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bio操作相关的实现，对于线程，互斥量，条件变量，也需要理解清楚哦：
#include "server.h"
#include "bio.h"static pthread_t bio_threads[BIO_NUM_OPS];
static pthread_mutex_t bio_mutex[BIO_NUM_OPS];
static pthread_cond_t bio_newjob_cond[BIO_NUM_OPS];
static pthread_cond_t bio_step_cond[BIO_NUM_OPS];
static list *bio_jobs[BIO_NUM_OPS];
/* The following array is used to hold the number of pending jobs for every* OP type. This allows us to export the bioPendingJobsOfType() API that is* useful when the main thread wants to perform some operation that may involve* objects shared with the background thread. The main thread will just wait* that there are no longer jobs of this type to be executed before performing* the sensible operation. This data is also useful for reporting. */
static unsigned long long bio_pending[BIO_NUM_OPS];/* This structure represents a background Job. It is only used locally to this* file as the API does not expose the internals at all. */
struct bio_job {time_t time; /* Time at which the job was created. *//* Job specific arguments.*/int fd; /* Fd for file based background jobs */lazy_free_fn *free_fn; /* Function that will free the provided arguments */void *free_args[]; /* List of arguments to be passed to the free function */
};void *bioProcessBackgroundJobs(void *arg);/* Make sure we have enough stack to perform all the things we do in the* main thread. */
#define REDIS_THREAD_STACK_SIZE (1024*1024*4)/* Initialize the background system, spawning the thread. */
void bioInit(void) {pthread_attr_t attr;pthread_t thread;size_t stacksize;int j;/* Initialization of state vars and objects */for (j = 0; j < BIO_NUM_OPS; j++) {pthread_mutex_init(&bio_mutex[j],NULL);pthread_cond_init(&bio_newjob_cond[j],NULL);pthread_cond_init(&bio_step_cond[j],NULL);bio_jobs[j] = listCreate();bio_pending[j] = 0;}/* Set the stack size as by default it may be small in some system */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 < BIO_NUM_OPS; j++) {void *arg = (void*)(unsigned long) j;if (pthread_create(&thread,&attr,bioProcessBackgroundJobs,arg) != 0) {serverLog(LL_WARNING,"Fatal: Can't initialize Background Jobs.");exit(1);}bio_threads[j] = thread;}
}void bioSubmitJob(int type, struct bio_job *job) {job->time = time(NULL);pthread_mutex_lock(&bio_mutex[type]);listAddNodeTail(bio_jobs[type],job);bio_pending[type]++;pthread_cond_signal(&bio_newjob_cond[type]);pthread_mutex_unlock(&bio_mutex[type]);
}void bioCreateLazyFreeJob(lazy_free_fn free_fn, int arg_count, ...) {va_list valist;/* Allocate memory for the job structure and all required* arguments */struct bio_job *job = zmalloc(sizeof(*job) + sizeof(void *) * (arg_count));job->free_fn = free_fn;va_start(valist, arg_count);for (int i = 0; i < arg_count; i++) {job->free_args[i] = va_arg(valist, void *);}va_end(valist);bioSubmitJob(BIO_LAZY_FREE, job);
}void bioCreateCloseJob(int fd) {struct bio_job *job = zmalloc(sizeof(*job));job->fd = fd;bioSubmitJob(BIO_CLOSE_FILE, job);
}void bioCreateFsyncJob(int fd) {struct bio_job *job = zmalloc(sizeof(*job));job->fd = fd;bioSubmitJob(BIO_AOF_FSYNC, job);
}void *bioProcessBackgroundJobs(void *arg) {struct bio_job *job;unsigned long type = (unsigned long) arg;sigset_t sigset;/* Check that the type is within the right interval. */if (type >= BIO_NUM_OPS) {serverLog(LL_WARNING,"Warning: bio thread started with wrong type %lu",type);return NULL;}switch (type) {case BIO_CLOSE_FILE:redis_set_thread_title("bio_close_file");break;case BIO_AOF_FSYNC:redis_set_thread_title("bio_aof_fsync");break;case BIO_LAZY_FREE:redis_set_thread_title("bio_lazy_free");break;}redisSetCpuAffinity(server.bio_cpulist);makeThreadKillable();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))serverLog(LL_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_newjob_cond[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]);/* Process the job accordingly to its type. */if (type == BIO_CLOSE_FILE) {close(job->fd);} else if (type == BIO_AOF_FSYNC) {/* The fd may be closed by main thread and reused for another* socket, pipe, or file. We just ignore these errno because* aof fsync did not really fail. */if (redis_fsync(job->fd) == -1 &&errno != EBADF && errno != EINVAL){int last_status;atomicGet(server.aof_bio_fsync_status,last_status);atomicSet(server.aof_bio_fsync_status,C_ERR);atomicSet(server.aof_bio_fsync_errno,errno);if (last_status == C_OK) {serverLog(LL_WARNING,"Fail to fsync the AOF file: %s",strerror(errno));}} else {atomicSet(server.aof_bio_fsync_status,C_OK);}} else if (type == BIO_LAZY_FREE) {job->free_fn(job->free_args);} else {serverPanic("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]);listDelNode(bio_jobs[type],ln);bio_pending[type]--;/* Unblock threads blocked on bioWaitStepOfType() if any. */pthread_cond_broadcast(&bio_step_cond[type]);}
}/* Return the number of pending jobs of the specified type. */
unsigned long long bioPendingJobsOfType(int type) {unsigned long long val;pthread_mutex_lock(&bio_mutex[type]);val = bio_pending[type];pthread_mutex_unlock(&bio_mutex[type]);return val;
}/* If there are pending jobs for the specified type, the function blocks* and waits that the next job was processed. Otherwise the function* does not block and returns ASAP.** The function returns the number of jobs still to process of the* requested type.** This function is useful when from another thread, we want to wait* a bio.c thread to do more work in a blocking way.*/
unsigned long long bioWaitStepOfType(int type) {unsigned long long val;pthread_mutex_lock(&bio_mutex[type]);val = bio_pending[type];if (val != 0) {pthread_cond_wait(&bio_step_cond[type],&bio_mutex[type]);val = bio_pending[type];}pthread_mutex_unlock(&bio_mutex[type]);return val;
}/* Kill the running bio threads in an unclean way. This function should be* used only when it's critical to stop the threads for some reason.* Currently Redis does this only on crash (for instance on SIGSEGV) in order* to perform a fast memory check without other threads messing with memory. */
void bioKillThreads(void) {int err, j;for (j = 0; j < BIO_NUM_OPS; j++) {if (bio_threads[j] == pthread_self()) continue;if (bio_threads[j] && pthread_cancel(bio_threads[j]) == 0) {if ((err = pthread_join(bio_threads[j],NULL)) != 0) {serverLog(LL_WARNING,"Bio thread for job type #%d can not be joined: %s",j, strerror(err));} else {serverLog(LL_WARNING,"Bio thread for job type #%d terminated",j);}}}
}
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