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// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright (C) 2017 Oracle. All Rights Reserved.
* Author: Darrick J. Wong <darrick.wong@oracle.com>
*/
#include <pthread.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <errno.h>
#include <assert.h>
#include <urcu.h>
#include "workqueue.h"
/* Main processing thread */
static void *
workqueue_thread(void *arg)
{
struct workqueue *wq = arg;
struct workqueue_item *wi;
/*
* Loop pulling work from the passed in work queue.
* Check for notification to exit after every chunk of work.
*/
rcu_register_thread();
while (1) {
pthread_mutex_lock(&wq->lock);
/*
* Wait for work.
*/
while (wq->next_item == NULL && !wq->terminate) {
assert(wq->item_count == 0);
pthread_cond_wait(&wq->wakeup, &wq->lock);
}
if (wq->next_item == NULL && wq->terminate) {
pthread_mutex_unlock(&wq->lock);
break;
}
/*
* Dequeue work from the head of the list. If the queue was
* full then send a wakeup if we're configured to do so.
*/
assert(wq->item_count > 0);
if (wq->max_queued)
pthread_cond_broadcast(&wq->queue_full);
wi = wq->next_item;
wq->next_item = wi->next;
wq->item_count--;
if (wq->max_queued && wq->next_item) {
/* more work, wake up another worker */
pthread_cond_signal(&wq->wakeup);
}
pthread_mutex_unlock(&wq->lock);
(wi->function)(wi->queue, wi->index, wi->arg);
free(wi);
}
rcu_unregister_thread();
return NULL;
}
/* Allocate a work queue and threads. Returns zero or negative error code. */
int
workqueue_create_bound(
struct workqueue *wq,
void *wq_ctx,
unsigned int nr_workers,
unsigned int max_queue)
{
unsigned int i;
int err = 0;
memset(wq, 0, sizeof(*wq));
err = -pthread_cond_init(&wq->wakeup, NULL);
if (err)
return err;
err = -pthread_cond_init(&wq->queue_full, NULL);
if (err)
goto out_wake;
err = -pthread_mutex_init(&wq->lock, NULL);
if (err)
goto out_cond;
wq->wq_ctx = wq_ctx;
wq->thread_count = nr_workers;
wq->max_queued = max_queue;
wq->threads = malloc(nr_workers * sizeof(pthread_t));
if (!wq->threads) {
err = -errno;
goto out_mutex;
}
wq->terminate = false;
wq->terminated = false;
for (i = 0; i < nr_workers; i++) {
err = -pthread_create(&wq->threads[i], NULL, workqueue_thread,
wq);
if (err)
break;
}
/*
* If we encounter errors here, we have to signal and then wait for all
* the threads that may have been started running before we can destroy
* the workqueue.
*/
if (err)
workqueue_destroy(wq);
return err;
out_mutex:
pthread_mutex_destroy(&wq->lock);
out_cond:
pthread_cond_destroy(&wq->queue_full);
out_wake:
pthread_cond_destroy(&wq->wakeup);
return err;
}
int
workqueue_create(
struct workqueue *wq,
void *wq_ctx,
unsigned int nr_workers)
{
return workqueue_create_bound(wq, wq_ctx, nr_workers, 0);
}
/*
* Create a work item consisting of a function and some arguments and schedule
* the work item to be run via the thread pool. Returns zero or a negative
* error code.
*/
int
workqueue_add(
struct workqueue *wq,
workqueue_func_t func,
uint32_t index,
void *arg)
{
struct workqueue_item *wi;
int ret;
assert(!wq->terminated);
if (wq->thread_count == 0) {
func(wq, index, arg);
return 0;
}
wi = malloc(sizeof(struct workqueue_item));
if (!wi)
return -errno;
wi->function = func;
wi->index = index;
wi->arg = arg;
wi->queue = wq;
wi->next = NULL;
/* Now queue the new work structure to the work queue. */
pthread_mutex_lock(&wq->lock);
restart:
if (wq->next_item == NULL) {
assert(wq->item_count == 0);
ret = -pthread_cond_signal(&wq->wakeup);
if (ret) {
pthread_mutex_unlock(&wq->lock);
free(wi);
return ret;
}
wq->next_item = wi;
} else {
/* throttle on a full queue if configured */
if (wq->max_queued && wq->item_count == wq->max_queued) {
pthread_cond_wait(&wq->queue_full, &wq->lock);
/*
* Queue might be empty or even still full by the time
* we get the lock back, so restart the lookup so we do
* the right thing with the current state of the queue.
*/
goto restart;
}
wq->last_item->next = wi;
}
wq->last_item = wi;
wq->item_count++;
pthread_mutex_unlock(&wq->lock);
return 0;
}
/*
* Wait for all pending work items to be processed and tear down the
* workqueue thread pool. Returns zero or a negative error code.
*/
int
workqueue_terminate(
struct workqueue *wq)
{
unsigned int i;
int ret;
pthread_mutex_lock(&wq->lock);
wq->terminate = true;
pthread_mutex_unlock(&wq->lock);
ret = -pthread_cond_broadcast(&wq->wakeup);
if (ret)
return ret;
for (i = 0; i < wq->thread_count; i++) {
ret = -pthread_join(wq->threads[i], NULL);
if (ret)
return ret;
}
pthread_mutex_lock(&wq->lock);
wq->terminated = true;
pthread_mutex_unlock(&wq->lock);
return 0;
}
/* Tear down the workqueue. */
void
workqueue_destroy(
struct workqueue *wq)
{
assert(wq->terminated);
free(wq->threads);
pthread_mutex_destroy(&wq->lock);
pthread_cond_destroy(&wq->wakeup);
pthread_cond_destroy(&wq->queue_full);
memset(wq, 0, sizeof(*wq));
}
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