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// Copyright © Tavian Barnes <tavianator@tavianator.com>
// SPDX-License-Identifier: 0BSD
#include "ioq.h"
#include "dir.h"
#include "list.h"
#include "lock.h"
#include "sanity.h"
#include <assert.h>
#include <errno.h>
#include <pthread.h>
#include <stdbool.h>
#include <stdlib.h>
/**
* An I/O queue request.
*/
struct ioq_req {
/** Base file descriptor for openat(). */
int dfd;
/** Relative path to dfd. */
const char *path;
/** Arbitrary user data. */
void *ptr;
};
/**
* An I/O queue command.
*/
struct ioq_cmd {
union {
struct ioq_req req;
struct ioq_res res;
};
struct ioq_cmd *next;
};
/**
* An MPMC queue of I/O commands.
*/
struct ioqq {
pthread_mutex_t mutex;
pthread_cond_t cond;
bool stop;
struct ioq_cmd *head;
struct ioq_cmd **tail;
};
static struct ioqq *ioqq_create(void) {
struct ioqq *ioqq = malloc(sizeof(*ioqq));
if (!ioqq) {
goto fail;
}
if (mutex_init(&ioqq->mutex, NULL) != 0) {
goto fail_free;
}
if (cond_init(&ioqq->cond, NULL) != 0) {
goto fail_mutex;
}
ioqq->stop = false;
SLIST_INIT(ioqq);
return ioqq;
fail_mutex:
mutex_destroy(&ioqq->mutex);
fail_free:
free(ioqq);
fail:
return NULL;
}
/** Push a command onto the queue. */
static void ioqq_push(struct ioqq *ioqq, struct ioq_cmd *cmd) {
mutex_lock(&ioqq->mutex);
SLIST_APPEND(ioqq, cmd);
mutex_unlock(&ioqq->mutex);
cond_signal(&ioqq->cond);
}
/** Pop a command from a queue. */
static struct ioq_cmd *ioqq_pop(struct ioqq *ioqq) {
mutex_lock(&ioqq->mutex);
while (!ioqq->stop && !ioqq->head) {
cond_wait(&ioqq->cond, &ioqq->mutex);
}
struct ioq_cmd *cmd = SLIST_POP(ioqq);
mutex_unlock(&ioqq->mutex);
return cmd;
}
/** Pop a command from a queue without blocking. */
static struct ioq_cmd *ioqq_trypop(struct ioqq *ioqq) {
if (!mutex_trylock(&ioqq->mutex)) {
return NULL;
}
struct ioq_cmd *cmd = SLIST_POP(ioqq);
mutex_unlock(&ioqq->mutex);
return cmd;
}
/** Stop a queue, waking up any waiters. */
static void ioqq_stop(struct ioqq *ioqq) {
mutex_lock(&ioqq->mutex);
ioqq->stop = true;
mutex_unlock(&ioqq->mutex);
cond_broadcast(&ioqq->cond);
}
static void ioqq_destroy(struct ioqq *ioqq) {
if (ioqq) {
cond_destroy(&ioqq->cond);
mutex_destroy(&ioqq->mutex);
free(ioqq);
}
}
struct ioq {
/** The depth of the queue. */
size_t depth;
/** The current size of the queue. */
size_t size;
/** Pending I/O requests. */
struct ioqq *pending;
/** Ready I/O responses. */
struct ioqq *ready;
/** The number of background threads. */
size_t nthreads;
/** The background threads themselves. */
pthread_t *threads;
};
/** Background thread entry point. */
static void *ioq_work(void *ptr) {
struct ioq *ioq = ptr;
while (true) {
struct ioq_cmd *cmd = ioqq_pop(ioq->pending);
if (!cmd) {
break;
}
struct ioq_req req = cmd->req;
sanitize_uninit(cmd);
struct ioq_res *res = &cmd->res;
res->ptr = req.ptr;
res->dir = bfs_opendir(req.dfd, req.path);
res->error = errno;
ioqq_push(ioq->ready, cmd);
}
return NULL;
}
struct ioq *ioq_create(size_t depth, size_t threads) {
struct ioq *ioq = malloc(sizeof(*ioq));
if (!ioq) {
goto fail;
}
ioq->depth = depth;
ioq->size = 0;
ioq->pending = NULL;
ioq->ready = NULL;
ioq->nthreads = 0;
ioq->pending = ioqq_create();
if (!ioq->pending) {
goto fail;
}
ioq->ready = ioqq_create();
if (!ioq->ready) {
goto fail;
}
ioq->threads = malloc(threads * sizeof(ioq->threads[0]));
if (!ioq->threads) {
goto fail;
}
for (size_t i = 0; i < threads; ++i) {
errno = pthread_create(&ioq->threads[i], NULL, ioq_work, ioq);
if (errno != 0) {
goto fail;
}
++ioq->nthreads;
}
return ioq;
int err;
fail:
err = errno;
ioq_destroy(ioq);
errno = err;
return NULL;
}
int ioq_opendir(struct ioq *ioq, int dfd, const char *path, void *ptr) {
if (ioq->size >= ioq->depth) {
return -1;
}
struct ioq_cmd *cmd = malloc(sizeof(*cmd));
if (!cmd) {
return -1;
}
struct ioq_req *req = &cmd->req;
req->dfd = dfd;
req->path = path;
req->ptr = ptr;
++ioq->size;
ioqq_push(ioq->pending, cmd);
return 0;
}
struct ioq_res *ioq_pop(struct ioq *ioq) {
if (ioq->size == 0) {
return NULL;
}
struct ioq_cmd *cmd = ioqq_pop(ioq->ready);
if (!cmd) {
return NULL;
}
--ioq->size;
return &cmd->res;
}
struct ioq_res *ioq_trypop(struct ioq *ioq) {
if (ioq->size == 0) {
return NULL;
}
struct ioq_cmd *cmd = ioqq_trypop(ioq->ready);
if (!cmd) {
return NULL;
}
--ioq->size;
return &cmd->res;
}
void ioq_free(struct ioq *ioq, struct ioq_res *res) {
struct ioq_cmd *cmd = (struct ioq_cmd *)res;
free(cmd);
}
void ioq_destroy(struct ioq *ioq) {
if (!ioq) {
return;
}
if (ioq->pending) {
ioqq_stop(ioq->pending);
}
for (size_t i = 0; i < ioq->nthreads; ++i) {
if (pthread_join(ioq->threads[i], NULL) != 0) {
abort();
}
}
free(ioq->threads);
ioqq_destroy(ioq->ready);
ioqq_destroy(ioq->pending);
free(ioq);
}
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