简单的多线程流水线模型（二）

续上一篇《简单的多线程流水线模型（一）》

下面我们创建三个工人 Lucy,Lily,Lilei,他们干的活就是接收输入的秒数input,把睡眠input秒，然后把input-1丢给下一个工人。

这里做一下小结：

流水线模型的优缺点。

优点：一环扣一环，确保事情按顺序一个一个干完。

缺点：流水线的某个环节如果处理速度慢的话，会影响上游的整个流水线，所以流水线的瓶颈应该是花时间最多的那个环节。如何调度，这个后面再讨论。

下面的实现多个工人的流水线，这里是假设每个工人干的活差不多，实际使用的时候，可以为每个环节写不同的thread_worker,这样就可以做一些更灵活的工作了！

代码如下：

#include <pthread.h>#include <time.h>#include "errors.h"#define WORKERS_TOTAL 3struct worker_type{pthread_mutex_t  mtx;pthread_cond_t cond_has_input;pthread_cond_t cond_has_finished;int has_input;int has_finished;pthread_t thread_id;void * (*thread_worker)(void *);// The thread of this workerstruct worker_type * next;//below if optionally, corresponding to your demandschar *name;                     // The worker's nameint  input_data;                // The input data};typedef struct worker_type worker_t;typedef struct pipeline_type{int       count;    worker_t * head;    worker_t * tail;}pipeline_t;void * send_input_to_worker(worker_t *worker, int input){    //1. Catch the lockpthread_mutex_lock(&worker->mtx);//2. Waiting for the worker finish the jobwhile(!worker->has_finished){pthread_cond_wait(&worker->cond_has_finished,&worker->mtx);}//3. Pass the input to the worker.worker->has_input = 1;worker->has_finished = 0;worker->input_data = input;pthread_cond_signal(&worker->cond_has_input);//4. Unlockpthread_mutex_unlock(&worker->mtx);return NULL;}void * thread_worker(void *arg){    //1. Before looping ,do something initial.    worker_t * worker = (worker_t *)arg;    struct timespec t;int status;int input;t.tv_nsec = 0;//2. Looping    while(1){    //2.1 Lock the worker before access its valuepthread_mutex_lock(&worker->mtx);        //2.2 Waiting for the input    while(!worker->has_input){printf("%s: Give me the job!\n",worker->name);status = pthread_cond_wait(&worker->cond_has_input,&worker->mtx);}//2.3 Fetch the input,processinginput = worker->input_data;printf("%s: %d received! Process %d seconds\n",worker->name,input,input);sleep(input);//processif(worker->next != NULL){send_input_to_worker(worker->next,input-1);}else{printf("%s: Nobody works for me!\n",worker->name);}worker->has_input = 0;worker->has_finished = 1;//2.4 After processing, send the signal and unlock the mutexpthread_cond_signal(&worker->cond_has_finished);pthread_mutex_unlock(&worker->mtx);}}void *pipe_line_start(pipeline_t * pipeline_p){worker_t *worker_p, **worker_pp;char * names[] = {"Lucy ","Lily ","Lilei"};    int i;worker_pp = &pipeline_p->head;for(i = 0; i < WORKERS_TOTAL ;i++){*worker_pp = (worker_t *)malloc(sizeof(worker_t));worker_p = *worker_pp;worker_p->name = names[i];worker_p->thread_worker = thread_worker;worker_p->has_input = 0;worker_p->has_finished = 1;pthread_mutex_init(&worker_p->mtx,NULL);pthread_cond_init(&worker_p->cond_has_input,NULL);pthread_create(&worker_p->thread_id,NULL,worker_p->thread_worker,worker_p);worker_pp = &worker_p->next;}pipeline_p->tail = *worker_pp;worker_p->next = NULL;return NULL;}int main(int argc, char *argv[]){    int i;    pipeline_t pipeline1,;pipe_line_start(&pipeline1);while(1){scanf("%d",&i);send_input_to_worker(pipeline1.head,i);}pthread_exit(NULL);return 0;}

输出结果：

[hackooo@localhost c]$ gcc -lpthread ti.c 
[hackooo@localhost c]$ ./a.out 
Lilei: Give me the job!
Lily : Give me the job!
Lucy : Give me the job!
4
Lucy : 4 received! Process 4 seconds      //等待4秒
Lucy : Give me the job!
Lily : 3 received! Process 3 seconds        //等待3秒
Lily : Give me the job!
Lilei: 2 received! Process 2 seconds       //等待2秒
Lilei: Nobody works for me!
Lilei: Give me the job!
^C
[hackooo@localhost c]$