uCOS-II Kernel Structure

uCOSII Kernel Structure936317 許哲宇 936719 丁俊宏

uCOSII KernelMemory Management

OUTLINE Introduction Kernel Structure Overview Mutual Exclusion Task Management Interrupts Clock ticks uCOSII initialization

Introduction microCOS-II The Real-Time Kernel is a highly portable ROMable very scalable preemptive real-time multitasking kernel (RTOS) for microprocessors and microcontrollers microCOS-II can manage up to 63 application tasks Over 100 microprocessor ports are available to DOWNLOAD Reference httpwwwucos-iicom Jean J Labrosse

About microCOS-II

Structure Overview

Mutual Exclusion Critical sectiondisable interrupt OSSchedLock()disable scheduling OSSemPend()semaphore

Critical section Critical Section

Shared resource region should implement mutual exclusion

Disable InterruptOS_ENTER_CRITICAL()

Enable InterruptOS_EXIT_CRITICAL()

Defined in OS_CPUH

void Function(void) OS_ENTER_CRITICAL() Operate shared data OS_EXIT_CRITICAL()

OSSchedLock()void Function (void) OSSchedLock()

You can access shared data in here (interrupts are recognized)

OSSchedUnlock()

OSSemPend() OS_EVENT SharedDataSemvoid Function (void) INT8U err OSSemPend(SharedDataSem 0 amperr) You can access shared data in here (interrupts are recognized) OSSemPost(SharedDataSem)

Task Management Task introduction Task format Task scheduling

Task introduction Task is a single instance of program Task thinks it has all CPU control itself Task has its own stack and own set of CPU registers backup in its stack Task is assigned a unique priority (highest 0 ~ lowest 63) Task is an infinite loop and never returns 1048698 Task has states microCOS-II saves task records in Task Control Block(TCB)

Task format Task is an infinite loop Return type is void because nothing

will be returned Parameter is a void pointer type so

that you can pass anything you want

void YourTask (void pdata) for () User Code Text uCOS-II System Call User Code Text

OSMboxPend() uCOS-II System Call OSQPend() OSSemPend() OSTaskDel(OS_PRIO_SELF) OSTaskSuspend(OS_PRIO_SELF) OSTimeDly() OSTimeDlyHMSM()

Task scheduling Task State Transfer Diagram (TSTD) Task Control Block (TCB) Task Scheduler Task Pending Task Creation Task Deletion

TSTD

diams Running ndash task has control of the processor and executing its job diams Ready ndash task is ready to execute but its priority is less than the running task diams Waiting ndash task requires the occurrence of an event to continue diams ISR ndash task is paused because the processor is handling an interrupt diams Dormant ndash task resides in memory but not seen by the scheduler

TCB A TCB contains task stack pointer priority

number delay time value task state and some useful information for this task

OSTCBStkPtr OSTCBExtPtr OSTCBStkBottom OSTCBStkSize OSTCBOpt OSTCBId OSTCBNext OSTCBPrev OSTCBEventPtr OSTCBMsg OSTCBDly OSTCBStat OSTCBPrio OSTCBX OSTCBY OSTCBBitX OSTCBBitY OSTCBDelReq

TCB (cont)StkPtr ExtPtr StkBottom StkSize Opt Id Next Prev EventPtr Msg Dly Stat Prio X Y BitX BitY DelReq

Stack

Event Msg

NextPrev NextPrev NextPrevOSTCBList

00

Delay timeState

Delete request

Priority information

TCB (cont)

OSTCBFReeListOSTCBtbl[OS_MAX_TASKS+OS_N_SYS_TASK]

Task Scheduling amp Context Switch In microCOS-II task scheduling if performed on following conditions diams A task is createddeleted diams A task changes state minus On interrupt exit minus On post signal minus On pending event minus On task suspension If the scheduler chooses a new task to run context switch occurs

Task Scheduler Preemptive Kernel Not support time quantum

Task Scheduler (cont) Principle select the highest priority

task from Ready List How to select the priority task from a

Ready List

Ready List PriorityGet the highest priority

Modify priority state

Double-linked List with

priority field

TASK 1

NEXTPREV

Priority

TASK 2

NEXTPREV

Priority

TASK 3

NEXTPREV

Priority

TASK 4

NEXTPREV

Priority0

0OSTCBList

Task Scheduler (cont)TASK 1

NEXTPREV

Priority

TASK 2

NEXTPREV

Priority

TASK 3

NEXTPREV

Priority

TASK 4

NEXTPREV

Priority0

0OSTCBList

Method 1Get the highest priority

Modify priority state

Get the First one in the Ready List Time Complexity O(1)

Selection sort for each changeTime Complexity O(N)

Task Scheduler (cont)TASK 1

NEXTPREV

Priority

TASK 2

NEXTPREV

Priority

TASK 3

NEXTPREV

Priority

TASK 4

NEXTPREV

Priority0

0OSTCBList

Method 2Get the highest priority

Modify priority state

Use a Ready Table a Priority TCB Table and one variable to selectTime Complexity O(1)

Maintain a Ready Table a Priority TCB Tabke and one variableTime Complexity O(1)

Task Scheduler (cont)

TASK 1

NEXTPREV

Priority

TASK 2

NEXTPREV

Priority

TASK 3

NEXTPREV

Priority

TASK 4

NEXTPREV

Priority0

0OSTCBList

Task Scheduler (cont)Get the highest priority

0 0 0 0 0 1 0 00 0 0 0 0 0 0 00 0 1 1 0 1 0 00 0 0 0 0 0 0 00 1 0 0 0 0 1 01 0 0 0 0 0 1 10 0 0 0 0 0 0 01 0 0 0 0 0 0 0

1OSRdyGrp

0101101

TASK 1

NEXTPREV

Priority

TASK 2

NEXTPREV

Priority

TASK 3

NEXTPREV

Priority

TASK 4

NEXTPREV

Priority0

0OSTCBList

Task Scheduler (cont)Modify priority stateOSRdyGrp |= OSMapTbl[prio gtgt 3]OSRdyTbl[prio gtgt 3] |= OSMapTbl[prio amp 0x07]

Task Scheduler (cont)0 0 0 0 0 1 0 00 0 0 0 0 0 0 00 0 1 1 0 1 0 00 0 0 0 0 0 0 00 1 0 0 0 0 1 01 0 0 0 0 0 1 10 0 0 0 0 0 0 01 0 0 0 0 0 0 0

1 0 1 1 0 1 0 1

0 0 0 1 1 1 1 1

OSRdyGrp

Task Priority = 31

3

1

7

1

31

OSSched(void)void OSSched (void) INT8U y OS_ENTER_CRITICAL() if ((OSLockNesting | OSIntNesting) == 0) y = OSUnMapTbl[OSRdyGrp] OSPrioHighRdy = (INT8U)((y ltlt 3) + OSUnMapTbl[OSRdyTbl[y]]) if (OSPrioHighRdy = OSPrioCur) OSTCBHighRdy = OSTCBPrioTbl[OSPrioHighRdy] OSCtxSwCtr++ OS_TASK_SW() OS_EXIT_CRITICAL()

Task Pending Task pending occur when interrupt

raise When waiting some event message

or semaphore When one task delays itself When one task is preempted by

higher priority task

OSMBoxPend()OSQPend()OSSemPend()

OSTaskSuspend()OSTimeDly()OSTimeDlyHMSM()

Task Creation OSTaskCreate() OSTaskCreateExt() Create task before OSStart() or in Running state But not permit to create task in ISR

OSTaskCreate() Check priority

number

Check OSTCBPrioTbl OSTaskStkInit()

OSTCBInit() OSTaskCtr++ OSSched()

if (OSRunning)

OSStackCheck

OSTaskCreateExt() Check priority

number

Check OSTCBPrioTbl OSTaskStkInit()

OSTCBInit() OSTaskCtr++ OSSched()

if (OSRunning)

Task Deletion

TASK 1

NEXTPREV

Priority

TASK 2

NEXTPREV

Priority

TASK 3

NEXTPREV

Priority

TASK 4

NEXTPREV

Priority0

0OSTCBList

Interrupts Interrupt Service RoutineStep1save CPU registersStep2call OSIntEnter () or OSIntNesting add one directlyStep3execution the service codeStep4call OSIntExit() Step5restore CPU registersStep6call interrupt return instruction

Context switch

Clock ticks 10-100Hz void OSTickISR(void) OSTimeTick() OSTimeTick() execution time is in proportion to number of Task TASK 1

NEXTPREV OSTCBDly

TASK 2NEXTPREV OSTCBDly

TASK 3NEXTPREV OSTCBDly

TASK 4NEXTPREV OSTCBDly 0

0OSTCBList

OSTimeTick() if (ptcb-gtOSTCBDly = 0) if (--ptcb-gtOSTCBDly == 0) if ((ptcb-gtOSTCBStat amp OS_STAT_SUSPEND)) OSRdyGrp |= ptcb-gtOSTCBBitY OSRdyTbl[ptcb-gtOSTCBY] |= ptcb-gtOSTCBBitX else ptcb-gtOSTCBDly = 1

Time Management Using clock tick to implement time delays and timeouts OSTimeDly() OSTimeDlyHMSM() OSTimeDlyResume() OSTimeGet() OSTimeSet() Defined in OS_TimeC

OSTimeDly()void OSTimeDly (INT16U ticks) if (ticks gt 0)

OS_ENTER_CRITICAL() if ((OSRdyTbl[OSTCBCur-gtOSTCBY] amp= ~OSTCBCur-gtOSTCBBitX) == 0) OSRdyGrp amp= ~OSTCBCur-gtOSTCBBitY OSTCBCur-gtOSTCBDly = ticks

OS_EXIT_CRITICAL() OSSched()

uCOSII initialization OSIint() initialize all variables and data structure for system Defined in OS_COREC

OSPrioCur = 0OSPrioHighRdy = 0OSTCBCur = NULLOSTCBHighRdy = OLOSTime = 0OSIntNesting = 0OSLockNesting = 0 OSCtxSwCtr = 0OSTaskCtr = 2OSRunning = FALSEOSCPUUsage = 0OSIdleCtrMax = 0L OSIdleCtrRun = 0LOSIdleCtr = 0LOSStatRdy = FALSE

Free TCB List

Free Event List

Free Queue List

Free Memory List

Create a TaskPriority = 6

OSPrioCur = 6OSPrioHighRdy = 6OSTCBCur OSTCBHighRdy OSTime = 0OSIntNesting = 0OSLockNesting = 0 OSCtxSwCtr = 0OSTaskCtr = 3OSRunning = TRUEOSCPUUsage = 0OSIdleCtrMax = 0L OSIdleCtrRun = 0LOSIdleCtr = 0LOSStatRdy = FALSE

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Waiting List