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+/* Background I/O service for Redis.
+ *
+ * This file implements operations that we need to perform in the background.
+ * Currently there is only a single operation, that is a background close(2)
+ * system call. This is needed as when the process is the last owner of a
+ * reference to a file closing it means unlinking it, and the deletion of the
+ * file is slow, blocking the server.
+ *
+ * In the future we'll either continue implementing new things we need or
+ * we'll switch to libeio. However there are probably long term uses for this
+ * file as we may want to put here Redis specific background tasks (for instance
+ * it is not impossible that we'll need a non blocking FLUSHDB/FLUSHALL
+ * implementation).
+ *
+ * DESIGN
+ * ------
+ *
+ * The design is trivial, we have a structure representing a job to perform
+ * and a different thread and job queue for every job type.
+ * Every thread waits for new jobs in its queue, and process every job
+ * sequentially.
+ *
+ * Jobs of the same type are guaranteed to be processed from the least
+ * recently inserted to the most recently inserted (older jobs processed
+ * first).
+ *
+ * Currently there is no way for the creator of the job to be notified about
+ * the completion of the operation, this will only be added when/if needed.
+ *
+ * ----------------------------------------------------------------------------
+ *
+ * Copyright (c) 2009-2012, Salvatore Sanfilippo <antirez at gmail dot com>
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * * Redistributions of source code must retain the above copyright notice,
+ * this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ * * Neither the name of Redis nor the names of its contributors may be used
+ * to endorse or promote products derived from this software without
+ * specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+
+#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. */
+typedef union bio_job {
+ /* Job specific arguments.*/
+ struct {
+ int fd; /* Fd for file based background jobs */
+ unsigned need_fsync:1; /* A flag to indicate that a fsync is required before
+ * the file is closed. */
+ } fd_args;
+
+ struct {
+ 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 */
+ } free_args;
+} bio_job;
+
+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, bio_job *job) {
+ 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 */
+ bio_job *job = zmalloc(sizeof(*job) + sizeof(void *) * (arg_count));
+ job->free_args.free_fn = free_fn;
+
+ va_start(valist, arg_count);
+ for (int i = 0; i < arg_count; i++) {
+ job->free_args.free_args[i] = va_arg(valist, void *);
+ }
+ va_end(valist);
+ bioSubmitJob(BIO_LAZY_FREE, job);
+}
+
+void bioCreateCloseJob(int fd, int need_fsync) {
+ bio_job *job = zmalloc(sizeof(*job));
+ job->fd_args.fd = fd;
+ job->fd_args.need_fsync = need_fsync;
+
+ bioSubmitJob(BIO_CLOSE_FILE, job);
+}
+
+void bioCreateFsyncJob(int fd) {
+ bio_job *job = zmalloc(sizeof(*job));
+ job->fd_args.fd = fd;
+
+ bioSubmitJob(BIO_AOF_FSYNC, job);
+}
+
+void *bioProcessBackgroundJobs(void *arg) {
+ 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) {
+ if (job->fd_args.need_fsync) {
+ redis_fsync(job->fd_args.fd);
+ }
+ close(job->fd_args.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_args.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_args.free_fn(job->free_args.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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