/*
* Copyright (C) Igor Sysoev
* Copyright (C) NGINX, Inc.
*/
#include <nxt_main.h>
/*
* Available work items are crucial for overall engine operation, so
* the items are preallocated in two chunks: cache and spare chunks.
* By default each chunk preallocates 409 work items on two or four
* CPU pages depending on platform. If all items in a cache chunk are
* exhausted then a spare chunk becomes a cache chunk, and a new spare
* chunk is allocated. This two-step allocation mitigates low memory
* condition impact on work queue operation. However, if both chunks
* are exhausted then a thread will sleep in reliance on another thread
* frees some memory. However, this may lead to deadlock and probably
* a process should be aborted. This behaviour should be considered as
* abort on program stack exhaustion.
*
* The cache and spare chunks initially are also allocated in two steps:
* a spare chunk is allocated first, then it becomes the cache chunk and
* a new spare chunk is allocated again.
*/
static void nxt_work_queue_allocate(nxt_work_queue_cache_t *cache,
nxt_thread_spinlock_t *lock);
static void nxt_work_queue_sleep(nxt_thread_spinlock_t *lock);
static nxt_work_queue_t *nxt_thread_current_work_queue(nxt_thread_t *thr);
static nxt_work_handler_t nxt_locked_work_queue_pop_work(
nxt_locked_work_queue_t *lwq, void **obj, void **data, nxt_log_t **log);
/* It should be adjusted with the "work_queue_bucket_items" directive. */
static nxt_uint_t nxt_work_queue_bucket_items = 409;
void
nxt_thread_work_queue_create(nxt_thread_t *thr, size_t chunk_size)
{
nxt_memzero(&thr->work_queue, sizeof(nxt_thread_work_queue_t));
nxt_work_queue_name(&thr->work_queue.main, "main");
nxt_work_queue_name(&thr->work_queue.last, "last");
if (chunk_size == 0) {
chunk_size = nxt_work_queue_bucket_items;
}
/* nxt_work_queue_chunk_t already has one work item. */
thr->work_queue.cache.chunk_size = chunk_size - 1;
while (thr->work_queue.cache.next == NULL) {
nxt_work_queue_allocate(&thr->work_queue.cache, NULL);
}
}
void
nxt_thread_work_queue_destroy(nxt_thread_t *thr)
{
nxt_work_queue_chunk_t *chunk, *next;
for (chunk = thr->work_queue.cache.chunk; chunk; chunk = next) {
next = chunk->next;
nxt_free(chunk);
}
}
static void
nxt_work_queue_allocate(nxt_work_queue_cache_t *cache,
nxt_thread_spinlock_t *lock)
{
size_t size;
nxt_uint_t i, n;
nxt_work_t *work;
nxt_work_queue_chunk_t *chunk;
n = cache->chunk_size;
size = sizeof(nxt_work_queue_chunk_t) + n * sizeof(nxt_work_t);
chunk = nxt_malloc(size);
if (nxt_fast_path(chunk != NULL)) {
chunk->next = cache->chunk;
cache->chunk = chunk;
work = &chunk->work;
for (i = 0; i < n; i++) {
work[i].next = &work[i + 1];
}
work[i].next = NULL;
work++;
} else if (cache->spare != NULL) {
work = NULL;
} else {
nxt_work_queue_sleep(lock);
return;
}
cache->next = cache->spare;
cache->spare = work;
}
static void
nxt_work_queue_sleep(nxt_thread_spinlock_t *lock)
{
if (lock != NULL) {
nxt_thread_spin_unlock(lock);
}
nxt_nanosleep(100 * 1000000); /* 100ms */
if (lock != NULL) {
nxt_thread_spin_lock(lock);
}
}
/* Add a work to a work queue tail. */
void
nxt_thread_work_queue_add(nxt_thread_t *thr, nxt_work_queue_t *wq,
nxt_work_handler_t handler, void *obj, void *data, nxt_log_t *log)
{
nxt_work_t *work;
nxt_work_queue_attach(thr, wq);
for ( ;; ) {
work = thr->work_queue.cache.next;
if (nxt_fast_path(work != NULL)) {
thr->work_queue.cache.next = work->next;
work->next = NULL;
work->handler = handler;
work->obj = obj;
work->data = data;
work->log = log;
if (wq->tail != NULL) {
wq->tail->next = work;
} else {
wq->head = work;
}
wq->tail = work;
return;
}
nxt_work_queue_allocate(&thr->work_queue.cache, NULL);
}
}
/* Push a work to a work queue head. */
void
nxt_thread_work_queue_push(nxt_thread_t *thr, nxt_work_queue_t *wq,
nxt_work_handler_t handler, void *obj, void *data, nxt_log_t *log)
{
nxt_work_t *work;
nxt_work_queue_attach(thr, wq);
for ( ;; ) {
work = thr->work_queue.cache.next;
if (nxt_fast_path(work != NULL)) {
thr->work_queue.cache.next = work->next;
work->next = wq->head;
work->handler = handler;
work->obj = obj;
work->data = data;
work->log = log;
wq->head = work;
if (wq->tail == NULL) {
wq->tail = work;
}
return;
}
nxt_work_queue_allocate(&thr->work_queue.cache, NULL);
}
}
/* Attach a work queue to a thread work queue. */
void
nxt_work_queue_attach(nxt_thread_t *thr, nxt_work_queue_t *wq)
{
if (wq->next == NULL && wq != thr->work_queue.tail) {
if (thr->work_queue.tail != NULL) {
thr->work_queue.tail->next = wq;
} else {
thr->work_queue.head = wq;
}
thr->work_queue.tail = wq;
}
}
/* Pop a work from a thread work queue head. */
nxt_work_handler_t
nxt_thread_work_queue_pop(nxt_thread_t *thr, void **obj, void **data,
nxt_log_t **log)
{
nxt_work_t *work;
nxt_work_queue_t *wq;
wq = nxt_thread_current_work_queue(thr);
if (wq != NULL) {
work = wq->head;
if (work != NULL) {
wq->head = work->next;
if (work->next == NULL) {
wq->tail = NULL;
}
*obj = work->obj;
nxt_prefetch(*obj);
*data = work->data;
nxt_prefetch(*data);
work->next = thr->work_queue.cache.next;
thr->work_queue.cache.next = work;
*log = work->log;
#if (NXT_DEBUG)
if (work->handler == NULL) {
nxt_log_alert(thr->log, "null work handler");
nxt_abort();
}
#endif
return work->handler;
}
}
return NULL;
}
static nxt_work_queue_t *
nxt_thread_current_work_queue(nxt_thread_t *thr)
{
nxt_work_queue_t *wq, *next;
for (wq = thr->work_queue.head; wq != NULL; wq = next) {
if (wq->head != NULL) {
nxt_log_debug(thr->log, "work queue: %s", wq->name);
return wq;
}
/* Detach empty work queue. */
next = wq->next;
wq->next = NULL;
thr->work_queue.head = next;
}
thr->work_queue.tail = NULL;
return NULL;
}
/* Drop a work with specified data from a thread work queue. */
void
nxt_thread_work_queue_drop(nxt_thread_t *thr, void *data)
{
nxt_work_t *work, *prev, *next, **link;
nxt_work_queue_t *wq;
for (wq = thr->work_queue.head; wq != NULL; wq = wq->next) {
prev = NULL;
link = &wq->head;
for (work = wq->head; work != NULL; work = next) {
next = work->next;
if (data != work->obj) {
prev = work;
link = &work->next;
} else {
if (next == NULL) {
wq->tail = prev;
}
nxt_log_debug(thr->log, "work queue drop");
*link = next;
work->next = thr->work_queue.cache.next;
thr->work_queue.cache.next = work;
}
}
}
}
/* Add a work to the thread last work queue's tail. */
void
nxt_thread_last_work_queue_add(nxt_thread_t *thr, nxt_work_handler_t handler,
void *obj, void *data, nxt_log_t *log)
{
nxt_work_t *work;
for ( ;; ) {
work = thr->work_queue.cache.next;
if (nxt_fast_path(work != NULL)) {
thr->work_queue.cache.next = work->next;
work->next = NULL;
work->handler = handler;
work->obj = obj;
work->data = data;
work->log = log;
if (thr->work_queue.last.tail != NULL) {
thr->work_queue.last.tail->next = work;
} else {
thr->work_queue.last.head = work;
}
thr->work_queue.last.tail = work;
return;
}
nxt_work_queue_allocate(&thr->work_queue.cache, NULL);
}
}
/* Pop a work from the thread last work queue's head. */
nxt_work_handler_t
nxt_thread_last_work_queue_pop(nxt_thread_t *thr, void **obj, void **data,
nxt_log_t **log)
{
nxt_work_t *work;
work = thr->work_queue.last.head;
if (work != NULL) {
nxt_log_debug(thr->log, "work queue: %s", thr->work_queue.last.name);
thr->work_queue.last.head = work->next;
if (work->next == NULL) {
thr->work_queue.last.tail = NULL;
}
*obj = work->obj;
nxt_prefetch(*obj);
*data = work->data;
nxt_prefetch(*data);
work->next = thr->work_queue.cache.next;
thr->work_queue.cache.next = work;
*log = work->log;
#if (NXT_DEBUG)
if (work->handler == NULL) {
nxt_log_alert(thr->log, "null work handler");
nxt_abort();
}
#endif
return work->handler;
}
return NULL;
}
void
nxt_work_queue_destroy(nxt_work_queue_t *wq)
{
nxt_thread_t *thr;
nxt_work_queue_t *q;
thr = nxt_thread();
/* Detach from a thread work queue. */
if (thr->work_queue.head == wq) {
thr->work_queue.head = wq->next;
q = NULL;
goto found;
}
for (q = thr->work_queue.head; q != NULL; q = q->next) {
if (q->next == wq) {
q->next = wq->next;
goto found;
}
}
return;
found:
if (thr->work_queue.tail == wq) {
thr->work_queue.tail = q;
}
/* Move all queue's works to a thread work queue cache. */
if (wq->tail != NULL) {
wq->tail->next = thr->work_queue.cache.next;
}
if (wq->head != NULL) {
thr->work_queue.cache.next = wq->head;
}
}
/* Locked work queue operations. */
void
nxt_locked_work_queue_create(nxt_locked_work_queue_t *lwq, size_t chunk_size)
{
nxt_memzero(lwq, sizeof(nxt_locked_work_queue_t));
if (chunk_size == 0) {
chunk_size = nxt_work_queue_bucket_items;
}
lwq->cache.chunk_size = chunk_size;
while (lwq->cache.next == NULL) {
nxt_work_queue_allocate(&lwq->cache, NULL);
}
}
void
nxt_locked_work_queue_destroy(nxt_locked_work_queue_t *lwq)
{
nxt_work_queue_chunk_t *chunk, *next;
for (chunk = lwq->cache.chunk; chunk; chunk = next) {
next = chunk->next;
nxt_free(chunk);
}
}
/* Add a work to a locked work queue tail. */
void
nxt_locked_work_queue_add(nxt_locked_work_queue_t *lwq,
nxt_work_handler_t handler, void *obj, void *data, nxt_log_t *log)
{
nxt_work_t *work;
nxt_thread_spin_lock(&lwq->lock);
for ( ;; ) {
work = lwq->cache.next;
if (nxt_fast_path(work != NULL)) {
lwq->cache.next = work->next;
work->next = NULL;
work->handler = handler;
work->obj = obj;
work->data = data;
work->log = log;
if (lwq->tail != NULL) {
lwq->tail->next = work;
} else {
lwq->head = work;
}
lwq->tail = work;
break;
}
nxt_work_queue_allocate(&lwq->cache, &lwq->lock);
}
nxt_thread_spin_unlock(&lwq->lock);
}
/* Pop a work from a locked work queue head. */
nxt_work_handler_t
nxt_locked_work_queue_pop(nxt_locked_work_queue_t *lwq, void **obj,
void **data, nxt_log_t **log)
{
nxt_work_handler_t handler;
nxt_thread_spin_lock(&lwq->lock);
handler = nxt_locked_work_queue_pop_work(lwq, obj, data, log);
nxt_thread_spin_unlock(&lwq->lock);
return handler;
}
static nxt_work_handler_t
nxt_locked_work_queue_pop_work(nxt_locked_work_queue_t *lwq, void **obj,
void **data, nxt_log_t **log)
{
nxt_work_t *work;
work = lwq->head;
if (work == NULL) {
return NULL;
}
*obj = work->obj;
nxt_prefetch(*obj);
*data = work->data;
nxt_prefetch(*data);
lwq->head = work->next;
if (work->next == NULL) {
lwq->tail = NULL;
}
work->next = lwq->cache.next;
lwq->cache.next = work;
*log = work->log;
return work->handler;
}
/* Move all works from a locked work queue to a usual work queue. */
void
nxt_locked_work_queue_move(nxt_thread_t *thr, nxt_locked_work_queue_t *lwq,
nxt_work_queue_t *wq)
{
void *obj, *data;
nxt_log_t *log;
nxt_work_handler_t handler;
/* Locked work queue head can be tested without a lock. */
if (nxt_fast_path(lwq->head == NULL)) {
return;
}
nxt_thread_spin_lock(&lwq->lock);
for ( ;; ) {
handler = nxt_locked_work_queue_pop_work(lwq, &obj, &data, &log);
if (handler == NULL) {
break;
}
nxt_thread_work_queue_add(thr, wq, handler, obj, data, log);
}
nxt_thread_spin_unlock(&lwq->lock);
}
