fully qualified path names, such as: c:\temp\myfile.txt (for a file system object) 53

64 \\.\MyDevice0 (for a device object) RTSS file I/O calls are made from the Windows NT or the Windows 2000 kernel environment: RTX actually translates Win32 names such as c:\myfile.txt and \\.\MyDevice0 to NT internal names \??\c:\myfile.txt and \Device\MyDevice0, respectively. You can, therefore, use Windows NT and Windows 2000 internal names from your RTSS applications, although such calls fail in Win32. Using an internal Windows NT or Windows 2000 name lets you access a device object for which Win32 has no symbolic link, such as \Device\beep or \Device\Harddisk0\Partition1\testfile.txt. With boot-time file I/O, you may only use paths such as \\Device\\Harddisk0\\Partition1\foo.txt because paths such as \\??\\C:\\foo.txt and C:\\foo.txt are not supported. 54

65 Chapter 4 Developing an Application This chapter discusses the two types of real-time dynamic link libraries (RTSS DLL and RTDLL), and provides references to code examples for each type. It also explains how to use the C run-time library functions and floating point; provides guidance on writing device drivers; explains exception handling in the RTSS and Win32 environments; and provides techniques for managing starvation conditions. This chapter contains information on: Using the RTX Makefile Using RTX Dynamic Link Libraries Using the C Run-time Library Functions Using Floating Point Writing RTSS Device Drivers C++ and Structured Exception Handling System Exception Handling About System Exception Handling RTX Handler Tables of Exceptions RTX Exception Handling About RTX and Windows NT / WIndows 2000 Stop Messages Interpreting Windows NT Blue Screen Stop Messages Interpreting RTX Green Screen Stop Messages Starvation Management Power Management 55

66 Using the RTX Makefile Variables You can use the RTX master makefile (rtx.mak) to build both RTSS and Win32 versions of a particular program. Rtx.mak contains rules to compile C files and link the resulting objects. You can specify Win32 executable (.exe) files in a makefile using rtx.mak because rtx.mak includes win32.mak. The master makefile uses the following variables: NODEBUG Calls the link using the /RELEASE option. RTSS_CRT Includes the RTSS C run-time library for single-threaded applications in the final link of the RTSS executable. RTSS_MTCRT Includes the RTSS C run-time library for multi-threaded applications in the final link of the RTSS executable. USER_LIBS Additional user-specified libraries that will be included in the link stage. RTSS_OBJS, RTDLL_OBJS List of object files linked by rtss link or rtdll link makefile rules, respectively. Sample Makefile See the Makefile Sample in Code and File Examples in Appendix A. 56

67 Chapter 4: Developing an Application Using RTX Dynamic Link Libraries This topic provides: n n Descriptions of the two types of real-time DLLs (RTSS DLL and RTDLL) C Run-Time Libraries: Programming Considerations for DLLs n References to RTSS DLL and RTDLL code examples For instructions on creating DLLs, see Creating RTX Dynamic Link Libraries on page 25. About RTSS DLLs and RTDLLs There are two types of real-time DLLs (RTSS DLL and RTDLL) that you can use to share code between processes or make run-time determinations of what libraries need to be loaded for a given hardware configuration. RTSS DLLs An RTSS DLL is actually not a DLL but an RTSS process that exports functions for use by other RTSS processes. It shares a common address space with RTSS processes. They can be loaded either at boot time or through a call to Windows NT from within a C/C++ program (e.g., System("RTSSrun LibName.rtss"). Although similar to RTSS applications, their entry point is Main, and they are compiled and linked to generate a library of exported functions that can be linked with RTSS applications. Typically, Main for an RTSS DLL will simply issue a SuspendThread call. RTSS DLLs allow you to reference exported functions by name in a calling program, but are cumbersome to load because they are neither loaded nor unloaded automatically when RTSS applications using them start running. RTDLLs RTDLLs are RTSS objects that can be dynamically loaded and unloaded using the LoadLibrary and FreeLibrary calls. They are automatically unloaded from memory when the last RTSS process referencing them terminates. Because RTDLLs do not require linking to an explicit export library, they provide a convenient, flexible runtime accommodation of changes to RTDLLs or applications. However, with RTDLLs the address of each exported function used by a calling process must be explicitly obtained through a call to GetProcAddress. Additionally, because RTDLLs are not RTX processes, it is not reliable to use C run-time functions within an RTDLL loaded by more than one RTX process simultaneously. For further details about the relationship between C run-time libraries and RTDLLs see C Run-Time Libraries:Programming Considerations for DLLs below. The choice of RTSS DLLs or RTDLLs for a particular application depends on the specific functional requirements of the application. The variation of hardware run-time configurations that an application must accommodate may also affect your choice. Programming examples for RTSS DLLs and RTDLLs are provided in the sections that follow. C Run-Time Libraries: Programming Considerations for DLLs This section discusses considerations that you should keep in mind when designing an RTSS DLL or RTDLL that will be linked with the RTX-supplied C run-time libraries, RTXlibc.lib or RTXlibcmt.lib (see Using the C Run-time Library Functions on page 59). The Microsoft C run-time initialization code assumes that global variables have process 57

68 scope, i.e., a separate copy of all C run-time global variables and structures exists for each process using the libraries. This is not true for RTSS DLLs or RTDLLs. RTSS DLLs Because RTSS DLLs are RTSS processes which have been linked to generate an export library, and because they never get unloaded from memory except at shutdown, global structures created at initialization will persist during the entire life of any process depending on the RTSS DLL. Note: A few C run-time routines are unsafe within an RTSS DLL used by multiple processes. The routines that you should not use are: fprintf(), getenv(), perror(), printf(), vsprintf(), and wprintf(). Because these routines rely on per-process global variables, they can yield undefined behavior that may require system reboot. Note that in this context "used by multiple processes" means used by more than one process at any time between system startup and shutdown, including the same RTSS image, running twice in succession with the same RTSS PID. RTDLLs RTDLLs are not RTSS processes; they are RTSS objects which can be dynamically loaded and unloaded. Because other objects created by an RTDLL are always owned by the calling process, they are destroyed when that process terminates. Among other things, the C run-time initialization creates heaps used for memory allocation. These heaps persist only until the process that initially loaded the RTDLL terminates. Since the behavior of C run-time functions is reliable only in an RTDLL loaded by multiple processes given strict limitations on the LoadLibrary, FreeLibrary sequence, it is recommended that you never register RTDLLs linked with the C run-time libraries with the /s switch of RTSSrun. RTSS DLL and RTDLL Code Examples See RTSS DLL Code Example and RTDLL Code Example in Code and File Examples in Appendix A. 58

69 Chapter 4: Developing an Application Using the C Run-time Library Functions Using Floating Point RTX provides support for C run-time library functions. The RTX-supplied C run-time libraries are based on the Microsoft Visual C++, C run-time libraries. The RTX libraries, named RTXlibc.lib and RTXlibcmt.lib (indicating single and multi-threaded libraries), provide improvements to the efficiency of memory allocation (malloc). Other than this improvement, they do not differ substantially from the Microsoft libraries. For a list of available functions, see the C Run-Time API List in the RTX 5.0 Reference Guide. Threads that run in the RTSS environment always run in kernel mode. Whereas the Windows NT and Windows 2000 kernel does not support floating-point operations in kernel-mode code (such code causes the system to crash), RTX allows RTSS threads to use the Floating-Point Unit (FPU) to perform floating-point operations. Enabling Floating-Point Support in RTSS Programs If you build RTSS programs using NMAKE, you must add the following line to your makefile before the line that includes rtx.mak: RTSS_CRT = 1 The preceding line enables Floating-Point Unit (FPU) support, including the floating-point math routines and printf with floating-point support. If you are using Microsoft Visual Studio, follow the procedure to enable C run-time support as described in Using Microsoft Visual Studio 6.0. Running RTSS Programs Using Floating-Point You do not need to follow any special procedures to run an RTSS program that uses floatingpoint. The program can simply issue Floating-Point Unit (FPU) instructions and call floatingpoint math routines as done by a standard Win32 program. Writing RTSS Device Drivers RTX provides a number of features that enable you to quickly and easily develop device drivers. The RTX device driver model is simpler than that of Windows NT and gives you greater flexibility in design. Because Windows NT and Windows 2000 device drivers are often user-mode drivers and rely on user-mode Windows NT and Windows 2000 services, they cannot be used "as-is" with RTSS applications. Furthermore, since even kernel-mode drivers are often accessed through user-mode libraries supplied by hardware vendors, it is generally not possible to access standard Windows NT and Windows 2000 device drivers from within an RTSS application. Devices can be accessed and controlled through three types of functions: Port I/O, Bus I/O, and mapped memory. Additionally, drivers can respond to devices by providing interrupt handlers through RtAttachInterruptVector. Unlike Windows NT, where access to drivers 59

70 occurs via calls to DeviceIoControl, RTSS drivers can be structured as static libraries, RTSS DLLs, or RTDLLs. In each case, the driver writer can supply library functions directly to the RTSS application writer without the need to employ the DeviceIoControl interface. For many applications, it is not necessary to write a hard real-time (RTSS) device driver for standard desktop devices. When hard real-time performance is not required for device access, as is often the case with video, sound, and network devices, the recommended approach is to develop a Win32 application that communicates with RTSS applications through IPC mechanisms, and communicates with necessary devices through standard Windows NT device drivers. C++ and Structured Exception Handling RTX supports Microsoft C++ exceptions (catch/throw), Win32 Structured Exception Handling (SEH) API, and C frame-based exception handling (try/except/finally), all as defined by the Win32 Platform SDK. This topic discusses: C++_Support ΠStructured_Exception_Handling C++ Support RTX supports the Visual C++ language, with some restrictions discussed in the note below. RTSS should support any C++ features usable in a Win32 C++ RTX API console application, including new/delete operators and exception handling. Note: RTX does not claim support for all C++ libraries. Support is limited to libraries that depend upon the set of Win32 functions supported in the RTSS environment. You can test specific libraries to determine whether they are supported by RTX. Structured Exception Handling RTSS supports Structured Exception Handling and C++ exceptions, as described by the Win32 Platform SDK, including: Win32 Structured Exception Handling calls, which include RaiseException, SetUnhandledExceptionHandler, UnhandledExceptionFilter, AbnormalTermination, GetExceptionCode, GetExceptionInformation Frame-based exception handlers: try-except and try-finally. C++ exception handling: try-catch. ΠHandling for the following software exceptions in RTSS: EXCEPTION_DATATYPE_MISALIGNMENT EXCEPTION_BREAKPOINT EXCEPTION_ACCESS_VIOLATION EXCEPTION_ILLEGAL_INSTRUCTION EXCEPTION_FLT_DENORMAL_OPERAND 60

71 Chapter 4: Developing an Application Using SEH EXCEPTION_FLT_DIVIDE_BY_ZERO EXCEPTION_FLT_INEXACT_RESULT EXCEPTION_FLT_INVALID_OPERATION EXCEPTION_FLT_OVERFLOW EXCEPTION_FLT_UNDERFLOW EXCEPTION_INT_DIVIDE_BY_ZERO To use SEH in an RTSS application, an application must be linked with a Win32 staticlinkage run-time support library (such as RTXlibc.lib or RTXlibcmt.lib which contain runtime support for the SEH frame-based exception handlers), or with static-linkage run-time support C++ libraries. Differences Between Win32 and RTSS Exception Handling The RTSS implementation follows Win32 SEH semantics where possible. This section describes the differences. UnhandledExceptionFilter Win32 UnhandledExceptionFilter semantics provide the option to disable the exceptionrelated dialog box pop-up via SetErrorMode with the SEM_NOGPFAULTERRORBOX flag. On an exception, RTSS always displays a pop-up saying that the application has been frozen or unloaded. Exception caused by a thread When a thread of a multithreaded application causes an exception in Win32, the system displays a dialog box. Until the user responds to the box, other threads of the application continue running. Once the user has responded, all threads of the application terminate. RTSS acts differently; it freezes (or unloads, if so configured) all threads of a process whenever any of them gets an exception, and produces an informational pop-up. This behavior is safer and more intuitive in the RTSS context. You can, however, emulate the Win32 behavior by using per-thread unhandled exception filter functions. Nested exceptions and collided unwinds RTSS follows Win32 rules for nested exceptions and "collided" unwinds, with a few minor differences: Non-continuable exceptions Non-continuable exceptions caused by the program directly or by exception handling run-time itself. Win32 repeatedly re-asserts those; but repeated re-assertion of exceptions consumes stack space. A stack fault in RTSS causes a system shutdown (the "green screen"), so for robustness, RTSS terminates a process that has generated a non-continuable exception. Hardware exceptions RTSS exception codes for hardware exceptions are tied to Pentium interrupt codes, thus differing from Win32 exception codes caused by similar errors. For example, an errant Win32 application gets an EXCEPTION_ACCESS_VIOLATION 61

72 Debugging as defined by Win32, an RTSS application gets EXCEPTION_PAGE_FAULT as described in the RTX Reference Guide. A Win32 EXCEPTION_ILLEGAL_INSTRUCTION is equivalent to the RTSS EXCEPTION_INVALID_OPCODE. Reads/writes of address 0 Win32 explicitly guarantees that the first 64K of a user process's address space is unmapped, so any access of that area causes an exception. However, Windows NT and Windows 2000 occasionally make this area valid for kernel processes and device drivers (and, therefore, for RTSS). This means that a write to/read from address 0 from an RTSS process may occasionally succeed, rather than cause an exception. For debugging, see the Debug tab in the RTX Properties control panel. General User Notes for Exception Handling Exception handling is a powerful mechanism with often subtle semantics. It is quite easy to write code that causes infinite re-assertion of an exception. For example, if a filter expression always faults, or always dismisses a hardware exception which gets re-executed, the process continues generating exceptions until it overflows the stack. Miscasting the handler argument to SetUnhandledException filter may be equally fatal. Because stack faults in RTSS cause system shutdown, you must be careful when writing exception handlers. Testing your application in Win32 becomes more important than ever to avoid stack overflows in RTSS. System Exception Handling About System Exception Handling An exception is a forced transition from normal program execution to a specialized procedure, called a handler, which processes the exception. An exception is raised (occurs) when the CPU encounters an error condition during program execution. Each exception is assigned an error code or vector number. For example, if the CPU encounters a divide by 0, exception 0 is raised. For a complete discussion of exception handling, see Volume 3: Architecture and Programming of the Pentium Processor Family Developer's Manual. Important: All discussions in this chapter ("System Exception Handling") assume that RTSS applications do not use Structured Exception Handling (SEH). For information on SEH, see C++ and Structured Exception Handling. RTX Handler RTX provides a handler to process exceptions that occur in an RTSS process. (If an exception occurs in a native Windows NT or Windows 2000 application, the Windows operating system handles it.) When the RTX handler encounters an error, it initiates one of the following actions: Freezes and/or terminates the process 62

73 Chapter 4: Developing an Application Modifies the application environment and continues ΠExecutes an orderly shutdown, known as a "Green Screen" Note: If an exception occurs within an ISR (such as an RTX harware interrupt or RTX timer interrupt), RTX immediately initiates an RTX Green Screen stop message. If a fault occurs during exception processing, the RTX handler immediately initiates a double fault and Green Screen stop message. Tables of Exceptions This topic contains tables of the following types of exceptions: RTX exceptions ΠIntel exceptions RTX Exception Codes The table that follows lists the exception name, the vector number or error code, and the exception handler response. ([FHSWLRQ (UURU&RGH 57;ZLOO (;&(37,21B13;B127B$9$,/$%/( ; $OORZIRUIORDWLQJSRLQW FDSDELOLW\DQGFRQWLQXH H[HFXWLQJWKHDSSOLFDWLRQ (;&(37,21B,17 [ (QWHUWKHGHEXJJHU,IQR GHEXJJHULVSUHVHQW57;IUHH]HV WKHSURFHVV (;&(37,21B10, (;&(37,21B'28%/(B)$8/7 (;&(37,21B5(6(59('B75$3 (;&(37,21B,19$/,'B766 Intel Exception Codes [ [ [) [$,VVXHD*UHHQ6FUHHQVWRS PHVVDJH Following Win32 behavior, RTSS maps the Intel (x86) exception code to the Win32 one, and then invokes Structured Exception Handling. RTX will alert the user via a popup message, make an entry to the event log, and freeze or terminate the thread and associated process. [([FHSWLRQ (;&(37,21B',9,'('B%<B=(52 (;&(37,21B13;B29(5581 (;&(37,21B13;B(5525 (;&(37,21B,19$/,'B23&2'( (;&(37,21B*3B)$8/7 (;&(37,21B3$*(B)$8/7 :LQ0DSSLQJ (;&(37,21B,17B',9,'(B%<B=(52 (;&(37,21B)/7B',9,'(B%<B=(52 (;&(37,21B)/7B,19$/,'B23(5$7,21 (;&(37,21B)/7B'(1250$/B23(5$1' (;&(37,21B)/7B',9,'(B%<B=(52 (;&(37,21B)/7B29(5)/2: (;&(37,21B)/7B81'(5)/2: (;&(37,21B)/7B,1(;$&7B5(68/7 (;&(37,21B)/7B,19$/,'B23(5$7,21 (;&(37,21B,(*$/B,16758&7,21 (;&(37,21B$&&(66B9,2/$7,21 63

74 [([FHSWLRQ (;&(37,21B%281'B&+(&. (;&(37,21B6(*0(17B127B35(6(17 (;&(37,21B'(%8* (;&(37,21B$/,*10(17B&+(&. :LQ0DSSLQJ (;&(37,21B%5($.32,17 (;&(37,21B'$7$7<3(B0,6$/,*10(17 RTX Exception Handling For most exceptions, the RTX handler performs the following tasks: Freezes or terminates the errant RTSS process, depending on the state of the ExceptionDisposition flag Alerts the user with a popup window ΠWrites one or more associated entries in the event log The sections that follow describe each of these tasks. Freeze or Terminate Processing The ExceptionDisposition registry flag, settable from the RTX Properties Control Panel, controls the disposition of faulting RTSS processes. Possible values are: Alert User 0 = Terminates processing (default) 1 = Freezes the thread and processing The RTX handler alerts the user of an exception with a popup message window. For example, if the handler terminates processing, RTX might display the following window: RTX Exception - Memory Access Fault at loc FEBEB229 (Proc= , Thread=804526F8) Process image has been * unloaded * In this example, a memory protection fault has been detected. The message identifies the application instruction address and the process and thread identification values. The disposition of the thread is unloaded. If the RTX handler freezes processing, RTX might display the following window: RTX Exception - Memory Access Fault at loc FEBDF229 (Proc= , Thread=804526F8) Process image has been * frozen * Debug and/or use "RTSSkill" command to unload all processes In this example, a memory protection fault has been detected. The message identifies the application instruction address and the process and thread identification values. The disposition of the thread is frozen. The user is directed to manually terminate the process using RTSSkill. 64

75 Chapter 4: Developing an Application Generate Event Log Entries The event log message includes an information entry, which is the text portion of the popup window, and an error entry that provides details about the error. The error entry contains two parts: a description and binary detail. The binary detail consists of 10 dwords of message data and 3 dwords of RTSS fault data, as illustrated in the sample that follows. The description for Event ID (12) in Source (Rtx_rtss) could not be found. It contains the following insertion string(s): \Device\Rtx_rtss, RTX Exception - Memory Access Fault 0000: c004000c 0010: c : feac12e8 febdf : f8 The first 10 entres in the message dump are` specific to the error logging call and are ignored. The 3 dwords of RTSS fault data are: Instruction pointer value (febdf229 in the sample) RTSS process identification ( in the sample) ΠRTSS thread identification (804526f8 in the sample) Caution: To preserve event log information, do not filter event entries. About RTX and Windows NT / Windows 2000 Stop Messages Stop messages, presented via an RTX Green Screen or a Windows NT Blue Screen, quickly provide you with key information about a system crash. A stop message often gives you sufficient data to determine why a system has crashed and what actions to take to resolve the problem. To enable (view) stop messages, you must disable the Windows NT Automatically Reboot option as shown in the procedure that follows. To enable stop messages 1. In the Windows NT Control Panel, double click the System icon and then open the Startup/Shutdown tab. 2. In the Recovery section, deselect the Automatically Reboot option. Note: You should select the Automatically Reboot option only if you want to disable stop messages and have the system reboot automatically when there is a system failure. Click OK to save the settings. 65

76 Interpreting Windows NT Blue Screen Stop Messages When a non-recoverable exception occurs within a native Windows NT application, Windows NT initiates a Blue Screen. The Windows NT Blue Screen contains four sections of data, with the most important information contained in the first two lines. These two lines contain the stop error code, its four parameters, and the text of the stop error message. You should always record the first few lines, along with the driver list (in the second Blue Screen section), before rebooting the computer. With this data, you can often diagnose the source of a stop condition. Note: Under some conditions, the kernel displays only the top line of the stop message because the services required to display the rest of the information may not be available. Section 1 - Stop Message The Stop Message section provides the bugcheck data in the form: ***STOP: #E(#1, #2, #3, #4) Text interpretation of the error where #E = Actual error code. #1 - #4 = Additional parameters relating to the error. Text = Best effort interpretation of the error. Section 2 - Driver List The Driver List is a two-column display that lists all drivers loaded on the computer at the time the stop message occurred, along with their base addresses in memory and date stamps of the driver file dates. This section is important because many stop messages contain the address of the instruction that caused the error. If the address falls within the base address of one of the drivers on this list, then that driver may be the cause of the crash. Section 3 - System Stack Dump The System Stack Dump lists some of the calls on the stack that preceded the stop message. Sometimes, the first few lines indicate what component or driver caused the error. You should note, however, that the last calls on the stack are not always the cause of the problem. The stack dump also provides the names of modules along with their starting addresses. To get a more detailed stack trace, use a kernel debugger such as WinDbg. 66

77 Chapter 4: Developing an Application Section 4 - Communication The Communication section of the Blue Screen provides confirmation of the communication parameters used by a kernel debugger (if present on the target computer). The following message then appears: Restart and set the recovery options in the system control panel or the /CRASHDEBUG system start option. If the error persists enable the Kernel Debugger in either DEBUG or CRASHDEBUG mode on your computer. Consult the Windows NT Debugger documentation for instructions on configuring the computer for debugging This message implies that if the computer is restarted, the stop condition may not happen again. If this message reappears after you restart, contact your system administrator or technical support group. To obtain additional information about a system stop 1. In the Windows NT Control Panel, double-click the System icon and then open the Startup/Shutdown tab. 2. In the Recovery section, select the Write Debugging Information option and then click OK to apply the change. Note: When this option is selected, the system memory dump will be written to %SystemRoot%\memory.dmp after a crash. 3. Copy the system symbol files (*.dbg) from the Windows NT installation CD and the RTX-supplied *.dbg files to %SystemRoot%\symbols. 4. Install the dumpexam.exe utility (also on the installation CD). 5. Reboot your system and then run the dumpexam utility. For more detailed system information concerning the crash, consult the dumpexam text output. 67

78 Interpreting Windows 2000 Stop Screens For Windows 2000 the traditional "Blue Screen" has been eliminated. The user can still obtain the same type of information by using the "minidump" or small memory dump option. All that is needed is a small 2mb paging file on the system drive and configuring the Startup and Recovery Options for minidump on the System properties screen. This dump file type includes the following information: The stop message and parameters, as well as other data A list of loaded drivers ΠThe processor context (PRCB) for the processor that stopped ΠThe process information and kernel context (EPROCESS) for the process that stopped ΠThe process information and kernel context (ETHREAD) for the thread that stopped ΠThe Kernel-mode call stack for the thread that stopped This kind of dump file can be useful when space is limited. However, because of the limited amount of information included, errors that were not directly caused by the thread running at the time of the problem may not be discovered by an analysis of this file. The Windows 2000 support tool dumpchk.exe will be required to generated text from the binary dump. Refer to the following Microsoft documentation: Reading Small Memory Dump Files Created by Windows 2000 Windows 2000 Memory Dump Options Overview 68

79 Chapter 4: Developing an Application Interpreting RTX Green Screen Stop Messages When a non-recoverable exception occurs within an RTSS process, the RTX exception handler initiates a Green Screen. The RTX Green Screen contains four sections of data. Sections 1 and 2 are RTX specific. Sections 3 and 4 are similar to those sections of the Windows NT Blue Screen. Section 1 - RTSS-Specific Stop Message This Stop Message section provides the bugcheck data in the form: *** RTX/RTSS Stop : #E(#1, #2, #3, #4) Text interpretation of the error where #E = Actual error code. Error code numbers and their associated text are: 1. UNHANDLED_EXCEPTION 2. THREAD_STACK_OVERFLOW 3. LOCK_HIERARCHY_VIOLATION 4. LOCK_OWNER_VIOLATION 5. PROXY_DISPATCHER_SANITY 6. PROXY_THREAD_SANITY 7. SERVER1_SANITY 8. EXCEPTION_IN_ISR 9. KERNEL_MODE_EXCEPTION 10. SYSTEM_PROCESS_EXCEPTION 11. NMI_EXCEPTION 12. STACK_OVERFLOW #1 = Exception code taken from Exception Table. #2 = Contents of Instruction Pointer Register at the time exception was raised. If the #2 value is outside the address range of the process, the most likely cause of the exception is a corrupt stack with an illegal value restored to the IP. #3 = RTSS Thread identification. #4 = RTSS Process identification. 69

80 Section 2 - HAL-Supplied Stop Message This Stop Message section provides the bugcheck data in the form: *** STOP: #E(#1, #2, #3, #4) *** Address XXXXXXXX has base at YYYYYYYY-Kernel Image where #E = 0 (zero). Indicates that an RTSS process caused the exception. Other codes are reserved for internal RTX errors. #1 = Hardware exception vector number. #2 = Contents of Instruction Pointer Register at time exception was raised. #3 = Stack pointer at time of fault. #4 = Base address of the exception frame. For the majority of exceptions, an exception stack frame containing the system state information is stored on the current stack. In the case of a double fault, this address will be the base address of the Task State Segment. For more information, see Volume 3: Architecture and Programming of the Pentium Processor Family Developer's Manual. Text = The text interpretation attempts to match one of the entries in the stop message to a loaded image base address to determine approximately where the fault was raised. Starvation Management This topic discusses the RTX watchdog timer and programming techniques that you can use to manage starvation conditions. Watchdog Timer When a single RTSS thread becomes CPU bound, it is often the result of a program logic error (which occurs most frequently during the development phase). When a thread becomes CPU bound on a single-processor system, Windows NT and Windows 2000 both freeze. On a multi-processor system, the both Windows operating systems continue to run but cannot terminate the CPU-bound thread because the lower priority Service Request Interrupt (SRI) manager threads will not run. Watchdog Management For this type of condition, you can use the RTX starvation management watchdog timer. This timer checks on every timer interrupt (which is normally always enabled) for continuous running of the same thread and/or RTSS threads to the exclusion of Windows NT (the idle thread). When the watchdog timer expires, an exception is raised; a popup message notifies you of the error; and then Windows NT and Windows 2000 resume normal operation. The offending process is either stopped or terminated, based on the Process Exception Disposition setting in the RTX Settings control panel. You can use the RTSSkill utility to unload the stopped process. 70

81 Chapter 4: Developing an Application Setting the Starvation Time Out Period You can set the Starvation Time Out period using from the Settings tab of the RTX Properties control panel. Values are: 0 = Disable the watchdog timer. N milliseconds = Enable the watchdog timer and set time period (a typical period is tens of seconds). Programming Techniques/Considerations An application may behave correctly, yet it may have one or more threads that become CPU bound for periods of time. In this case, you could periodically give small amounts of time to Windows NT during these periods. This might be needed, for example, to allow Windows NT and Windows 2000 to empty the RS232 UART silo, acknowledge network requests, perform disk I/O, move the mouse pointer, or display something on the GUI. Since the desired behavior can be quite complex, an RTX-defined policy of giving Windows NT time slices may be unnecessary or may interfere with RTSS deterministic behavior. You can easily manage this type of situation by creating a timer handler that periodically suspends the CPU bound thread(s) for short periods of time. Take, for example, an application that runs a thread for 100 milliseconds every second. You could suspend the thread for.5 milliseconds every 10 milliseconds during the 100 milliseconds that it runs. You can create an algorithm, as simple or complex as desired, to support starvation management. Typically, a five percent duty cycle is a reasonable initial setting. You can then use the algorithm to measure and adjust your starvation management. The RTX sample program, starve.c, demonstrates the use of the timer approach. It is located in: c:\program files\vci\rtx\bin\samples\starvation Another approach to starvation management is to simply include calls to Sleep, which should give small amounts of time to Windows NT and Windows 2000 within your application. RTX Power Management for Windows 2000 If there are RTSS processes running on UP system, system power state transitions from working state (S0) to any sleeping state (S1-S5) will be blocked by RTX Power Management. You will see a popup message box telling this fact. However, if there are no RTSS processes running on UP system, such transitions are not blocked. On MP system, system power state transitions from working state (S0) to any sleeping state (S1-S5) will be blocked if RTSS is loaded on one processor. 71

82 72

83 Chapter 5 Performance Overview Real-time systems have exacting performance requirements, including deterministic response times for key operations. This chapter covers the sources of interrupt latency, platformspecific timing factors, and measurement techniques an RTX developer can use to ensure good response times. This chapter contains: Causes and Management of Interrupt Latencies Reducing Your System s Latencies: Tools Overview KSRTM versus SRTM Using KSRTM (Kernel System Response Time Measurement) Using SRTM (System Response Time Measurement) Using RTX Demo (Graphical version of SRTM) Using the Timer Latency Display Tool Using LTP (Latency Test Program) 73

84 Causes and Management of Interrupt Latencies Interrupt latency is of particular concern to real-time systems developers. This topic examines its causes and RTX techniques for managing them. It includes: Software causes Hardware causes Œ Management of interrupt latencies Software Causes Software causes of interrupt latencies include: PIC (programmable interrupt controller)-level masking of interrupts. Windows NT and Windows 2000 kernels and drivers change interrupt masking via HAL IRQL manipulation calls. Drivers routinely mask interrupts for several µs. Processor-level masking of all interrupts. The Windows NT and Windows 2000 kernel, HAL, and special system drivers may mask interrupts for up to 100ms. Œ Interrupt-processing overhead. Hardware Causes Hardware causes of interrupt latencies include: Bus "hijacking" by peripheral devices. For example, a video card may stall the CPU's attempt to read the card's I/O space register. Burst DMA by SCSI controllers. Cache dirtying by Windows NT and applications. Œ Power Management features. Some systems, particularly portables, go to a low-power state after a time-out, and "wake up" with a delay that you can barely notice, but which is intolerable to a real-time application. RTX Management of Interrupt Latencies RTX eliminates PIC-level interrupt disabling by isolating interrupts (through the RTX HAL extension). Windows NT and Windows 2000 and their drivers cannot disable RTSS interrupts. In addition, all Windows NT and Windows 2000 interrupts are masked when RTSS is running. 74

85 Chapter 5: Performance Overview Reducing Your System s Latencies: Tools Overview An RTX developer should be mindful of platform factors. The performance-measurement tools introduced in this topic will help you analyze your system and determine whether it is performing as expected. SRTM (System Response Time Measurement) and RTX Demo SRTM is an RTAPI timer latency measurement tool that measures timer latency observed by an application. Each of the two versions of SRTM, Win32 and RTSS, measures its own environment. An SRTM histogram often shows a characteristic double peak profile: the first peak is a near-) and Using RTX Demo (Graphical version of SRTM). See also KSRTM versus SRTM. best case, the second is the dirty-cache case. The diagram occasionally shows additional "humps" from processor-level interrupt masking. Among the samples is a graphical version of SRTM, RTX Demo, which measures results for both RTSS and Win32. For further details, see Using SRTM (System Response Time Measurement) on page 77. KSRTM (Kernel System Response Time Measurement) KSRTM is a driver and a Win32 utility that measures HAL-level timer latency. Short code paths make it less sensitive to cache jitter than SRTM. It can determine which Windows NT component or device driver is causing the greatest latency event for a real-time application. For further details, see Using KSRTM (Kernel System Response Time Measurement) on page 76. See also KSRTM versus SRTM below. LTP (Latency Test Program) LTP finds misbehaving peripheral devices. This application loops, reading the RTX CLOCK_FASTEST, detecting latency events caused by peripheral activities (such as burst DMA), and reporting instances of latencies exceeding a certain threshold. For further details, see Using LTP (Latency Test Program) on page 82. Timer Latency Display The Timer Latency Display tool performs timing measurements and outputs two displays: Histogram and Latency. For further details and sample outputs, see Using the Timer Latency Display Tool on page 80. KSRTM versus SRTM Both KSRTM (Kernel System Response Time Measurement) and SRTM (System Response Time Measurement) measure timer latencies. While KSRTM provides detailed information about the source of the worst-case latency, it measures only the time to the beginning of the Interrupt Service Routine (ISR). SRTM measures the total time to an RTSS program s timer handler (i.e., a full thread context); it is the more realistic measurement of latencies encountered by RTSS applications. The worst-case SRTM reported latencies range from 35 to 100 microseconds on most Pentium-based systems. 75

86 Using KSRTM (Kernel System Response Time Measurement) Use KSRTM to measure timer response latencies and obtain reports and histograms of the results. This tool exercises the real-time HAL extension, and measures and reports timer response latencies against a synchronized clock. It can present a histogram of such latencies and report which kernel component was running when the longest latency event occurred. It can also provide a list of drivers. KSRTM optionally measures the latencies associated with kernel (DPC-level) and multimedia (user-level) timers. It also allows the timer to drive the sound speaker (a 500- microsecond timer will generate a 1000 Hz square wave). Any timing jitter will produce an audible frequency wobble. Note: KSRTM only works in uniprocessor systems. Usage ksrtm -s 2 Format ksrtm [-r] [-k] [-m] [any of the following flags] seconds_to_sample where -r = Real-time HAL extension timer (default). -k = Kernel (DPC-level) timer. -m = Multimedia (user-level) timer. -h = Histogram of latencies (in addition to summary). -n = No use of real-time priorities. -s = Sound output (square wave driven by timer). -i = IRQL HIGH stalls (test interrupt isolation). -c = Cache flush/dirty and TLB shoot down stalls. -d = Display loaded driver information. -l = Longest latency event information. -u minutes = Minutes between display updates. seconds_to_sample = Duration in seconds to sample timer response latencies. See Also KSRTM versus SRTM 76

87 Chapter 5: Performance Overview Using SRTM (System Response Time Measurement) Use SRTM to measure timer response latencies. By default, this tool generates a 15-second tone and prints a histogram of timer response latencies. You can run SRTM in the RTSS environment to measure RTSS latencies or in the Win32 environment to measure Windows NT latencies. Usage RTSSrun "c:\program files\vci\rtx\bin\samples\srtm" -h -f -s 15 You can also run SRTM using Windows NT Explorer by double-clicking the srtm.rtss icon (for RTSS environment) or the srtm.exe icon (for Win32 environment). Format srtm [-h] [-s] [-1] [-f] seconds_to_sample where -h = Display histogram (in addition to summary). -s = Turn on sound (square wave driven by timer). -1 = Use a 10 ms timer period (default is 1 ms). -f = Use fastest available timer (1 ms or better). seconds_to_sample = Duration in seconds to sample timer latencies. To build SRTM on your system Optionally, you can build SRTM on your system (provided that you have a compiler on it) by entering the following commands at a command prompt: cd \program files\vci\rtx\bin\samples\srtm nmake -f srtm.mak RTSSrun srtm.rtss -f -h -s 5 There should be no compile, link, or make errors. When you run srtm.rtss, you should hear a steady 1 KHz tone for five seconds. See Also KSRTM versus SRTM 77

88 Using RTX Demo (Graphical version of SRTM) RTX Demo graphically illustrates response time latencies in the Win32 and RTSS environments. It measures the total time to an RTSS, Windows NT, or Windows 2000 program s time handle (i.e., full thread context). It is a realistic measurement of latencies encountered by an application. RTX Demo runs an RTSS timer process, a Win32 timer process, or both processes at the same time. It runs the process using either the fastest timer or a 1 ms timer. The timer can also be used to drive a sound speaker. The results are plotted to the graphical area where minimum, average, and maximum latency values are displayed. There are two types of plots: a plot showing the maximum latency values over time and a plot showing the raw data counts of maximum latency values for one sample period. Settings Run Timer As Run an RTSS process, a Win32 process, or both processes at once. The default is an RTSS process. Sound Options Choose to hear sound or not. The default setting is sound enabled. If running both types of processes, you can choose from which process to hear sound. You can also change the sound options while the timer process is running. Timer to Use Choose either the fastest timer available or the 1 ms timer. This option cannot be changed while the process is running. Display Options The Plot option displays graphs in the graphical output area. The default setting is plot enabled at the start of a run. The Data option writes latency values to the data area. The default setting is data enabled at the start of a run. You can change these options while the process is running. Max Latency Y-axis Scale This option is used with the Run Max Latency action only. The selectable values for the plot's y-axis scale are 100 ms, 1000 ms, and 10,000 ms. The default is 100 ms. You cannot change this selection during data retrieval. This option is disabled when running the histogram option. Actions Run Max Latency Plots the maximum and average latency values at one-second intervals. RTSS process results are plotted in cyan, Win32 results in red. The minimum, average, and maximum latency values are recorded in the data area. Run Histogram Plots the number of latency values occurring within 1 ms intervals. RTSS process results are plotted in cyan, Win32 results in red. The minimum, average, and maximum values are recorded in the data area, along with the raw data for the histogram. Stop Stops the process. Add Load Simulates a disk load on the system in order to show more accurately the maximum latency times on a busy system. The load consists of a creating a file and writing to it repeatedly with no buffering. 78

89 Chapter 5: Performance Overview Remove Load Stops the "load" process. Exit Terminates the program. To run RTX Demo 1. Start RTX Demo using one of these methods: Choose RTX Demo from the RTX menu, or Open the tool from the following directory: c:\program files\vci\rtx\bin\samples\rtxdemo 2. Select the type of process to run and which type of timer to use. 3. Click on either Run Max Latency or Run Histogram. 4. Once the process is running, you can change sound, plot, and data options. You can also click: Stop to terminate the SRTM process. Add Load (if enabled) to simulate a disk load, and then Remove Load to stop it. Exit to terminate RTX Demo. Interpreting the Max Latency Plot 57;'HPR0D[/DWHQF\YLHZ The x-axis shows time in seconds. The y-axis is the response time latency in microseconds. The solid line plots the maximum latency value in microseconds during a one-second interval. The dashed line plots the average latency value. The x-axis shows time in seconds. The y-axis is the response time latency in microseconds. The solid line plots the maximum latency value in microseconds during a one-second interval. The dashed line plots the average latency value. The data area records the minimum, average, and maximum latencies for the interval. It also shows the greatest maximum value over the course of the data retrieval (from clicking on the Run Max Latency button until clicking on the Stop button). RTSS latency values are shown 79

90 in cyan, Win32 values in red. When Win32 values are too high, they are plotted at the upper boundary of the window. Interpreting the Histogram Plot The x-axis shows response time latency in microsecond intervals. The y-axis shows a count from 0 to 2000 when using the fastest timer, 0 to 100 when using the 1 ms timer. The histogram shows the number of latencies that fell within a particular microsecond interval. The raw data for the histogram is written to the data area, along with the minimum, average, and maximum values. The data is refreshed every second. RTSS latency values are shown in cyan, Win32 values in red. Using the Timer Latency Display Tool The Timer Latency Display tool consists of: A control and presentation application, which runs as an ordinary Windows NT task ΠAn RTSS application, which performs the timing measurements These two tasks communicate through shared memory. The RTSS task is similar to SRTM. The main execution thread creates an RTX timer, and sets it to expire periodically at the fastest available timer rate. The thread then enters a loop, testing a terminate request flag in shared memory, and sleeping between tests. The timer function, which is called by RTSS each time the timer expires, reads the RTSS system clock, and computes the difference between the time observed, and the requested scheduled time. A histogram of this difference is compiled in shared memory. The RTSS task also accumulates shortest and longest observed latencies. Settings Enable Sound The timer function toggles the output state of the system speaker port each time it is called. Since the timer function is called periodically, this results in a tone with a 80

91 Chapter 5: Performance Overview period equal to one half of the timer setting value. The system timer is set to 1 ms in the demo, resulting in a 500 Hz tone. Histogram View the data as an accumulated histogram. Latency View a time sequence of minimum, maximum, and average values observed in a series of 1-second intervals. Actions Reset Reset accumulated statistics. To run the Timer Latency Display tool 1. Open the following directory: c:\program files\vci\rtx\bin\samples\latencydisplay 2. Double-click NtRTSS.rtss to start the timer program. The program starts with the sound enabled. 3. Double-click the display program, RTSSDisplay.exe. You can change settings for sound and view while the timer program is running. 4. Follow these steps, as appropriate: To end the program Terminate the client process and then exit from the display process. To end the display process Click the X button at the far right of the title bar. To terminate the timer process Obtain the RTSS Process ID and then kill the process by typing the following command at a command prompt: RTSSkill To obtain a list of the current RTX processes Find the PID associated with NtRTSS.rtss and then type: RTSSkill ### (where ### is the PID). Interpreting the Histogram Timer Latency Display: Histogram view (Recorded on Gateway G MHz Pentium) The horizontal axis represents the time difference between scheduled and observed time, in microsecond units. The vertical axis represents a count of the number of times this difference 81

92 is observed to fall within a particular range, or bin. Counts are displayed on a logarithmic axis. The histogram bin size is adjusted automatically to ensure that the highest observed latency value is visible on the graph. Interpreting the Latency display Timer Latency Display: Latency view (Recorded on Gateway G MHz Pentium) The Latency view selects presentation of a time sequence of minimum, maximum, and average values observed in a series of one-second intervals. Latency is plotted on the vertical axis. The horizontal axis is set to display the results accumulated over the past one-minute interval. A bright green vertical bar sweeps from left to right, illuminating the current second. Using LTP (Latency Test Program) Use LTP to find misbehaving peripheral devices. This tool counts the number of instances in a given period of time that the time between clock reads exceeds a threshold value, using approximately 20% of the CPU time for the duration of the test. The latency is expected to be two to five microseconds. Higher latencies probably indicate non-cpu related blocking. Usage RTSSrun ltp -h Format ltp [-t <num>] [-s <num>] where -t <num> = Watch for latencies greater than this number of microseconds; the default is 10 microseconds. -s <num> = Run the test for this number of seconds; the default is 20 seconds. -h = Display message 82