#include <iostream>
#include <cstdlib>
#include <pthread.h>
using namespace std;
#define NUM_THREADS     5
struct thread_data{
   int  thread_id;
   char *message;
};
void *PrintHello(void *threadarg)
{
   struct thread_data *my_data;
   my_data = (struct thread_data *) threadarg;
   cout << "Thread ID : " << my_data->thread_id ;
   cout << " Message : " << my_data->message << endl;
   pthread_exit(NULL);
}
int main ()
{
   pthread_t threads[NUM_THREADS];
   struct thread_data td[NUM_THREADS];
   int rc;
   int i;
   for( i=0; i < NUM_THREADS; i++ ){
      cout <<"main() : creating thread, " << i << endl;
      td[i].thread_id = i;
      td[i].message = "This is message";
      rc = pthread_create(&threads[i], NULL,
                          PrintHello, (void *)&td[i]); //传入到参数必须强转为void*类型，即无类型指针
      if (rc){
         cout << "Error:unable to create thread," << rc << endl;
         exit(-1);
      }
   }
   pthread_exit(NULL);
}

#include <iostream>
#include <pthread.h>
using namespace std;
#define NUM_THREADS 5
int sum = 0; //定义全局变量，让所有线程同时写，这样就需要锁机制
pthread_mutex_t sum_mutex; //互斥锁
void* say_hello( void* args )
{
    cout << "hello in thread " << *(( int * )args) << endl;
    pthread_mutex_lock( &sum_mutex ); //先加锁，再修改sum的值，锁被占用就阻塞，直到拿到锁再修改sum;
    cout << "before sum is " << sum << " in thread " << *( ( int* )args ) << endl;
    sum += *( ( int* )args );
    cout << "after sum is " << sum << " in thread " << *( ( int* )args ) << endl;
    pthread_mutex_unlock( &sum_mutex ); //释放锁，供其他线程使用
    pthread_exit( 0 );
}
int main()
{
    pthread_t tids[NUM_THREADS];
    int indexes[NUM_THREADS];
    pthread_attr_t attr; //线程属性结构体，创建线程时加入的参数
    pthread_attr_init( &attr ); //初始化
    pthread_attr_setdetachstate( &attr, PTHREAD_CREATE_JOINABLE ); //是设置你想要指定线程属性参数，这个参数表明这个线程是可以join连接的，join功能表示主程序可以等线程结束后再去做某事，实现了主程序和线程同步功能
    pthread_mutex_init( &sum_mutex, NULL ); //对锁进行初始化
    for( int i = 0; i < NUM_THREADS; ++i )
    {
        indexes[i] = i;
        int ret = pthread_create( &tids[i], &attr, say_hello, ( void* )&( indexes[i] ) ); //5个进程同时去修改sum
        if( ret != 0 )
        {
            cout << "pthread_create error:error_code=" << ret << endl;
        }
    }
    pthread_attr_destroy( &attr ); //释放内存
    void *status;
    for( int i = 0; i < NUM_THREADS; ++i )
    {
        int ret = pthread_join( tids[i], &status ); //主程序join每个线程后取得每个线程的退出信息status
        if( ret != 0 )
        {
            cout << "pthread_join error:error_code=" << ret << endl;
        }
    }
    cout << "finally sum is " << sum << endl;
    pthread_mutex_destroy( &sum_mutex ); //注销锁
}

hello in thread hello in thread 1hello in thread 3
0
hello in thread 2
before sum is 0 in thread 1
hello in thread 4
after sum is 1 in thread 1
before sum is 1 in thread 3
after sum is 4 in thread 3
before sum is 4 in thread 4
after sum is 8 in thread 4
before sum is 8 in thread 0
after sum is 8 in thread 0
before sum is 8 in thread 2
after sum is 10 in thread 2
finally sum is 10

#include <iostream>
#include <pthread.h>
#include <stdio.h>
using namespace std;
#define BOUNDARY 5
int tasks = 10;
pthread_mutex_t tasks_mutex; //互斥锁
pthread_cond_t tasks_cond; //条件信号变量，处理两个线程间的条件关系，当task>5，hello2处理，反之hello1处理，直到task减为0
void* say_hello2( void* args )
{
    pthread_t pid = pthread_self(); //获取当前线程id
    cout << "[" << pid << "] hello in thread " <<  *( ( int* )args ) << endl;
    bool is_signaled = false; //sign
    while(1)
    {
        pthread_mutex_lock( &tasks_mutex ); //加锁
        if( tasks > BOUNDARY )
        {
            cout << "[" << pid << "] take task: " << tasks << " in thread " << *( (int*)args ) << endl;
            --tasks; //modify
        }
        else if( !is_signaled )
        {
            cout << "[" << pid << "] pthread_cond_signal in thread " << *( ( int* )args ) << endl;
            pthread_cond_signal( &tasks_cond ); //signal:向hello1发送信号，表明已经>5
            is_signaled = true; //表明信号已发送，退出此线程
        }
        pthread_mutex_unlock( &tasks_mutex ); //解锁
        if( tasks == 0 )
            break;
    }
}
void* say_hello1( void* args )
{
    pthread_t pid = pthread_self(); //获取当前线程id
    cout << "[" << pid << "] hello in thread " <<  *( ( int* )args ) << endl;
    while(1)
    {
        pthread_mutex_lock( &tasks_mutex ); //加锁
        if( tasks > BOUNDARY )
        {
            cout << "[" << pid << "] pthread_cond_signal in thread " << *( ( int* )args ) << endl;
            pthread_cond_wait( &tasks_cond, &tasks_mutex ); //wait:等待信号量生效，接收到信号，向hello2发出信号，跳出wait,执行后续
        }
        else
        {
            cout << "[" << pid << "] take task: " << tasks << " in thread " << *( (int*)args ) << endl;
            --tasks;
        }
        pthread_mutex_unlock( &tasks_mutex ); //解锁
        if( tasks == 0 )
            break;
    }
}
int main()
{
    pthread_attr_t attr; //线程属性结构体，创建线程时加入的参数
    pthread_attr_init( &attr ); //初始化
    pthread_attr_setdetachstate( &attr, PTHREAD_CREATE_JOINABLE ); //是设置你想要指定线程属性参数，这个参数表明这个线程是可以join连接的，join功能表示主程序可以等线程结束后再去做某事，实现了主程序和线程同步功能
    pthread_cond_init( &tasks_cond, NULL ); //初始化条件信号量
    pthread_mutex_init( &tasks_mutex, NULL ); //初始化互斥量
    pthread_t tid1, tid2; //保存两个线程id
    int index1 = 1;
    int ret = pthread_create( &tid1, &attr, say_hello1, ( void* )&index1 );
    if( ret != 0 )
    {
        cout << "pthread_create error:error_code=" << ret << endl;
    }
    int index2 = 2;
    ret = pthread_create( &tid2, &attr, say_hello2, ( void* )&index2 );
    if( ret != 0 )
    {
        cout << "pthread_create error:error_code=" << ret << endl;
    }
    pthread_join( tid1, NULL ); //连接两个线程
    pthread_join( tid2, NULL );
    pthread_attr_destroy( &attr ); //释放内存
    pthread_mutex_destroy( &tasks_mutex ); //注销锁
    pthread_cond_destroy( &tasks_cond ); //正常退出
}