SCM polling program framework based on linked list management

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source ：ERYUESANHI

Hello everyone , This is Xiao Yao , Today, I share the article of bare metal program framework of single chip microcomputer .

1

The importance of the overall program architecture

Many people, especially beginners, often want to write a little bit when they write code , In the beginning, there was no overall plan , This leads to more and more messy code ,bug constantly .

In the end, the code seems to run smoothly ( Maybe and really no problem ), But it will waste a lot of time to add a function , And even cause the whole code to crash .

therefore , At the beginning of a project, it is necessary to spend more time on the architecture design of the code . After the code structure is determined, you will find that the time to knock code will be very fast , And in the later debugging, it will not look for problems like headless flies . Of course , Debugging is also a technology .

In the process of learning real-time operating system , It is found that the coupling between real-time operating system framework and individual business code is very low , All you need to do is register the business code with a certain interface function and then give it to the operating system for hosting , It is very convenient .

But the scheduling of the operating system is too complex , Here we use the thinking mode of the operating system to reconstruct the time slice polling framework . Complete decoupling of the framework is realized , Users only need to include header files , And in the process of using, there is no need to change the library file that has been written .

2

Reference code

Let's start with demo, The demo Is to use the computer to open two threads ： A thread simulates the timer interrupt of single chip microcomputer to generate time slice and poll a clock , The other thread simulates the time slice polling scheduler that has been running in the main function .

1#include <thread>
  2#include <stdio.h>
  3#include <windows.h>
  4#include "timeslice.h"
  5
  6//  establish 5 A task object 
  7TimesilceTaskObj task_1, task_2, task_3, task_4, task_5;
  8
  9//  Specific task functions 
 10void task1_hdl()
 11{
 12    printf(">> task 1 is running ...\n");
 13}
 14
 15void task2_hdl()
 16{
 17    printf(">> task 2 is running ...\n");
 18}
 19
 20void task3_hdl()
 21{
 22    printf(">> task 3 is running ...\n");
 23}
 24
 25void task4_hdl()
 26{
 27    printf(">> task 4 is running ...\n");
 28}
 29
 30void task5_hdl()
 31{
 32    printf(">> task 5 is running ...\n");
 33}
 34
 35//  Initialize the task object , And add the task to the time slice polling schedule 
 36void task_init()
 37{
 38    timeslice_task_init(&task_1, task1_hdl, 1, 10);
 39    timeslice_task_init(&task_2, task2_hdl, 2, 20);
 40    timeslice_task_init(&task_3, task3_hdl, 3, 30);
 41    timeslice_task_init(&task_4, task4_hdl, 4, 40);
 42    timeslice_task_init(&task_5, task5_hdl, 5, 50);
 43    timeslice_task_add(&task_1);
 44    timeslice_task_add(&task_2);
 45    timeslice_task_add(&task_3);
 46    timeslice_task_add(&task_4);
 47    timeslice_task_add(&task_5);
 48}
 49
 50
 51//  Open two threads to simulate the running process on MCU 
 52void timeslice_exec_thread()
 53{
 54    while (true)
 55    {
 56        timeslice_exec();
 57    }
 58}
 59
 60void timeslice_tick_thread()
 61{
 62    while (true)
 63    {
 64        timeslice_tick();
 65        Sleep(10);
 66    }
 67}
 68
 69int main()
 70{
 71    task_init();
 72
 73    printf(">> task num: %d\n", timeslice_get_task_num());
 74    printf(">> task len: %d\n", timeslice_get_task_timeslice_len(&task_3));
 75
 76    timeslice_task_del(&task_2);
 77    printf(">> delet task 2\n");
 78    printf(">> task 2 is exist: %d\n", timeslice_task_isexist(&task_2));
 79
 80    printf(">> task num: %d\n", timeslice_get_task_num());
 81
 82    timeslice_task_del(&task_5);
 83    printf(">> delet task 5\n");
 84
 85    printf(">> task num: %d\n", timeslice_get_task_num());
 86
 87    printf(">> task 3 is exist: %d\n", timeslice_task_isexist(&task_3));
 88    timeslice_task_add(&task_2);
 89    printf(">> add task 2\n");
 90    printf(">> task 2 is exist: %d\n", timeslice_task_isexist(&task_2));
 91
 92    timeslice_task_add(&task_5);
 93    printf(">> add task 5\n");
 94
 95    printf(">> task num: %d\n", timeslice_get_task_num());
 96
 97    printf("\n\n========timeslice running===========\n");
 98
 99    std::thread thread_1(timeslice_exec_thread);
100    std::thread thread_2(timeslice_tick_thread);
101
102    thread_1.join();
103    thread_2.join();
104
105
106    return 0;
107}

The operation results are as follows ：

It can be seen from the above examples that , This framework is very easy to use , You may not even know how it works , With just a few simple interfaces, you can quickly create tasks and add them to the time slice polling framework , It's very easy to use .

3

Time slice polling Architecture

In fact, this part mainly uses object-oriented thinking , Using structures as objects , And use the structure pointer as a parameter to pass , This saves resources , And it's very efficient .

The most difficult part is the use of intrusive linked lists , This kind of linked list is widely used in some operating system kernels , Here is Reference resources RT-Thread Implementation of intrusive linked list in real-time operating system .

h file ：

1#ifndef _TIMESLICE_H
 2#define _TIMESLICE_H
 3
 4#include "./list.h"
 5
 6typedef enum {
 7    TASK_STOP,
 8    TASK_RUN
 9} IsTaskRun;
10
11typedef struct timesilce
12{
13    unsigned int id;
14    void (*task_hdl)(void);
15    IsTaskRun is_run;
16    unsigned int timer;
17    unsigned int timeslice_len;
18    ListObj timeslice_task_list;
19} TimesilceTaskObj;
20
21void timeslice_exec(void);
22void timeslice_tick(void);
23void timeslice_task_init(TimesilceTaskObj* obj, void (*task_hdl)(void), unsigned int id, unsigned int timeslice_len);
24void timeslice_task_add(TimesilceTaskObj* obj);
25void timeslice_task_del(TimesilceTaskObj* obj);
26unsigned int timeslice_get_task_timeslice_len(TimesilceTaskObj* obj);
27unsigned int timeslice_get_task_num(void);
28unsigned char timeslice_task_isexist(TimesilceTaskObj* obj);
29
30#endif

.c file ：

1#include "./timeslice.h"
 2
 3static LIST_HEAD(timeslice_task_list);
 4
 5void timeslice_exec()
 6{
 7    ListObj* node;
 8    TimesilceTaskObj* task;
 9
10    list_for_each(node, &timeslice_task_list)
11    {
12
13        task = list_entry(node, TimesilceTaskObj, timeslice_task_list);
14        if (task->is_run == TASK_RUN)
15        {
16            task->task_hdl();
17            task->is_run = TASK_STOP;
18        }
19    }
20}
21
22void timeslice_tick()
23{
24    ListObj* node;
25    TimesilceTaskObj* task;
26
27    list_for_each(node, &timeslice_task_list)
28    {
29        task = list_entry(node, TimesilceTaskObj, timeslice_task_list);
30        if (task->timer != 0)
31        {
32            task->timer--;
33            if (task->timer == 0)
34            {
35                task->is_run = TASK_RUN;
36                task->timer = task->timeslice_len;
37            }
38        }
39    }
40}
41
42unsigned int timeslice_get_task_num()
43{
44    return list_len(&timeslice_task_list);
45}
46
47void timeslice_task_init(TimesilceTaskObj* obj, void (*task_hdl)(void), unsigned int id, unsigned int timeslice_len)
48{
49    obj->id = id;
50    obj->is_run = TASK_STOP;
51    obj->task_hdl = task_hdl;
52    obj->timer = timeslice_len;
53    obj->timeslice_len = timeslice_len;
54}
55
56void timeslice_task_add(TimesilceTaskObj* obj)
57{
58    list_insert_before(&timeslice_task_list, &obj->timeslice_task_list);
59}
60
61void timeslice_task_del(TimesilceTaskObj* obj)
62{
63    if (timeslice_task_isexist(obj))
64        list_remove(&obj->timeslice_task_list);
65    else
66        return;
67}
68
69
70unsigned char timeslice_task_isexist(TimesilceTaskObj* obj)
71{
72    unsigned char isexist = 0;
73    ListObj* node;
74    TimesilceTaskObj* task;
75
76    list_for_each(node, &timeslice_task_list)
77    {
78        task = list_entry(node, TimesilceTaskObj, timeslice_task_list);
79        if (obj->id == task->id)
80            isexist = 1;
81    }
82
83    return isexist;
84}
85
86unsigned int timeslice_get_task_timeslice_len(TimesilceTaskObj* obj)
87{
88    return obj->timeslice_len;
89}

4

Bottom intrusive two-way linked list

The linked list is linux It's widely used in the kernel , It's also very classic , Its principle can refer to the article ：

https://www.cnblogs.com/skywang12345/p/3562146.html

.h file ：

1#ifndef _LIST_H
 2#define _LIST_H
 3
 4#define offset_of(type, member)             (unsigned long) &((type*)0)->member
 5#define container_of(ptr, type, member)     ((type *)((char *)(ptr) - offset_of(type, member)))
 6
 7typedef struct list_structure
 8{
 9    struct list_structure* next;
10    struct list_structure* prev;
11} ListObj;
12
13#define LIST_HEAD_INIT(name)    {&(name), &(name)}
14#define LIST_HEAD(name)         ListObj name = LIST_HEAD_INIT(name)
15
16void list_init(ListObj* list);
17void list_insert_after(ListObj* list, ListObj* node);
18void list_insert_before(ListObj* list, ListObj* node);
19void list_remove(ListObj* node);
20int list_isempty(const ListObj* list);
21unsigned int list_len(const ListObj* list);
22
23#define list_entry(node, type, member) \
24    container_of(node, type, member)
25
26#define list_for_each(pos, head) \
27    for (pos = (head)->next; pos != (head); pos = pos->next)
28
29#define list_for_each_safe(pos, n, head) \
30  for (pos = (head)->next, n = pos->next; pos != (head); \
31    pos = n, n = pos->next)
32
33#endif

.c file ：

1#include "list.h"
 2
 3void list_init(ListObj* list)
 4{
 5    list->next = list->prev = list;
 6}
 7
 8void list_insert_after(ListObj* list, ListObj* node)
 9{
10    list->next->prev = node;
11    node->next = list->next;
12
13    list->next = node;
14    node->prev = list;
15}
16
17void list_insert_before(ListObj* list, ListObj* node)
18{
19    list->prev->next = node;
20    node->prev = list->prev;
21
22    list->prev = node;
23    node->next = list;
24}
25
26void list_remove(ListObj* node)
27{
28    node->next->prev = node->prev;
29    node->prev->next = node->next;
30
31    node->next = node->prev = node;
32}
33
34int list_isempty(const ListObj* list)
35{
36    return list->next == list;
37}
38
39unsigned int list_len(const ListObj* list)
40{
41    unsigned int len = 0;
42    const ListObj* p = list;
43    while (p->next != list)
44    {
45        p = p->next;
46        len++;
47    }
48
49    return len;
50}

Here we are , A brand new , Completely decoupled , Very convenient and easy to use time slice polling framework to complete .

Copyright notice ： Source network of this paper , Free delivery of knowledge , The copyright belongs to the original author . If involves the work copyright question , Please contact me to delete .

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