Redis的模块化开发设计的还是相当不错的，在Bio.h和Bio.c文件中定义了一个多线程的文件任务处理模块，在添加和处理任务的时候使用互斥锁和条件变量进行的同步，而且本身也支持多线程，这个模块的支持两个类型，一个是关闭文件，另一个是将内存中的数据刷新到磁盘中去，也算是数据持久化的一部分了。其中三个宏定义了这些数据。
#define REDIS_BIO_CLOSE_FILE 0 /*关闭一个系统调用*/#define REDIS_BIO_AOF_FSYNC 1 /*文件数据刷新到磁盘*/#define REDIS_BIO_NUM_OPS 2/*支持任务类型数*/
模块的基础变量数据：
static pthread_t bio_threads[REDIS_BIO_NUM_OPS];/*多线程情况下线程的个数*/static pthread_mutex_t bio_mutex[REDIS_BIO_NUM_OPS];/*互斥锁*/static pthread_cond_t bio_condvar[REDIS_BIO_NUM_OPS];/*条件变量*/static list *bio_jobs[REDIS_BIO_NUM_OPS];/*后台任务链表，每个线程一个，根据下标区分*/static unsigned long long bio_pending[REDIS_BIO_NUM_OPS];/*记录每个线程剩余的任务数*/struct bio_job { /*后台IO节点，任务是通过链表来维护的，这个算是链表内的节点数据，第一个是创建时间，第二个是指定参数。*/ time_t time; /* Time at which the job was created. */ /* Job specific arguments pointers. If we need to pass more than three * arguments we can just pass a pointer to a structure or alike. */ void *arg1, *arg2, *arg3;}; 具体的实现接口，注意，这个模块中.h和.c文件中定义的接口不一样，不知道是写错了还是怎么回事，.h中定义的部分接口没有实现：
void bioInit(void); /初始化变量数据和线程数据/void bioCreateBackgroundJob(int type, void *arg1, void *arg2, void *arg3);/*添加一个任务*/void *bioProcessBackgroundJobs(void *arg);/*处理指定的任务数组*/unsigned long long bioPendingJobsOfType(int type);/*获取剩余的任务数*/void bioKillThreads(void);/*关闭线程*/
1.void bioInit(void);
void bioInit(void) { pthread_attr_t attr; pthread_t thread; size_t stacksize; int j; /*初始化条件变量和互斥锁*/ for (j = 0; j < REDIS_BIO_NUM_OPS; j++) { pthread_mutex_init(&bio_mutex[j],NULL); pthread_cond_init(&bio_condvar[j],NULL); bio_jobs[j] = listCreate(); bio_pending[j] = 0; } /*初始化线程属性，自动增加线程栈的大小*/ pthread_attr_init(&attr); pthread_attr_getstacksize(&attr,&stacksize); if (!stacksize) stacksize = 1; /* The world is full of Solaris Fixes */ while (stacksize < REDIS_THREAD_STACK_SIZE) stacksize *= 2; pthread_attr_setstacksize(&attr, stacksize); /* Ready to spawn our threads. We use the single argument the thread * function accepts in order to pass the job ID the thread is * responsible of. */ for (j = 0; j < REDIS_BIO_NUM_OPS; j++) { void *arg = (void*)(unsigned long) j; if (pthread_create(&thread,&attr,bioProcessBackgroundJobs,arg) != 0) { redisLog(REDIS_WARNING,"Fatal: Can't initialize Background Jobs."); exit(1); } bio_threads[j] = thread; }}//这个没啥可说的，无非是初始化同步的数据和线程数据 void bioCreateBackgroundJob(int type, void *arg1, void *arg2, void *arg3);/*添加一个任务*/
1 /*创建一个后台任务，创建任务支持多线程 2 添加事件和处理事件就像是消费者和生产者的问题一样，采用互斥和条件变量来控制 3 参数1是添加到哪个队列中，剩余是三个参数*/ 4 void bioCreateBackgroundJob(int type, void *arg1, void *arg2, void *arg3) 5 { 6 struct bio_job *job = zmalloc(sizeof(*job)); 7 8 job->time = time(NULL); 9 job->arg1 = arg1;10 job->arg2 = arg2;11 job->arg3 = arg3;12 /*添加的时候要注意并发问题，添加完了发个信号*/13 pthread_mutex_lock(&bio_mutex[type]);14 listAddNodeTail(bio_jobs[type],job);15 bio_pending[type]++;16 pthread_cond_signal(&bio_condvar[type]);17 pthread_mutex_unlock(&bio_mutex[type]);18 } void *bioProcessBackgroundJobs(void *arg);
/*事件消费函数*/void *bioProcessBackgroundJobs(void *arg) { struct bio_job *job; unsigned long type = (unsigned long) arg; sigset_t sigset; /* Make the thread killable at any time, so that bioKillThreads() * can work reliably. */ pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);/*设置线程为收到cancle信号马上退出*/ pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, NULL); pthread_mutex_lock(&bio_mutex[type]); /* Block SIGALRM so we are sure that only the main thread will * receive the watchdog signal. */ sigemptyset(&sigset); sigaddset(&sigset, SIGALRM); if (pthread_sigmask(SIG_BLOCK, &sigset, NULL)) redisLog(REDIS_WARNING, "Warning: can't mask SIGALRM in bio.c thread: %s", strerror(errno)); while(1) { listNode *ln; /* The loop always starts with the lock hold. */ if (listLength(bio_jobs[type]) == 0) { pthread_cond_wait(&bio_condvar[type],&bio_mutex[type]); continue; } /* Pop the job from the queue. */ ln = listFirst(bio_jobs[type]); job = ln->value; /* It is now possible to unlock the background system as we know have * a stand alone job structure to process.*/ pthread_mutex_unlock(&bio_mutex[type]); /*处理任务的时候解除互斥锁，提高效率*/ /* 区分任务类型，具体执行 */ if (type == REDIS_BIO_CLOSE_FILE) { close((long)job->arg1); } else if (type == REDIS_BIO_AOF_FSYNC) { aof_fsync((long)job->arg1); } else { redisPanic("Wrong job type in bioProcessBackgroundJobs()."); } zfree(job); /* Lock again before reiterating the loop, if there are no longer * jobs to process we'll block again in pthread_cond_wait(). */ pthread_mutex_lock(&bio_mutex[type]);/*修改公共资源的的是要加锁发，防止并发问题*/ listDelNode(bio_jobs[type],ln);/*删除节点，并减掉任务数*/ bio_pending[type]--; }} void bioKillThreads(void);/*关闭线程*/
1 void bioKillThreads(void) 2 { 3 int err, j; 4 5 for (j = 0; j < REDIS_BIO_NUM_OPS; j++) 6 { 7 if (pthread_cancel(bio_threads[j]) == 0) /*给线程发送结束信号，发送成功之后等待其结束*/ 8 { 9 if ((err = pthread_join(bio_threads[j],NULL)) != 0) 10 {11 redisLog(REDIS_WARNING,"Bio thread for job type #%d can be joined: %s",j, strerror(err));12 }13 else 14 {15 redisLog(REDIS_WARNING,"Bio thread for job type #%d terminated",j);16 }17 }18 }19 } 这个后台任务值负责关闭系统的调用和数据的持久化。