Question

我发送sturct dataBlock到我的主题，其中包含a pointer到同一个listRoot（适用于所有主题），int indexInForLoop和int listSize;列表中的节点有一个int值，要处理的灰烬和一个int工作者，它是nrOfListElements％nrOfWorkers（Threads）。但不知怎的，我发送到每个线程的结构是相同的，但它不应该每个都应该有一个不同的int变量与indexFromForLoop。我做错了什么？

终端输出：

node #1 worker: 1  value: 86
node #2 worker: 0  value: 77
node #3 worker: 1  value: 15
node #4 worker: 0  value: 93
node #5 worker: 1  value: 35
? List got populated
workersInput: 2
in for, ret= 0
in for, ret= 0
* Thread start:             id: 3067579200^
forID_ 1 
->val: 86   
valid for sqrt 
* Thread start:             id: 3075971904^
forID_ 1 
->val: 86   
valid for sqrt

代码：

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#include <math.h>   

#define workTime 5
#define workersLimitNr 3

struct dataBlock{
    struct node *root;
    int listSize;
    int forIndex;
};

struct node { // std linked list node
    int value;
    int worker;
    struct node *next;
};

int slots = 0; // only 3 threads are allowed to access the list
int availableCheck(){   // check if thread can acces the list
    if(slots < 3) return 0;
    else return -1;
}

pthread_mutex_t mutp = PTHREAD_MUTEX_INITIALIZER;   //condvar mutex
pthread_cond_t  condvar = PTHREAD_COND_INITIALIZER;   //condvar

void * worker( void *data ){
    struct dataBlock *inData = (struct dataBlock *) data;
    struct node *root = inData->root;
    int listSize =  inData->listSize;
    int forIndex = inData ->forIndex;

    printf( "* Thread start:            ^\n"); 

    pthread_mutex_lock( &mutp );
    if(availableCheck() < 0){
        printf( " ^^^ List not available yet... \n" ); 
        pthread_cond_wait( &condvar, &mutp );
    } 
    struct node *it = root;
    printf("forID_ %d \n", forIndex);
    while(it->next != NULL){
        if(forIndex == it->worker){
            printf("valid for sqrt \n");
            if(it->value > 2){
                sqrt(it->value);
                break;
            }
        }
        it = it->next;
        printf("->val: %d   \n", it->value);
    }

    pthread_cond_signal( &condvar ); // 
    pthread_mutex_unlock( &mutp ); 
    return NULL;
}

int main( int argc, char *argv[] ){
    if ( argc != 3 ){
        printf( "Programm must be called with \n NR of elements and NR of workers! \n " );
        exit( 1 );
    }

    int i;
    struct node *root;
    struct node *iterator;  

//prepare list for task
    int listSize = atoi(argv[1]);
    int nrWorkers = atoi(argv[2]);
    root = malloc(sizeof( struct node) );

    root->value = rand() % 100;
    root->worker = 0;
    iterator = root;

    for( i=1; i<listSize; i++ ){
        iterator->next = malloc(sizeof(struct node));
        iterator = iterator->next;
        iterator->value = rand() % 100;
        iterator->worker = i % nrWorkers;
        printf("node #%d worker: %d  value: %d\n", i, iterator->worker,iterator->value);
    }
    printf("? List got populated\n");

// Create all threads to parse the link list
    int ret;    
    printf("workersInput: %d\n",nrWorkers);

    pthread_t w_thread;
    pthread_t* w_threads = malloc(nrWorkers * sizeof(w_thread));

    struct dataBlock *data = malloc(sizeof(struct dataBlock));
    data->root = root;
    data->listSize = listSize;

    for( i=0; i < nrWorkers; i++ ){ 
        data->forIndex = i;
        ret = pthread_create ( &w_threads[i], NULL, worker, (void *) data );
        if( ret ) {
            perror("Thread creation fail");
            exit(2);    
        }   
        printf("in for, ret= %d\n",ret);
    } 

    for ( i = 0; i < nrWorkers; i++){
        pthread_join(w_threads[i],NULL);
    }

    free(root);
    free(iterator);
    return 0;
}

编辑：我使用了pthread_self（），我确认存在不同的威胁

Answer 1

使用

data->forIndex = i;

你覆盖以前的值。因为你只有一个dataBlock，每个线程都会看到同一个地方。因为创建一个线程不意味着“在执行循环中的下一个语句之前启动它”，所以每个线程看到的值都是纯粹的运气。

您必须为每个帖子分配一个dataBlock，并将每个dataBLock仅提供给一个帖子。

pThread函数参数，向每个线程发送相同的值，等待其他东西

1 个答案: