一、介紹

調(diào)度器是常用的一種編程框架，也是操作系統(tǒng)的拆分多任務(wù)的核心，比如單片機(jī)的裸機(jī)程序框架，網(wǎng)絡(luò)協(xié)議棧的框架如can網(wǎng)關(guān)、485網(wǎng)關(guān)等等，使用場(chǎng)合比較多，是做穩(wěn)定產(chǎn)品比較常用的編程技術(shù)

二、原理

1、超級(jí)循環(huán)

?

void?main()
{
?while(1)
?{
??task1();
??task2();
??...
?}
}
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2、時(shí)間片與時(shí)標(biāo)

1）我們把cpu執(zhí)行時(shí)間分成一段一段的，每一段時(shí)間稱為時(shí)間片2）時(shí)間片的時(shí)間計(jì)時(shí)由定時(shí)器完成，把定時(shí)器定的時(shí)間成為時(shí)標(biāo)

3、調(diào)度算法介紹

1）時(shí)間片輪轉(zhuǎn)調(diào)度2）強(qiáng)占試調(diào)度

4、注意事項(xiàng)

1）所有任務(wù)的執(zhí)行時(shí)間不能超過時(shí)標(biāo)的時(shí)間2）任務(wù)中不能有任何阻塞，比如使用延時(shí)函數(shù)3）任務(wù)中的延時(shí)或者長(zhǎng)時(shí)間任務(wù)利用狀態(tài)機(jī)拆分成多段

三、任務(wù)調(diào)度代碼實(shí)現(xiàn)

這里拿linux來測(cè)試schduler.c

?

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//????????頭文件區(qū)
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#include?
#include?"scheduler.h"

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//????????接口定義區(qū)
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
#define?MAX_TASKS?10
static?volatile?unsigned?char?cur_task_num?=?0;

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//????????變量定義區(qū)
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
static?running_queue_def?running_queue[MAX_TASKS]?=?{0};

//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
//????????函數(shù)定義區(qū)
//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
int?create_task(const?void?(*fun)(),?unsigned?short?period)
{
????unsigned?char?i;

?if(cur_task_num?>=?MAX_TASKS)
?{
??printf("over?limit?max_tasks
");
??return?-1;
?}
????running_queue[i].fun?=?fun;
????running_queue[i].period?=?period;
????running_queue[i].cnt?=?0;
????
????cur_task_num++;
????return?0;
}

int?scheduler_run()
{
????unsigned?char?i;
????for(i?=?0;?i??0)
????????{
????????????running_queue[i].cnt--;
????????}
????????else
????????{
????????????running_queue[i].cnt?=?running_queue[i].period;
????????????running_queue[i].fun();
????????}
????}

????return?0;
}

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schduler.h

?

#ifndef?__SCHEDULER_H
#define?__SCHEDULER_H

typedef?struct?{
?????void?(*fun)();????????//運(yùn)行函數(shù)
?????unsigned?short?period;//周期
????????unsigned?short?cnt;
}running_queue_def;

int?create_task(const?void?(*fun)(),?unsigned?short?period);
int?scheduler_run();

#endif

?

main.c

?

#include?"scheduler.h"
#include?
#include?

void?task1()
{
????printf("task1?run
");
}

void?task2()
{
????printf("task2?run
");
}

int?main()
{
????create_task(task1,?1000);
????create_task(task2,?2000);
????while(1)
????{
????????scheduler_run();
????????usleep(1000);
????}

????return?0;
}

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編譯腳本

build.sh

?

echo?"delet?main"
rm?-rf?main
sleep?1

gcc?main.c?scheduler.c?-o?main??-w

echo?"build?ok?"
./main

?

　　審核編輯：湯梓紅