RT linux
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RTLinux is a real-time operating system that allows real-time applications to run on top of Linux. It modifies the Linux kernel to add a virtual machine layer with a separate task scheduler that prioritizes real-time tasks over standard Linux processes. This enables RTLinux to support hard real-time deadlines. Programming in RTLinux involves creating modules that can be loaded and unloaded from the kernel using specific commands. Real-time threads and synchronization objects like mutexes are implemented using POSIX interfaces.
RT linux
- 1. OVERVIEW OF RTLINUX & FEATURES Dr. C. SARITHA Lecturer in Electronics SSBN Degree & PG College Anantapur
- 2. OVERVIEW • What is operating system? • Real time operating system • Overview of Unix/Linux • Features of Linux • RTLinux
- 3. What is an operating system? • An operating system is a set of programs that manage computer hardware resources and provide common services for application software. • The operating system is the most important type of system software in a computer system. • A user cannot run an application program on the computer without an operating system.
- 4. Types of Operating Systems Different types of operating systems are • Real time • Multi user • Multi-tasking vs -Single-tasking • Distributed • Embedded
- 5. Real-time Operating System • A Real-time operating system is a multitasking operating system intended for applications with fixed deadlines. • Applications include some small embedded systems, automobiles engine controllers, industrial robots, spacecraft, industrial control, and some large-scale computing devices.
- 6. Most widely deployed Real-time operating system are • Linux • OSE • QNX • RTLinux • VxWorks • Windows CE
- 7. Categories Of Real-time Systems There are two flavors of real-time systems. • Hard Real-time System • Soft Real-time system.
- 8. • Hard real-time system is hardware or software that must operate within the confines of a stringent deadline. • The application may be considered to have failed if it does not completes its function within the allotted time span. • Hard real time systems include aircraft control systems. • In soft real-time systems, meeting the deadline is important but missing the deadline will not lead to a catastrophe.
- 9. Overview of Unix/Linux • Unix stands for UNiplexed Information and Computing • Unix was developed by Ken Thomson and Dennis Ritchie beginning 1969.It became the popular operating system in the academic community during 1970’s. • It was commercialized in and since then ,its use in both academic and commercial world has grown tremendously.
- 10. • Unix operating systems are widely used in servers, workstation, and mobile devices. • Unix was designed to be portable, multi- tasking and multi-user in a time- sharing configuration. • Unix operating systems are not open source operrting systems.
- 11. The main attractions of Unix are: • Most of the operating system was developed in a high level languages. This was revolutionary during those days because before advent of UNIX ,operating system were developed in assembly languages. • The main attraction of Unix is that provide a large number of utilities for software debuggers, source code control systems.
- 12. Unix has some popular myths: • It is a complicated operating system. • Too many options for each command. • Too many commands and utilities. • Unix was not free and open source it is commercial operating system.
- 13. • In April 1991, Linus Torvards, a 21-year- old student at the University of Helsinki, Finland started working on some simple ideas for an operating system. • Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. • Linux is the kernel of the operating system.
- 14. • Linux was originally developed as a free operating system for Intel x86-based personnel computers. • Linux since has been ported to more computed hardware platforms than any other operating systems. • Linux also run on embedded systems. Such as mobile phones, network routers, televisions.
- 15. Features of Linux • Linux is a multi-user operating system. Every user is given a username or login name. • The heading system is organized hierarchically. At the topmost level is the root directory denoted by / under which there will be sub-directories. Under each subdirectory there can be directories or files.
- 16. Important directories are • /bin contains commonly used commands • /usr/bin contains less commonly used commands • /etc contains the system administration commands • /dev contains device files • /usr /spool/mail contains mail files.
- 17. A variety of user interfaces are available. • The command user interfaces are shell, k- shell, and C shell. X-windows provide the graphical user interface. • To provide security for user’s files, a user will have a password. • Every file is given protections read, write and execute permissions are given to the owner, group and others.
- 18. KERNEL: • Kernel manages the tasks to achieve the desired performance of the system . • To manage the tasks, the important requirements are to schedule the tasks and to provide inter-task communication facilities • to achieve these two requirements, kernel objects are defined such as
- 19. • Tasks • Mutexes • ISR’s • Events • Message boxes • Mailboxes • Pipes and timers • Kernel provide the memory management service, time management services, interrupt handling services and device management services.
- 20. LINUX KERNEL Users Users Users Users processors processors processors processors System libraries Device drivers Unix/Linux kernel hardware
- 21. RTLINUX • RTLinux is a hard real-time RTOS microkernel that runs the entire Linux operating system as a fully preemptive process. • It was developed by Victor Yodaiken, Michael Barabanov and others at the New Mexico Institute of Mining and Technology and then as a commercial product at FSMLabs. • FSMLabs has two editions of RTLinux.
- 22. • RTLinux pro and RTLinux free. RTLinux pro is the priced edition and RTLinux is the open source release. • RTLinux support hard real time applications, the Linux kernel has been modified by adding a layer of software between the hardware and the Linux kernel. This additional layer is called “virtual machine”. • A foot print of 4MB is required RTLinux.
- 23. • The new layer, RTLinux layer has a separate task scheduler. This task scheduler assigns lowest priority to the standard Linux kernel. Any task that has to met real-time constraints will run under RTLinux. • Interrupts from Linux are disabled to achieve real-time performance.
- 24. RTLINUX KERNEL Users Users Users Users processors processors processors processors System libraries RTlinux kernel Device drivers Unix/Linux kernel hardware
- 25. DIFFERENCESS BETWEENTHE LINUX AND RTLINUX: Linux RTLinux • Linux is not a hard real time system. • RTLinux supports hard real-time • The tasks, which applications. do not have any time constraints. • Any task that has real-time constraints will run under RTLinux.
- 26. In RTLinux location of the various files are: • RTLinux will be installed in the directory /usr/rtlinux-xxx, where xxx is the version name. • /usr/rtlinux/include contains all the include files necessary for development project. • /usr/doc/rtlinux/man contains the manual pages for the RTLinux. • /usr/rtlinux/modules contains the core RTLinux modules
- 27. The two important aspects while doing programming in RTLinux are: • By default, the RTLinux tasks do not have access to the computer’s floating points unit. Hence need to explicitly set the permissions for every RTLinux task. • Cannot pass arguments from the command prompt.
- 28. RTLINUX MODULES • RTLinux programs are not created as stand-alone units, they are created as modules, which are loaded into the Linux kernel space. • The C source files are compiled into objects files using the gcc command with the argument –c flag. In the C file, the main() function gets replaced with the fallowing lines:
- 29. • Int init_module(); • Void cleanup_module(); • Init_module is called when the module is first loaded into the kernel. • This function returns 0 if the module is successfully loaded. It returns a negative value in case of failure. When the module is loaded is to be unloaded , the cleanup_module() is called.
- 30. EXECUTING THE RTLINUX MODULES • In RTLinux load and stop user modules using the RTLinux command. Using this command we can obtain status information about RTLinux modules. • The command syntax is: • $rtlinux start my_program • $rtlinux stop my_program • $rtlinux status my_program
- 31. CREATING RTLINUX POSIX THREADS • A real-time program generally consists of a number of threads. • Each thread share a common address space . • Pthread_create() function is used to create a new real-time thread. The corresponding header file is #include <pthread.h>
- 32. • To achieve real-time performance. The various POSIX compliant API function calls are used. These function calls are related to create and cancel semaphores. • To implement mutex, we have to include the header file <rtl_mutex.h> in the C program. • To cancel a thread, the system call is pthread_cancel.
- 33. TIMER MANAGEMENT • A number of internal clocks are available in RTLinux to manage the timers. • To obtain the current clock reading using command is: clock-set time() function clock_id gives the identification of the clock to be read.