Real-Time Operating Systems and Middleware

Important Announcements:

• There will be a lesson on Thursday November 24th in "Aula Garda" (DISI department) from 9 to 11.

The Course:

The course web page changed: here is the old (2014) page

Slides:

Theory:

• Introduction to the course
• Real-Time Scheduling
• Real-Time Scheduling Analysis
  • Exercizes
• Shared Resources
• Scheduling with dynamic priorities
• Some notes on implementing scheduling algorithms. For fixed priorities, check kernel/sched/rt.c in the Linux kernel (functions pick_next_rt_entity(), __enqueue_rt_entity and __dequeue_rt_entity).
• Removing some restrictive assumptions
  • A reservation-based scheduling algorithm
  • MultiProcessor real-time scheduling
  • The Sporadic Server
• EDF scheduling in Linux
  • Something more on Real-Time Scheduling algorithms
• Summary about OS kernels
• The Timer Resolution Latency
• The Non-Preemptable Section Latency
• The Real-Time OS Kernels
  • Some slides about Linux Kernel Locking (enforcing consistency in a modern multithreaded kernel).
  • A paper about Real-Time on Linux
• Putting everything together, to implement real-time applications
• Example of real-time application in a dual-kernel system, using xenomai

Practice (in the lab):

• Real-Time API - Part I
• Real-Time API - Managing the Concurrency
• The PThreads API
  • Introduction to PThreads
  • PThreads Synchronization
  • Example about pthreads and mutexes
• Compiling for embedded systems:
  • Scripts (try these on newer systems) for generating an embedded FS
  • A version of busybox that used to compile without issues on the computers in the lab
  • A version of busybox that should be better now, with its configuration file
  • Package containing a kernel for the generated FS
  • How do the script work:
    • Some notes on CrossCompilers
    • How to build a filesystem for embedded devices
    • Filesystems for embedded devices: a summary
• Tutorial on writing real-time applications with POSIX
• Source code for an example RT application
• The Some slides about the Linux Kernel

NOTE: slides are periodically updated... Be sure to have the latest version!

For comments, qestions, etc. send me an email.

Captain's log:

TBD

References:

• A good Operating System book (I suggest ``Operating Systems'' by William Stallings, but ``Operating Systems Design and Implementation'' by Andrew Tanenbaum, or similar books are OK too). As an example here is a list of the interesting chapters in ``Operating systems. Internals and design principles; 7th ed.'' by W. Stallings.
• For the Real-Time Scheduling part, interested students can consult ``HARD REAL-TIME COMPUTING SYSTEMS: Predictable Scheduling Algorithms and Applications'' by Giorgio Buttazzo (Springer, 2005) - There is an italian version of the book, too.
• For the Real-Time programming part, consult the Open Group site (in particular, have a look at the real-time extensions)
• Another good reference for people interested in Unix programming is ``Advanced Programming in the Unix Environment'' by W. Richard Stevens (Addison Wesley)

Funny Stories:

• About the Mars Pathfinder

Projects:

A preliminary list of possible projects for the exam is available. Email me if you have questions

Other Material:

• Some notes about C Coding
• Some notes about writing Makefiles
• For experiments on operating system kernels, the qemu emulator will be used. If you are impatient and you want to start playing with the emulator now, here you can find version 1.7 precompiled and ready to be used on a Linux system. Just download the tarball and uncompress it in /tmp. Have a look at the qemu site for instructions about how to use it.
• A cross-compiler for ARM
• A newer version, that should be able to run on the computers of the lab. To use it:
  • Uncompress somewhere (say, in "/tmp"): "tar xvf cross-arm.tgz"
  • The target files are in "cross-arm/sysroot", while the host tools are in "cross-arm/toos"
  • Do: "export PATH=$PATH:/tmp/cross-arm/tools/bin"; "export LD_LIBRARY_PATH=/tmp/cross-arm/tools/lib"
• A patched version of busybox that works on the computers in A104
• The package containing the ARM test kernel
• Some scripts for generating an initramfs
• A newer version that works with the new cross-compiler and should work in the lab
• The kernel headers for compiling test Linux modules (for ARM)
• How to use xenomai
• Example about Linux Kernel Modules, and some instructions for compiling and using kernel modules.

Some Practice at the Computer...

If you want to see how the theory studied in the course applies in simple programming exercizes, check this link.

The Exam

Are you ready?

The texts of some of the previous exams:

• January 18 2011
• February 15 2011
• June 7 2011
• July 19 2012
• September 14 2012
• January 15 2014

Remember to send me your projects some days in advance respect to the exam, so that I can evaluate them.