调用相同函数时的线程问题 [英] Threading issue when calling same function

问题描述

我正在尝试创建给定函数的 4 个实例，但无法确定被调用的函数如何知道哪个线程调用了它.

I am trying to create 4 instances of a given function but having trouble working out how the function called knows which thread has called it.

这是在我的头文件中:

// GPIO PINS stored within structs, for each sonic range finder.
typedef struct sonicPins {
    // front left pins.
    int trig1;
    int echo1;
    // front right pins.
    int trig2;
    int echo2;
    // rear left pins.
    int trig3;
    int echo3;
    // rear right pins.
    int trig4;
    int echo4;
} args;

void* setup(void *pinsPtr);
extern int threadFunc();

这是在我的 C 文件中.

This is within my C file.

int threadFunc()
{
    struct sonicPins * pins;
    pthread_create(&pt1, NULL, setup, (void*) pins);
    pthread_create(&pt2, NULL, setup, (void*) pins);
    pthread_create(&pt3, NULL, setup, (void*) pins);
    pthread_create(&pt4, NULL, setup, (void*) pins);
    return 1;
}

以下代码片段的职责是设置引脚值并运行操作来管理传感器.每个传感器都有自己的回声和触发值，它们是整数.

The duty of the snippet below is to set pin value and run operations to manage a sensor. Each sensor is has its own echo and trigger values which are integers.

void* setup(void *pinsPtr)
{
    struct sonicPins *ptr = pinsPtr;
    int trig = 0, Echo = 0;

    printf("thread id %d\n", pt1);
    if (pt1 == 1993737328) {
        trig = ptr->trig1;
        Echo = ptr->echo1;
    } else if (pt2 == 1986323568) {
        trig = ptr->trig2;
        Echo = ptr->trig2;
    } else if (pt3 == 1977164912) {
        trig = ptr->trig3;
        Echo = ptr->trig3;
    } else if (pt4 == 4) {
        trig = ptr->trig4;
        Echo = ptr->echo4;
    }
    …other work…
}

我是 C 的新手，确实忘记了一个线程 ID 并不总是相同的，但我不确定我可以使用什么来进行处理.你能提出一些建议吗?

I am new to C and did forget a thread ID isn't always the same, but I'm not sure what I can use to base the handling on. Can you suggest something?

推荐答案

您需要的是一个结构体数组，其中每个结构体都有一个 echo 和 trigger 值.然后将不同的数组条目传递给每个线程，这样每个线程只知道自己的 echo 和 trigger 值.

What you need is an array of structs, where each struct has one echo and trigger value. Then you pass a different array entry to each thread, so that each thread only knows its own echo and trigger values.

#include <stdio.h>
#include <pthread.h>

typedef struct sonicPins {
    int trig;
    int echo;
} sonicPins;

void *threadFunc( void *args )
{
    sonicPins *pins = args;
    printf( "trig=%d echo=%d\n", pins->trig, pins->echo );
    return NULL;
}

int main( void )
{
    pthread_t threadID[4];
    sonicPins pinsArray[4] = { { 1, 2 }, { 4, 8 }, { 16, 32 }, { 64, 128 } };

    for ( int i = 0; i < 4; i++ )
    {
        if ( pthread_create( &threadID[i], NULL, threadFunc, &pinsArray[i] ) != 0 )
            fprintf( stderr, "pthread_create failed: %d\n", i );
    }

    for ( int i = 0; i < 4; i++ )
        pthread_join( threadID[i], NULL );
}

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