线程之间的通信：
1、 互斥量
用的api函数有：pthread_mutex_init、pthread_mutex_lock、pthread_mutex_unlock、pthread_mutex_trylock
示例:
//thread_mutex.cpp#include <iostream>#include<queue>#include <unistd.h>#include <stdlib.h>#include <pthread.h>#include<signal.h>using namespace std;typedef unsigned int u32;typedef unsigned char byte;bool flag_exit = false;char *data ="test pthread mutex!";typedef struct job{u32 id;u32 len;byte data[1];}JOB,*PJOB;queue<PJOB> g_thrd_queue;pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;typedef void (*sighandler_t)(int);void handlesignal(int signal){cout << "+++handlesignal+++" << endl;flag_exit = true;}PJOB packjob(u32 id,byte *pdata,u32 len ){PJOB pret = NULL;int size = sizeof(JOB) + len;pret = (PJOB)malloc(size);if(pret != NULL){memset(pret,0,size);pret->id = id;pret->len = size;memcpy(pret->data,pdata,len);}return pret;}typedef void* (*pthrd_fun)(void*);void * thrd_function_1(void *parg){int iexit;PJOB pjob;int count = 0;cout << "thrd id is: " << pthread_self() << " run..." << endl;while(!flag_exit){pjob = packjob(count++,(byte*)data,strlen(data));//锁定互斥体pthread_mutex_lock(&mutex);g_thrd_queue.push(pjob);//解除互斥体pthread_mutex_unlock(&mutex);//睡眠2秒中sleep(1);}cout << "thrd id is: " << pthread_self() << " exit!" << endl;iexit = 0;pthread_exit(&iexit);}void * thrd_function_2(void *parg){int iexit;PJOB pjob;cout << "thrd id is: " << pthread_self() << " run..." << endl;while(!flag_exit){//锁定互斥体pthread_mutex_lock(&mutex);pjob = g_thrd_queue.front();g_thrd_queue.pop();//解除互斥体pthread_mutex_unlock(&mutex);cout << "id :"<<pjob->id << endl;cout <<"len :"<< pjob->len << endl;cout <<"data :" << (char*) pjob->data << endl;//释放内存free(pjob);//睡眠2秒中sleep(1);}cout << "thrd id is: " << pthread_self() << " exit!" << endl;iexit = 0;pthread_exit(&iexit);}int main(int argc,char *argv[]){pthread_t thread_id1;pthread_t thread_id2;int iret;cout << "pid id is: " << getpid() << endl;//安置信号处理函数signal(SIGUSR1,handlesignal);iret = pthread_create(&thread_id1,NULL,thrd_function_1,NULL);if(iret != 0){iret = 1;}iret = pthread_create(&thread_id2,NULL,thrd_function_2,NULL);if(iret != 0){iret = 1;}//等待子线程的退出pthread_join(thread_id1,NULL);pthread_join(thread_id2,NULL);//释放内存while(!g_thrd_queue.empty()){PJOB pjob;pjob = g_thrd_queue.front();g_thrd_queue.pop();free(pjob);}cout << "main thread is exit!" << endl;return iret;}
注意：有时候我们需要检测一个互斥体的状态却不希望被阻塞，那么我们就可以pthread_mutex_trylock。当你对一个解锁状态的互斥体调用pthread_mutex_trylock 时，就如调用pthread_mutex_lock 一样会锁定这个互斥体；pthread_mutex_trylock 会返回 0。 而当互斥体已经被其它线程锁定的时候，pthread_mutex_trylock 不会阻塞。相应的，pthread_mutex_trylock 会返回错误码EBUSY。持有锁的其它线程不会受到影响。你可以稍后再次尝试锁定这个互斥体
2、 信号量
用的api函数有：sem_init、sem_wait、sem_post、sem_destory、sem_trywait
示例:
#include<iostream>#include<queue>//thread_sem.cc#include<unistd.h>#include<stdlib.h>#include<pthread.h>#include<signal.h>#include<semaphore.h>using namespace std;typedef unsigned int u32;typedef unsigned char byte;bool flag_exit = false;char *data ="test pthread mutex!";typedef struct job{u32 id;u32 len;byte data[1];}JOB,*PJOB;queue<PJOB> g_thrd_queue;pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;sem_t sem_job_count;typedef void (*sighandler_t)(int);void handlesignal(int signal){cout << "+++handlesignal+++" << endl;flag_exit = true;}PJOB packjob(u32 id,byte *pdata,u32 len ){PJOB pret = NULL;int size = sizeof(JOB) + len;pret = (PJOB)malloc(size);if(pret != NULL){memset(pret,0,size);pret->id = id;pret->len = size;memcpy(pret->data,pdata,len);}return pret;}typedef void* (*pthrd_fun)(void*);void * thrd_function_1(void *parg){int iexit;PJOB pjob;int count = 0;cout << "thrd id is: " << pthread_self() << " run..." << endl;while(!flag_exit){pjob = packjob(count++,(byte*)data,strlen(data));//锁定互斥体pthread_mutex_lock(&mutex);g_thrd_queue.push(pjob);//信号量值+1sem_post(&sem_job_count);//解除互斥体pthread_mutex_unlock(&mutex);}cout << "thrd id is: " << pthread_self() << " exit!" << endl;iexit = 0;pthread_exit(&iexit);}void * thrd_function_2(void *parg){int iexit;PJOB pjob;cout << "thrd id is: " << pthread_self() << " run..." << endl;while(!flag_exit){//等待信号量+1sem_wait(&sem_job_count);//锁定互斥体pthread_mutex_lock(&mutex);pjob = g_thrd_queue.front();g_thrd_queue.pop();//解除互斥体pthread_mutex_unlock(&mutex);cout << "id :"<<pjob->id << endl;cout <<"len :"<< pjob->len << endl;cout <<"data :" << (char*) pjob->data << endl;//释放内存free(pjob);}cout << "thrd id is: " << pthread_self() << " exit!" << endl;iexit = 0;pthread_exit(&iexit);}int main(int argc,char *argv[]){pthread_t thread_id1;pthread_t thread_id2;int iret;cout << "pid id is: " << getpid() << endl;//安置信号处理函数signal(SIGUSR1,handlesignal);//初始化信号量sem_init(&sem_job_count,0,0);iret = pthread_create(&thread_id1,NULL,thrd_function_1,NULL);if(iret != 0){iret = 1;}iret = pthread_create(&thread_id2,NULL,thrd_function_2,NULL);if(iret != 0){iret = 1;}//等待子线程的退出pthread_join(thread_id1,NULL);pthread_join(thread_id2,NULL);//释放内存while(!g_thrd_queue.empty()){PJOB pjob;pjob = g_thrd_queue.front();g_thrd_queue.pop();free(pjob);}cout << "main thread is exit!" << endl;return iret;}
注意：sem_trywait和pthread_mutex_trylock用法类似。
3、 条件变量
用的api函数有：pthread_cond_init、用pthread_cond_signal、pthread_cond_wait、，pthread_cond_broadcast、pthread_cond_destroy
示例:
//thread_con.cc#include<iostream>#include<queue>#include<unistd.h>#include<stdlib.h>#include<pthread.h>#include<signal.h>#include<semaphore.h>using namespace std;typedef unsigned int u32;typedef unsigned char byte;bool flag_exit = false;char *data ="test pthread mutex!";typedef struct job{u32 id;u32 len;byte data[1];}JOB,*PJOB;queue<PJOB> g_thrd_queue;pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;pthread_cond_t g_thread_flag_cv;typedef void (*sighandler_t)(int);void handlesignal(int signal){cout << "+++handlesignal+++" << endl;flag_exit = true;}PJOB packjob(u32 id,byte *pdata,u32 len ){PJOB pret = NULL;int size = sizeof(JOB) + len;pret = (PJOB)malloc(size);if(pret != NULL){memset(pret,0,size);pret->id = id;pret->len = size;memcpy(pret->data,pdata,len);}return pret;}typedef void* (*pthrd_fun)(void*);void * thrd_function_1(void *parg){int iexit;PJOB pjob;int count = 0;cout << "thrd id is: " << pthread_self() << " run..." << endl;//锁定互斥体pthread_mutex_lock(&mutex);while(count <10){pjob = packjob(count++,(byte*)data,strlen(data));g_thrd_queue.push(pjob);}flag_exit = true;//触发条件变量pthread_cond_signal(&g_thread_flag_cv);//解除互斥体pthread_mutex_unlock(&mutex);cout << "thrd id is: " << pthread_self() << " exit!" << endl;iexit = 0;pthread_exit(&iexit);}void * thrd_function_2(void *parg){int iexit;PJOB pjob;cout << "thrd id is: " << pthread_self() << " run..." << endl;//锁定互斥体pthread_mutex_lock(&mutex);//等待条件变量while(!flag_exit)pthread_cond_wait(&g_thread_flag_cv,&mutex);while(!g_thrd_queue.empty()){pjob = g_thrd_queue.front();g_thrd_queue.pop();cout << "id :"<<pjob->id << endl;cout <<"len :"<< pjob->len << endl;cout <<"data :" << (char*) pjob->data << endl;//释放内存free(pjob);} //解除互斥体 pthread_mutex_unlock(&mutex);cout << "thrd id is: " << pthread_self() << " exit!" << endl;iexit = 0;pthread_exit(&iexit);}int main(int argc,char *argv[]){pthread_t thread_id1;pthread_t thread_id2;int iret;cout << "pid id is: " << getpid() << endl;//安置信号处理函数signal(SIGUSR1,handlesignal);//初始化条件量pthread_cond_init(&g_thread_flag_cv,NULL);iret = pthread_create(&thread_id1,NULL,thrd_function_1,NULL);if(iret != 0){iret = 1;}iret = pthread_create(&thread_id2,NULL,thrd_function_2,NULL);if(iret != 0){iret = 1;}//等待子线程的退出pthread_join(thread_id1,NULL);pthread_join(thread_id2,NULL);//释放内存while(!g_thrd_queue.empty()){PJOB pjob;pjob = g_thrd_queue.front();g_thrd_queue.pop();free(pjob);}pthread_cond_destroy(&g_thread_flag_cv);cout << "main thread is exit!" << endl;return iret;}
注意：pthread_cond_broadcast 函数会将所有等待该条件变量的线程解锁而不是
仅仅解锁一个线程。
问候不一定要慎重其事，但一定要真诚感人
