多线程+deque实现生产者消费者模型以及最终实现

创造两个线程分别充当生产者和消费者，生产者和消费者对同一个deque进行操作，生产者负责利用生产数据(deque : push_back )，消费者消费数据(deque : pop_back)。但是由于线程竞争资源的优先级是无法确定的，我们最终无法保证程序运行结束，deque始终为空.(如代码1)

#include<iostream>#include<stdlib.h>#include<unistd.h>#include<pthread.h>#include<time.h>#include<deque>#include<algorithm>#include<iterator>using namespace std;deque<int> dt;struct pcst{    pthread_mutex_t mutex;    pthread_cond_t not_full;    pthread_cond_t not_empty;}shared = {PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER,    PTHREAD_COND_INITIALIZER};void* producer(void *arg){    pthread_mutex_lock(&shared.mutex);    int count = 10;    while(count-- > 0)    {        srand(time(NULL));        dt.push_back(rand() % 256);        cout<<dt.back()<<" in"<<endl;        sleep(1);    }    pthread_cond_signal(&shared.not_empty);    pthread_mutex_unlock(&shared.mutex);}void* consumer(void *arg){    pthread_mutex_lock(&shared.mutex);    while(!dt.empty())    {        cout<<dt.back()<<" out"<<endl;        dt.pop_back();    }    cout<<"size: "<<dt.size()<<endl;    pthread_cond_signal(&shared.not_full);    pthread_mutex_unlock(&shared.mutex);}int main(int argc, char const* argv[]){    pthread_t p_id;    pthread_t c_id;    //生产者生产数据    pthread_create(&p_id, NULL, producer, NULL);    //消费者消费数据    pthread_create(&c_id, NULL, consumer, NULL);    //等待线程结束    pthread_join(p_id, NULL);    pthread_join(c_id, NULL);    return 0;}

当消费者程序先竞争到资源后，consumer先执行，导致生产者还未生产数据，消费者先消费数据.
为了解决这个问题，一些人可能设置线程属性中线程的优先级，保证生产者先生产数据，消费者再消费数据，如代码2

#include<iostream>#include<stdlib.h>#include<unistd.h>#include<pthread.h>#include<time.h>#include<deque>#include<algorithm>#include<iterator>using namespace std;struct shed_param{    int sched_priority;};deque<int> dt;struct pcst{    pthread_mutex_t mutex;    pthread_cond_t not_full;    pthread_cond_t not_empty;}shared = {PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER,    PTHREAD_COND_INITIALIZER};void* producer(void *arg){    pthread_mutex_lock(&shared.mutex);    int count = 10;    while(count-- > 0)    {        srand(time(NULL));        dt.push_back(rand() % 256);        cout<<dt.back()<<" in"<<endl;        sleep(1);    }    pthread_cond_signal(&shared.not_empty);    pthread_mutex_unlock(&shared.mutex);}void* consumer(void *arg){    pthread_mutex_lock(&shared.mutex);    while(!dt.empty())    {        cout<<dt.back()<<" out"<<endl;        dt.pop_back();    }    cout<<"size: "<<dt.size()<<endl;    pthread_cond_signal(&shared.not_full);    pthread_mutex_unlock(&shared.mutex);}int main(int argc, char const* argv[]){    pthread_t p_id;    pthread_t c_id;    //设置线程属性，生产者优先级高于消费者.    pthread_attr_t attr1, attr2;    pthread_attr_init(&attr1);    pthread_attr_init(&attr2);    struct sched_param sp1;    sp1.sched_priority = 0;    struct sched_param sp2;    sp2.sched_priority = 1;    pthread_attr_setschedpolicy(&attr1, SCHED_FIFO);    pthread_attr_setschedpolicy(&attr2, SCHED_FIFO);    pthread_attr_setschedparam(&attr1, &sp1);    pthread_attr_setschedparam(&attr2, &sp2);    //生产者生产数据    pthread_create(&p_id, &attr1, producer, NULL);    //消费者消费数据    pthread_create(&c_id, &attr2, consumer, NULL);    //等待线程结束    pthread_join(p_id, NULL);    pthread_join(c_id, NULL);    pthread_attr_destroy(&attr1);    pthread_attr_destroy(&attr2);    return 0;}

但是不可行

解释不可行的原因，总的来说，是调度问题，操作系统不能完全保证高优先级的线程先运行，但是我们可以通过线程间同步来解决这个问题：通过同步条件让某个线程等待(这里是让消费者线程先等待)，另外一个线程运行

//gdb会打乱线程的执行，真实环境下时间片等由操作系统决定//打日志,printf/cout不是线程安全的#include<iostream>#include<stdlib.h>#include<unistd.h>#include<pthread.h>#include<time.h>#include<deque>#include<algorithm>#include<iterator>using namespace std;deque<int> dt;struct pcst{    pthread_mutex_t mutex;    pthread_cond_t not_full;    pthread_cond_t not_empty;}shared = {PTHREAD_MUTEX_INITIALIZER, PTHREAD_COND_INITIALIZER,    PTHREAD_COND_INITIALIZER};void* producer(void *arg){    pthread_mutex_lock(&shared.mutex);    int count = 10;    while(count-- > 0)    {        srand(time(NULL));        dt.push_back(rand() % 256);        cout<<dt.back()<<" in"<<endl;        sleep(1);    }    pthread_cond_signal(&shared.not_empty);    pthread_mutex_unlock(&shared.mutex);}void* consumer(void *arg){    pthread_mutex_lock(&shared.mutex);    if(dt.empty())    {        pthread_cond_wait(&shared.not_empty, &shared.mutex);        pthread_mutex_unlock(&shared.mutex);    }    while(!dt.empty())    {        cout<<dt.front()<<" out"<<endl;        dt.pop_front();    }    cout<<"size: "<<dt.size()<<endl;    pthread_cond_signal(&shared.not_full);    pthread_mutex_unlock(&shared.mutex);}int main(int argc, char const* argv[]){    pthread_t p_id;    pthread_t c_id;    //设置线程属性，生产者优先级高于消费者.#if 0    pthread_attr_t attr1, attr2;    pthread_attr_init(&attr1);    pthread_attr_init(&attr2);    struct sched_param sp1;    sp1.sched_priority = 0;    struct sched_param sp2;    sp2.sched_priority = 1;    pthread_attr_setschedpolicy(&attr1, SCHED_FIFO);    pthread_attr_setschedpolicy(&attr2, SCHED_FIFO);    pthread_attr_setschedparam(&attr1, &sp1);    pthread_attr_setschedparam(&attr2, &sp2);#endif    //生产者生产数据    pthread_create(&p_id, NULL, producer, NULL);    //消费者消费数据    pthread_create(&c_id, NULL, consumer, NULL);    //等待线程结束    pthread_join(p_id, NULL);    pthread_join(c_id, NULL);#if 0    pthread_attr_destroy(&attr1);    pthread_attr_destroy(&attr2);#endif    return 0;}

这就是最终的代码
测试结果