RTOS LINUX2.6.X & LINUX2.6.24

1. RTOS
LINUX2.6.X & LINUX2.6.24
BY:
J.SUDARSHANREDDY
ROII NO:117Y1A0425
1/25/2015J.SUDARSHANREDDY

2. TOPICS:
 INDRODUCTION
 REAL TIME LINUX FUNCTIONS
 LINUX HAS THE FOLLOWING FEATURES
 LINUX MODULES
 LINUX FUNCTIONS FOR THE SIGNAL,MULTITHREADING,SEMAPHORE AND MESSAGE QUEUE
INTERPROCESS COMMUNICATION
1/25/2015J.SUDARSHANREDDY

3. INTRODUCTION:
 Linux is increasingly used in embedded systems and real time enhancements of that
introduced As linux2.6.x
 The linux provide preemptive scheduling , high resolution timers and preemptive
interrupt service threads
 Linux latest version is linux 2.6.24 ,released in January 2008
 Reasons for the popularity of linux OS are that it is a freeware, device driver
feature,expandability of the kernel codes at runtime and has provision of registering
and deregistering device driver modules
 The modules are scheduled like the process Sections 10.3.1 and 10.3.2.

1/25/2015J.SUDARSHANREDDY

4. Real time linux functions :
 The os named linux is after linus Torvalds ,father of the linux os
 Embedded linux systems combine the linux kernel with a small set of free software
utilities
 The glibc is often replaced as the C standard library by less resource consuming
alternatives such as dietlibc ,uclibc or newlib
 Embedded linux application program makes the systems calls for the functions at a
kernel
 1.process management
 2.memory management EX (allocation,delocation )
 3.file system
 4.shared memory
 5.networking systems functions
 6.device control functions for any peripheral present into a system
 7.graphic editors for kernel configuration
 8.soft realtime scheduling
1/25/2015J.SUDARSHANREDDY

5.  The following are the three important classes of
devices in embedded linux:
 1.realtime linux scheduler has all functions as 0(1)functions:
Which means that size of input to a function and function run time are linearly correlated.
 2.the task scheduler supports spin lock (section 7.11) :
It is a preemptive scheduler.
 3.linux supports characters and block devices:
A device type can be a char device for example a parallel port , lcd matrix .
 The character acess is byte to byte and analogous to the access from and to a printer device.
 Systems call functions are also like an I/O device open (), close () write (), read (), functions.
1/25/2015J.SUDARSHANREDDY

6.  Linux has the following features useful for embedded system
design:
 1.linux is multiuser OS and supports user groups
 2.linux has root directory (represented by /sign)
 3.linux has large number of editor,file,directory,I/O commands .Each command can
Consists of a number of words .First word is command and remaining words are arguments .
 4. Linux has number of interfaces for users .For example X-WINDOWS for GUI and csh
 5.Process always creates as child process in the process that uses fork()function
 6.linux has modules for the character,block,socket,network device drivers and linux 2.6.x
Support 4095.
 7.Linux supports a module initialization,handeling of errors,prevention of un authorized port acess,
 8.The linux OS supports registering of the driver configuration and functions
 9.The linux kernel use of sequential acess ,specific memory address only by the registering
and de registering mechanisam.
1/25/2015J.SUDARSHANREDDY

7. Registering and de registering and related
functions of linux modules :
 init :
 Insmod:
 Rmmod:
 Cleanup:
 Register-
capability:
 Unregister
capability:
 Register
symtab:
The init module()is called before the module is inserted into the kernel
Inserts module into the linux kernel the object file module 1.0,inserts by
Command and insmod module 1.0
A module file module 1.0 is delated from the kernel by command and
rmmod module1.
A kernel level void function,which perform by action on an rmmod call from
the execution module .
A kernel level function for registering
A kernel level function for de register
A symbol table function support ,which exist an alternatively to declaring
functions .
1/25/2015J.SUDARSHANREDDY

8.  Linux has following feauters useful for
embedded system design:
 1.Linux 2.6.x all tasks are assigned static priorities between -19 to +20 .time
slicies are varied as per priority
 2.Realtime linux 2.6.24 a latest realease supports a new set of group scheduling
functions,Which improves cups load
 3.Linux 2.6.24 provides high resolution timers as well as tick less timer
 4.Linux 2.6.24 supports functions to improve system performance by restricting
the block device from teaking larger cu load
1/25/2015J.SUDARSHANREDDY

9. Linux functions
Features
 1.thread properties:
 2.signal functions:
 3.thread functions:
 4.Semaphore
functions
 5.Mutex functions
Description
1.Threads of same process share the memory space and manage acess
premises
1.Struct sigaction signal 1;/*statement in c defines a struacture signal1 .*/
Signal1 .sa-flags=0;/*sets flags=0*/
1.Pthread-self();/*reaturns gets id of the function pthread-self calling
thread self */
2.();/*sends ‘kill’ signal to the thread*/
1.Sem-wait (&sem1);/*wait for the semaphore sem1*/
2.Sem-post (&sem1)/*post the semaphore sem1*/
1.Pthread –mutex-lock();the argument is mutex ms1or ms2 or other*/
2.Pthread –mutex-unlock();the argument is mutex ms1or ms2 or other*/
1/25/2015J.SUDARSHANREDDY

10. THANK YOU
1/25/2015J.SUDARSHANREDDY