Course 101: Lecture 2: Introduction to Operating Systems

May 20, 20152 likes668 views

This lecture goes into an introduction to the role and functionality of operating systems in Embedded Systems and in computer systems in general Check the other Lectures and courses in http://Linux4EnbeddedSystems.com or Follow our Facebook Group at - Facebook: @LinuxforEmbeddedSystems Lecturer Profile: Ahmed ElArabawy - https://www.linkedin.com/in/ahmedelarabawy

Linux For Embedded Systems
ForArabs
Ahmed ElArabawy
Course 101:
Introduction to Embedded Linux

Lecture 2:
Introduction to Operating Systems
for Embedded Platforms

Operating Systems …..
• What the end user sees is just the Operating System frond end
user interface (Desktop)
• Behind the scene there is the KERNEL
• The Kernel runs a lot of functionality in the background and
performs a lot of tasks for the user and the developer, and
abstracts a lot of HW details

Embedded System Structure
Hardware device (processor, memory, storage, peripherals)
Initialization
(bootloader)
Operating System
(Linux Kernel)
Device drivers
ApplicationUtilities
C Library

User Management
• The kernel supports multiple users using it
• Each user has his own resources and privileges
• There is the super-user (root/admin) that have full control on the
system
• User privileges decides his rights on his owned resources and other
users resources
• The kernel manages user privileges and protects each user resources
from unauthorized access by other users
• The kernel manages also the system environment for each user

Process Management
• The kernel enables the system to run multiple applications
(processes) at the same time
• Each Application thinks that it owns the whole system
• Each process may even have multiple threads that run
simultaneously
• The kernel has a SCHEDULER that provides time slots to each
process/thread in a pre-determined order to enable multi-tasking
• The order of time slot assignment and the time slot size is based on
the SCHEDULING ALGORITHM

Process Management
ProcessSchedulingAlgorithm
• There are multiple scheduling techniques:
• Round robin
• Priority Based
• Processes may block on events such as hardware job
completion, other process will take the processor cycles

Process Management
Preemption
• The scheduler can be:
• Pre-emptive
• A higher priority task can interrupt the low priority task before it
completes its job
• Non-preemptive
• Once a process takes control, it has to finish its job before it releases
control

Memory Management
• When the processor is running multiple processes, each process will
need to have its own memory
• The kernel works with the Processor to provide two functionalities:
• Memory Protection (MPU)
• Protects each process memory from being corrupted by the other
processes
• Memory Management (MMU)
• Each process will think that it owns all the system memory

File-System Management
• The kernel performs jobs related to handling of storage
devices
• It gives the applications the feel of files and directories and
hide the hardware details behind all of that

Power Management
• The kernel handles power related functionality such as:
• Managing sleep modes of the processor
• Adjusting the processor clock rate based on its load

I/O and Interrupt Handling
• Processor is connected to several I/O devices
• Those devices may use Interrupts to get the processor/kernel
attention
• Kernel handles the interrupts received from Input/Output devices

Timers and Time Related Tasks
• The Processor is interrupted per time tick
• Kernel uses this interrupt to keep track of time
• Tick duration defines the time resolution for the kernel/system
• Kernel is responsible to keep track of time:
• Handle timers
• Handle time of day clock
• Handle deferred jobs

Networking and Communication
• The kernel is responsible to enable communication via:
• Wired / wireless networking
• USB/SDIO/Serial/…
• Other communication means

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