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8/9/2019 vxworks and embedded linux.ppt
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VxWorksVxWorks
1
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Topics CoveredTopics Covered
What is Real Time Operating System (RTOS)
Standard for RTOS
VxWorks Features as RTOS
Layer Struture
!irokernal Funtions"
!ultitasking
Sheduling
#nterrupt Ser$ie %ode
Shared %ode and Reentrany
#ntertask %ommuniations
&ppliations for VxWorks
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What is Real Time OS (RTOS)What is Real Time OS (RTOS)
RTOS Characteristics
'roessing must e done ithin a time onstraint or thesystem ill fail*
&ll delays in the system ill e ounded+ from the retrie$al of
stored data to the time RTOS finishes the re,uest*
Types of RTOS
-ard RTOS
Soft RTOS
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Standard for RTOSStandard for RTOS
Standard re,uirement for RTOS
'OS#. /001*/ y #SO2#333 hapter*
&synhronous #2O
Semaphore
!essage ,ueues
4ueued signals
Sheduling %loks and timers
!emory management
'OS#. interfaes"
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Layer StructureLayer Structure
Real5Time 3medded &ppliation
6raphis !ultiproessing #nternet
7a$a Support 'OS#. Lirary File System
Wind8et 8etorking
Wind Microkernal%ore OS"
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Schedulin!" One C#$Schedulin!" One C#$
'riority5ased preempti$e sheduling
3ah task has priority (from 0 5 highest to ABB 5loest)* 3ah priority has its on ,ueue*
#f to tasks are in the ready state< a loer priority taskould e pre5empted y one of a higher priority*
Round5roin sheduling
&fter time slie for a task expires< another task ith the
same priority ill exeute during the gi$en time slie*
'reemption loks
These loks pre$ent task ontext sithing< ut do notpre$ent interrupt handling*
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%nterrupt Service Code%nterrupt Service Code
Via interrupts< the system is informed of externale$ents*
#nterrupt Ser$ie Routines (#SRs) run outside anytask ontext*
#nterrupt handling in$ol$es no task ontext sith*
Limitations of #SR"
&ll #SRs share the same stak
#SR has no ontext that an e suspended
%annot take the semaphore< ut an gi$e thesemaphores< releasing any task aiting on them*
%annot perform #2O through dri$ers exept pipe*
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Shared Code and ReentrancyShared Code and Reentrancy
Shared Code5 a single opy of ode exeuted y multipletasks*
Shared %ode must e reentrant* & suroutine is reentrant if asingle opy of the routine an e alled simultaneously fromse$eral task ontexts ithout onflit*
Reentrany Tehni,ues"
9ynami Stak Variales 6loal and Stati Variales 6uarded y Semaphores
Task Variales
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Shared Code and Reentrancy" ContinuedShared Code and Reentrancy" Continued
Task/( )C D**
omFun(my9ata/)
E
TaskA( )C D**
omFun(my9ataA)
E
omFun(your9ata)CE
my9ata/
my9ataA
9ynami Stak Variales
Tasks Task Staks %ommon Funtion
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Shard Code and Reentrancy" ContinuedShard Code and Reentrancy" Continued
6uarded 6loal and Stati Variales
Mutual-exclusionmehanism 5 only one task at a time
an e in a ritial setion of the ode*
Task Variales
Four yte $ariales are added to the task ontextlok (T%@)*
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%ntertask Communications" One C#$%ntertask Communications" One C#$
Shared 9ata
!essage 4ueue
'ipes 5 Virtual #20
8etork #ntertask %ommuniation
Sokets
Remote 'roedure %all
Types of #ntertask %ommuniations"
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%ntertask Communication" Shared &ata%ntertask Communication" Shared &ata
&ess Shar9ata
&ess Shar9ata
Tasks !emory
&ess Shar9ata
Shar9ata
/*
A*
1*
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SemaphoresSemaphores
Semaphore 5 mehanism for mutual exlusion and intertaskommuniation*
@inary Semaphore
Semaphore
a$ailale
TimeOut=
8oWait
Task ispended fortimeOut
Task ont*
Semaphore
taken
8O8O 8O
G3S
Task ont*
Semaphore
not taken
G3S
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Semaphores" ContinuedSemaphores" Continued
#s semaphore is gi$en and no tasks areloked< ount >>
%ounting Semaphore
3$ery time is semaphore is gi$en ount >>
3$ery time is semaphore is taken ount 55
#f ount=0< task that tried to take semaphore is loked #f semaphore is gi$en and task is loked< task isunloked
Speial Semaphore Option (8ot in 'OS#.)
Timeout
Time the task is illing to ait (time in tiks) in pended
state* #f time H timeout< 3RROR ours*
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%ntertask Communication" essa!e%ntertask Communication" essa!e'ueue'ueue
&llos a $ariale numer of messages to e ,ueued
&ny task or #SR an send a message to a ,ueue*
!ultiple tasks an send and reei$e from the samemessage ,ueue*
Timeout 'arameter"
Send message" ho long to ait for uffer spae
to plae message*
Reei$e message" ho long to ait to otainmessage*
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pplications for VxWorkspplications for VxWorks
Flight simulators
Radio and optial telesopes
8a$igation systems
9eep sea instrumentation
Traffi ontrol systems
!odems
D any systems here rigid time re,uirement ha$e eenplaed on the operation of a proessor or the flo of the data*
Some usage of RTOS
'rinters
9igital ameras
-and5held omputingde$ies
Routers< sithes< andother netork de$ies
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Commercial m*edded LinuxCommercial m*edded Linux
+eo,are +eoLinux
Red -at derived for informationappliances
#alm#alm Tynux%nternet appliuance and multimedia
Red -at m*edded Linux
!eneral purpose em*edded solution
RedSonic Red.%ce Linux
runs from &iskonChip orCompact/lash
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Commercial m*edded LinuxCommercial m*edded Linux
Rid!eRun &S# Linux
for multimedia" ,ireless" RT on &S#
TimeSys Linux 0#L
lo, latency enhanced kernelTuxia TST
distro tar!ets %nternet appliances
Vital Systems vLinuxfor R *ased em*edded apps
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Open Source m*edded LinuxOpen Source m*edded Linux
m*edded &e*ian #ro1ect
convert &e*ian to an em*edded OS
TLinux
for #C234 S5C6s
uCLinux
for microprocessors that don6t have
uLinux (muLinux)distro fits on a sin!le floppy
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Commercial Linux RTOSCommercial Linux RTOS
/SLa*s . Open RT Linux
Lineo . m*edix Realtime
LynuxWorks . 5lueCat RT
ontaVista Soft,are . Real Timextensions
R&Sonic . R&%C Linux
TimeSys . Linux7Real.Time
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Open Source Linux RTOSOpen Source Linux RTOS
RT Linux . real time extension *ased onRTLinux
8$RT . event schedules ,ith 23us resolution
Linux.SRT . for soft real time apps likemultimedia
'linux . provides 'uality of Service !uarantees
RT% . 9hard: Real Time pplication %nterface
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RTLinuxRTLinux
9hard real.time: mini operatin! system
runs Linux as it6s lo,est priority executionthread
Linux thread completely preempti*le
Real time threads and interrupt handlersnever delayed *y non.realtime operations
Supports user level pro!rammin!
iniRTL implementation fits on a floppy
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What6s so special a*out Linux;What6s so special a*out Linux;
ultiple choices vs< sole source
Source code freely availa*le
Ro*ust and relia*le
odular" confi!ura*le" scala*le
Super* support for net,orkin!and %nternet
+o runtime licenses
Lar!e pool of skilled developers
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What6s so special a*out Linux;What6s so special a*out Linux;
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What6s special a*out Open Source;What6s special a*out Open Source;
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