多线程传参

  多线程传参，分为两种方式。一种是设置 ==全局变量==；另一种是通过int pthread_create（（pthread_t *thread, pthread_attr_t *attr, void *（*start_routine）（void *）, void *arg）函数的最后一项参数传参，通过pthread_create 参数传参要注意，其参数类型为（void *）。

设置全局变量时，应该注意加上同步机制，例如如p v操作或者锁机制。避免多线程访问同一资源时发生竞争。如果线程个数可以确定，线程间是同步进行的，则线程间的私有资源(线程间使用的buffer，变量）不需要加锁，这种情况一般是设置全局标志来使线程同步。

函数传参时，避免主程序因为等待线程而阻塞，使用pthread_detach(pid)函数使线程函数自运行。则该线程运行结束后会自动释放所有资源。使用函数传参时，注意以下几个易错点：
 1. 传递的参数类型是个（void型）指针。
 2. 参数传递中，不能使用局部变量int a， 以&a 的方式传参。可采用

int a = 5;//局部变量pthread_create（pid,  NULL,  thread_func,  (void  *)a）;........void *thread_func(void *argc){    ......       b = (int )argc;//实现局部变量的对线程函数的传参    ......}

函数传参例子

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <pthread.h>#include <sys/types.h>          /* See NOTES */#include <sys/socket.h>#include <unistd.h>#include <netinet/in.h>#include <arpa/inet.h>#include <netdb.h>#include <unistd.h>void *thread1_func(void *argc){    int ret;    int iSocket =(int )argc;    char heartSendBuf[14] = {'\0'};    while(1) {        ret = send(iSocket, heartSendBuf, 14, 0);        if (ret < 0){            perror("thread1_func:");            close(iSocket);            pthread_exit(NULL);         }        printf("the heart send to client ok!\n");    }}void *thread2_func(void *argc){    int ret;    int iSocket =(int )argc;    char heartRecvBuf[14] = {'1'};    sleep(4);    while(1) {        ret = recv(iSocket, heartRecvBuf, 14, 0);        if (ret < 0){            perror("thread2_func:");//          close(iSocket);            pthread_exit(NULL);         }        printf("the heart recv from client ok!\n");    }}#define SERVER_IP "127.0.0.1"static unsigned short tmp_port = 8803;int start_server(void){    int iSocket;    int nZero = 0;    struct timeval t = {20, 0};    struct sockaddr_in myserver_addr;    struct sockaddr_in client_addr;    socklen_t addrlen = sizeof(myserver_addr);    memset(&myserver_addr, 0, sizeof(myserver_addr));    myserver_addr.sin_family = AF_INET;    myserver_addr.sin_port = htons(tmp_port);    myserver_addr.sin_addr.s_addr = inet_addr("192.168.0.18");    memset(&client_addr, 0, sizeof(client_addr));    client_addr.sin_family = AF_INET;    client_addr.sin_port = htons(8802);    client_addr.sin_addr.s_addr = inet_addr("192.168.0.20");    if ((iSocket = socket(AF_INET, SOCK_DGRAM, 0)) < 0 ){        perror("Create Socket failed: ");        exit(1);    }    if (bind(iSocket, (struct sockaddr *)&myserver_addr, sizeof(myserver_addr))== -1){        perror("bind error");    }else {        printf("bind ok\n");    }    if (connect(iSocket, (struct sockaddr *)&client_addr, addrlen) != 0){        perror("connect error");        return -1;    }else {        printf("connect ok\n");    }    if (setsockopt(iSocket, SOL_SOCKET, SO_SNDBUF, (char *)&nZero, sizeof(nZero)) < 0){        perror("thread_send:setsockopt heartSendBuf error");        return -1;    }    if (setsockopt(iSocket, SOL_SOCKET, SO_RCVTIMEO, &t, sizeof(t)) < 0){        perror("thread_recv:setsockopt error");        return -1;     }     return iSocket;}int main(int argc, char **argv){    int ret;    int iSocket;    pthread_t pid1,pid2;    //create client    iSocket = start_server();    if (iSocket < 0){        perror("create client server error");        return -1;    }    ret = pthread_create(&pid1, NULL, thread1_func, (void *)iSocket);    if (ret < 0){        perror("create thread_caller error");        return -1;    }else {        printf(" create heart send thread ok\n");    }    pthread_detach(pid1);    ret = pthread_create(&pid2, NULL, thread2_func, (void *)iSocket);    if (ret < 0){        perror("create thread_caller error");        return -1;    }else {        printf(" create heart send thread ok\n");    }    pthread_detach(pid2);    while(1);}

总结

    多线程传参，传参的值是（void *）类型，属于地址传参。在传入多个值时应当使用结构体封装。当使局部变量时，注意提前释放局部变量资源，生命周期应该等待线程结束。