多线程-读写锁

/*************************************************************************    > File Name: test.c    > Author: ndj    > Mail: [e-mail]    > Created Time: 2017年08月22日 星期二 10时34分52秒 ************************************************************************///作业请求队列由单个读写锁保护。多个工作线程获取单个主线程分配给他们的作业#include<stdio.h>#include<stdlib.h>#include<pthread.h>struct job{    struct job *j_next;    struct job *j_prev;    pthread_t j_id;//tells which thread handles this job    /*more stuff here*/    char *j_str;};//工作队列struct queue{    struct job *q_head;    struct job *q_tail;    pthread_rwlock_t q_lock;};struct queue job_queue;//工作队列, 全局变量。所以线程均可以访问/* * Initialize a queue */ int queue_init(struct queue *qp){    int err;    qp->q_head = NULL;    qp->q_tail = NULL;    err = pthread_rwlock_init(&qp->q_lock, NULL);//读写锁初始化    if(err != 0)        return err;    /*continue initialization*/    return 0;}/* * Inser a job at the head of the queue */void job_insert(struct queue *qp, struct job *jp){    pthread_rwlock_wrlock(&qp->q_lock);//给工作队列加写锁    jp->j_next = qp->q_head;    jp->j_prev = NULL;    if(qp->q_head != NULL)//队列不为空        qp->q_head->j_prev = jp;    else//队列为空        qp->q_tail = jp;    qp->q_head = jp;    pthread_rwlock_unlock(&qp->q_lock);//给工作队列解锁}/* * Append a job on the tail of the queue */void job_append(struct queue *qp, struct job *jp){    pthread_rwlock_wrlock(&qp->q_lock);//给工作队列加锁    //qp->q_tail->j_next = jp;    jp->j_next = NULL;    jp->j_prev = qp->q_tail;    if(qp->q_tail != NULL)//工作队列不为空        qp->q_tail->j_next = jp;    else        qp->q_head = jp;//工作队列为空    qp->q_tail = jp;    pthread_rwlock_unlock(&qp->q_lock);//给工作队列解锁}/* * Remove the given job from a queue */ void job_remove(struct queue *qp, struct job *jp){    pthread_rwlock_wrlock(&qp->q_lock);//给工作队列加写锁    if(jp == qp->q_head)//删除的工作是队头    {        qp->q_head = jp->j_next;        if(qp->q_tail == jp)            qp->q_tail = NULL;        else            jp->j_next->j_prev = jp->j_prev;    }    else if(jp == qp->q_tail)//删除队尾    {        qp->q_tail = jp->j_prev;        qp->q_tail->j_next = jp->j_next;    }    else    {        jp->j_prev->j_next = jp->j_next;        jp->j_next->j_prev = jp->j_prev;    }    pthread_rwlock_unlock(&qp->q_lock);//给工作队列解锁}/* *Find a job for the given thread ID */struct job* job_find(struct queue *qp, pthread_t  id){    struct job *jp;    if(pthread_rwlock_rdlock(&qp->q_lock) != 0)        return (NULL);//加读锁没有成功     for(jp = qp->q_head; jp != NULL; jp = jp->j_next)        if(pthread_equal(id, jp->j_id))            break;    pthread_rwlock_unlock(&qp->q_lock);//解锁    return (jp);}/* * 线程1函数 */ void* thrd_func1(void *arg){    //从队列中获取任务1    struct job *jp;    if((jp = job_find(&job_queue, 1)) != NULL)        printf("thread 1 get job 1 success\n");    else        printf("thread 1 get job 1 failed\n");    job_remove(&job_queue, jp);    printf("thread 1: %s\n", jp->j_str);    pthread_exit(NULL);}/* * 线程2函数 */void* thrd_func2(void *arg){    //从队列中获取任务2    struct job *jp;    if((jp = job_find(&job_queue, 2)) != NULL)        printf("thread 2 get job 2 success\n");    else        printf("thread 2 get job 2 failed\n");    job_remove(&job_queue, jp);    printf("thread 2: %s\n", jp->j_str);    pthread_exit(NULL);}/* * 线程3函数 */void* thrd_func3(void* arg){    //从队列中获取 任务3    struct job *jp;    if((jp = job_find(&job_queue, 3)) != NULL)        printf("thread 3 get job 3 success\n");    else        printf("thread 3 get job 3 failed\n");    job_remove(&job_queue, jp);    printf("thread 3: %s\n", jp->j_str);    pthread_exit(NULL);}int main(void){    int err;    //struct queue job_queue;//工作队列    pthread_t thread[3];//线程ID    struct job job[4] = {        {NULL, NULL, 1, "job 1"},        {NULL, NULL, 2, "job 2"},        {NULL, NULL, 3, "job 3"},        {NULL, NULL, 4, "job 4"}    };    int i;    /*工作队列初始化*/    if(queue_init(&job_queue) != 0)        printf("job queue  init failed\n");    else        printf("job queue init success\n");    for(i=0; i<4; i++)    {        job_insert(&job_queue, &job[i]);//向队列这添加任务    }    err = pthread_create(&thread[0], NULL, thrd_func1, NULL);//创建线程1    if(err != 0)        printf("thread 1 create failed\n");    else        printf("thread 1 create success\n");    err = pthread_create(&thread[1], NULL, thrd_func2,NULL);//创建线程2    if(err != 0)        printf("thread 2 create failed\n");    else        printf("thread 2 create success\n");    err = pthread_create(&thread[2], NULL, thrd_func3, NULL);//创建线程3    if(err != 0)        printf("thread 3 create failed\n");    else        printf("thread  3 create success\n");    for(i=0; i<3; i++)    {        err = pthread_join(thread[i], NULL);        if(err != 0)            printf("thread %d can't join\n", i);        else            printf("thread %d join\n", i);    }    exit(0);}