#include <linux/workqueue.h>
#include "async-thread.h"
-#define WORK_QUEUED_BIT 0
-#define WORK_DONE_BIT 1
-#define WORK_ORDER_DONE_BIT 2
-#define WORK_HIGH_PRIO_BIT 3
+#define WORK_DONE_BIT 0
+#define WORK_ORDER_DONE_BIT 1
+#define WORK_HIGH_PRIO_BIT 2
#define NO_THRESHOLD (-1)
#define DFT_THRESHOLD (32)
-/*
- * container for the kthread task pointer and the list of pending work
- * One of these is allocated per thread.
- */
-struct btrfs_worker_thread {
- /* pool we belong to */
- struct btrfs_workers *workers;
-
- /* list of struct btrfs_work that are waiting for service */
- struct list_head pending;
- struct list_head prio_pending;
-
- /* list of worker threads from struct btrfs_workers */
- struct list_head worker_list;
-
- /* kthread */
- struct task_struct *task;
-
- /* number of things on the pending list */
- atomic_t num_pending;
-
- /* reference counter for this struct */
- atomic_t refs;
-
- unsigned long sequence;
-
- /* protects the pending list. */
- spinlock_t lock;
-
- /* set to non-zero when this thread is already awake and kicking */
- int working;
-
- /* are we currently idle */
- int idle;
-};
-
-static int __btrfs_start_workers(struct btrfs_workers *workers);
-
-/*
- * btrfs_start_workers uses kthread_run, which can block waiting for memory
- * for a very long time. It will actually throttle on page writeback,
- * and so it may not make progress until after our btrfs worker threads
- * process all of the pending work structs in their queue
- *
- * This means we can't use btrfs_start_workers from inside a btrfs worker
- * thread that is used as part of cleaning dirty memory, which pretty much
- * involves all of the worker threads.
- *
- * Instead we have a helper queue who never has more than one thread
- * where we scheduler thread start operations. This worker_start struct
- * is used to contain the work and hold a pointer to the queue that needs
- * another worker.
- */
-struct worker_start {
- struct btrfs_work work;
- struct btrfs_workers *queue;
-};
-
-static void start_new_worker_func(struct btrfs_work *work)
-{
- struct worker_start *start;
- start = container_of(work, struct worker_start, work);
- __btrfs_start_workers(start->queue);
- kfree(start);
-}
-
-/*
- * helper function to move a thread onto the idle list after it
- * has finished some requests.
- */
-static void check_idle_worker(struct btrfs_worker_thread *worker)
-{
- if (!worker->idle && atomic_read(&worker->num_pending) <
- worker->workers->idle_thresh / 2) {
- unsigned long flags;
- spin_lock_irqsave(&worker->workers->lock, flags);
- worker->idle = 1;
-
- /* the list may be empty if the worker is just starting */
- if (!list_empty(&worker->worker_list) &&
- !worker->workers->stopping) {
- list_move(&worker->worker_list,
- &worker->workers->idle_list);
- }
- spin_unlock_irqrestore(&worker->workers->lock, flags);
- }
-}
-
-/*
- * helper function to move a thread off the idle list after new
- * pending work is added.
- */
-static void check_busy_worker(struct btrfs_worker_thread *worker)
-{
- if (worker->idle && atomic_read(&worker->num_pending) >=
- worker->workers->idle_thresh) {
- unsigned long flags;
- spin_lock_irqsave(&worker->workers->lock, flags);
- worker->idle = 0;
-
- if (!list_empty(&worker->worker_list) &&
- !worker->workers->stopping) {
- list_move_tail(&worker->worker_list,
- &worker->workers->worker_list);
- }
- spin_unlock_irqrestore(&worker->workers->lock, flags);
- }
-}
-
-static void check_pending_worker_creates(struct btrfs_worker_thread *worker)
-{
- struct btrfs_workers *workers = worker->workers;
- struct worker_start *start;
- unsigned long flags;
-
- rmb();
- if (!workers->atomic_start_pending)
- return;
-
- start = kzalloc(sizeof(*start), GFP_NOFS);
- if (!start)
- return;
-
- start->work.func = start_new_worker_func;
- start->queue = workers;
-
- spin_lock_irqsave(&workers->lock, flags);
- if (!workers->atomic_start_pending)
- goto out;
-
- workers->atomic_start_pending = 0;
- if (workers->num_workers + workers->num_workers_starting >=
- workers->max_workers)
- goto out;
-
- workers->num_workers_starting += 1;
- spin_unlock_irqrestore(&workers->lock, flags);
- btrfs_queue_worker(workers->atomic_worker_start, &start->work);
- return;
-
-out:
- kfree(start);
- spin_unlock_irqrestore(&workers->lock, flags);
-}
-
-static noinline void run_ordered_completions(struct btrfs_workers *workers,
- struct btrfs_work *work)
-{
- if (!workers->ordered)
- return;
-
- set_bit(WORK_DONE_BIT, &work->flags);
-
- spin_lock(&workers->order_lock);
-
- while (1) {
- if (!list_empty(&workers->prio_order_list)) {
- work = list_entry(workers->prio_order_list.next,
- struct btrfs_work, order_list);
- } else if (!list_empty(&workers->order_list)) {
- work = list_entry(workers->order_list.next,
- struct btrfs_work, order_list);
- } else {
- break;
- }
- if (!test_bit(WORK_DONE_BIT, &work->flags))
- break;
-
- /* we are going to call the ordered done function, but
- * we leave the work item on the list as a barrier so
- * that later work items that are done don't have their
- * functions called before this one returns
- */
- if (test_and_set_bit(WORK_ORDER_DONE_BIT, &work->flags))
- break;
-
- spin_unlock(&workers->order_lock);
-
- work->ordered_func(work);
-
- /* now take the lock again and drop our item from the list */
- spin_lock(&workers->order_lock);
- list_del(&work->order_list);
- spin_unlock(&workers->order_lock);
-
- /*
- * we don't want to call the ordered free functions
- * with the lock held though
- */
- work->ordered_free(work);
- spin_lock(&workers->order_lock);
- }
-
- spin_unlock(&workers->order_lock);
-}
-
-static void put_worker(struct btrfs_worker_thread *worker)
-{
- if (atomic_dec_and_test(&worker->refs))
- kfree(worker);
-}
-
-static int try_worker_shutdown(struct btrfs_worker_thread *worker)
-{
- int freeit = 0;
-
- spin_lock_irq(&worker->lock);
- spin_lock(&worker->workers->lock);
- if (worker->workers->num_workers > 1 &&
- worker->idle &&
- !worker->working &&
- !list_empty(&worker->worker_list) &&
- list_empty(&worker->prio_pending) &&
- list_empty(&worker->pending) &&
- atomic_read(&worker->num_pending) == 0) {
- freeit = 1;
- list_del_init(&worker->worker_list);
- worker->workers->num_workers--;
- }
- spin_unlock(&worker->workers->lock);
- spin_unlock_irq(&worker->lock);
-
- if (freeit)
- put_worker(worker);
- return freeit;
-}
-
-static struct btrfs_work *get_next_work(struct btrfs_worker_thread *worker,
- struct list_head *prio_head,
- struct list_head *head)
-{
- struct btrfs_work *work = NULL;
- struct list_head *cur = NULL;
-
- if (!list_empty(prio_head)) {
- cur = prio_head->next;
- goto out;
- }
-
- smp_mb();
- if (!list_empty(&worker->prio_pending))
- goto refill;
-
- if (!list_empty(head)) {
- cur = head->next;
- goto out;
- }
-
-refill:
- spin_lock_irq(&worker->lock);
- list_splice_tail_init(&worker->prio_pending, prio_head);
- list_splice_tail_init(&worker->pending, head);
-
- if (!list_empty(prio_head))
- cur = prio_head->next;
- else if (!list_empty(head))
- cur = head->next;
- spin_unlock_irq(&worker->lock);
-
- if (!cur)
- goto out_fail;
-
-out:
- work = list_entry(cur, struct btrfs_work, list);
-
-out_fail:
- return work;
-}
-
-/*
- * main loop for servicing work items
- */
-static int worker_loop(void *arg)
-{
- struct btrfs_worker_thread *worker = arg;
- struct list_head head;
- struct list_head prio_head;
- struct btrfs_work *work;
-
- INIT_LIST_HEAD(&head);
- INIT_LIST_HEAD(&prio_head);
-
- do {
-again:
- while (1) {
-
-
- work = get_next_work(worker, &prio_head, &head);
- if (!work)
- break;
-
- list_del(&work->list);
- clear_bit(WORK_QUEUED_BIT, &work->flags);
-
- work->worker = worker;
-
- work->func(work);
-
- atomic_dec(&worker->num_pending);
- /*
- * unless this is an ordered work queue,
- * 'work' was probably freed by func above.
- */
- run_ordered_completions(worker->workers, work);
-
- check_pending_worker_creates(worker);
- cond_resched();
- }
-
- spin_lock_irq(&worker->lock);
- check_idle_worker(worker);
-
- if (freezing(current)) {
- worker->working = 0;
- spin_unlock_irq(&worker->lock);
- try_to_freeze();
- } else {
- spin_unlock_irq(&worker->lock);
- if (!kthread_should_stop()) {
- cpu_relax();
- /*
- * we've dropped the lock, did someone else
- * jump_in?
- */
- smp_mb();
- if (!list_empty(&worker->pending) ||
- !list_empty(&worker->prio_pending))
- continue;
-
- /*
- * this short schedule allows more work to
- * come in without the queue functions
- * needing to go through wake_up_process()
- *
- * worker->working is still 1, so nobody
- * is going to try and wake us up
- */
- schedule_timeout(1);
- smp_mb();
- if (!list_empty(&worker->pending) ||
- !list_empty(&worker->prio_pending))
- continue;
-
- if (kthread_should_stop())
- break;
-
- /* still no more work?, sleep for real */
- spin_lock_irq(&worker->lock);
- set_current_state(TASK_INTERRUPTIBLE);
- if (!list_empty(&worker->pending) ||
- !list_empty(&worker->prio_pending)) {
- spin_unlock_irq(&worker->lock);
- set_current_state(TASK_RUNNING);
- goto again;
- }
-
- /*
- * this makes sure we get a wakeup when someone
- * adds something new to the queue
- */
- worker->working = 0;
- spin_unlock_irq(&worker->lock);
-
- if (!kthread_should_stop()) {
- schedule_timeout(HZ * 120);
- if (!worker->working &&
- try_worker_shutdown(worker)) {
- return 0;
- }
- }
- }
- __set_current_state(TASK_RUNNING);
- }
- } while (!kthread_should_stop());
- return 0;
-}
-
-/*
- * this will wait for all the worker threads to shutdown
- */
-void btrfs_stop_workers(struct btrfs_workers *workers)
-{
- struct list_head *cur;
- struct btrfs_worker_thread *worker;
- int can_stop;
-
- spin_lock_irq(&workers->lock);
- workers->stopping = 1;
- list_splice_init(&workers->idle_list, &workers->worker_list);
- while (!list_empty(&workers->worker_list)) {
- cur = workers->worker_list.next;
- worker = list_entry(cur, struct btrfs_worker_thread,
- worker_list);
-
- atomic_inc(&worker->refs);
- workers->num_workers -= 1;
- if (!list_empty(&worker->worker_list)) {
- list_del_init(&worker->worker_list);
- put_worker(worker);
- can_stop = 1;
- } else
- can_stop = 0;
- spin_unlock_irq(&workers->lock);
- if (can_stop)
- kthread_stop(worker->task);
- spin_lock_irq(&workers->lock);
- put_worker(worker);
- }
- spin_unlock_irq(&workers->lock);
-}
-
-/*
- * simple init on struct btrfs_workers
- */
-void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max,
- struct btrfs_workers *async_helper)
-{
- workers->num_workers = 0;
- workers->num_workers_starting = 0;
- INIT_LIST_HEAD(&workers->worker_list);
- INIT_LIST_HEAD(&workers->idle_list);
- INIT_LIST_HEAD(&workers->order_list);
- INIT_LIST_HEAD(&workers->prio_order_list);
- spin_lock_init(&workers->lock);
- spin_lock_init(&workers->order_lock);
- workers->max_workers = max;
- workers->idle_thresh = 32;
- workers->name = name;
- workers->ordered = 0;
- workers->atomic_start_pending = 0;
- workers->atomic_worker_start = async_helper;
- workers->stopping = 0;
-}
-
-/*
- * starts new worker threads. This does not enforce the max worker
- * count in case you need to temporarily go past it.
- */
-static int __btrfs_start_workers(struct btrfs_workers *workers)
-{
- struct btrfs_worker_thread *worker;
- int ret = 0;
-
- worker = kzalloc(sizeof(*worker), GFP_NOFS);
- if (!worker) {
- ret = -ENOMEM;
- goto fail;
- }
-
- INIT_LIST_HEAD(&worker->pending);
- INIT_LIST_HEAD(&worker->prio_pending);
- INIT_LIST_HEAD(&worker->worker_list);
- spin_lock_init(&worker->lock);
-
- atomic_set(&worker->num_pending, 0);
- atomic_set(&worker->refs, 1);
- worker->workers = workers;
- worker->task = kthread_create(worker_loop, worker,
- "btrfs-%s-%d", workers->name,
- workers->num_workers + 1);
- if (IS_ERR(worker->task)) {
- ret = PTR_ERR(worker->task);
- goto fail;
- }
-
- spin_lock_irq(&workers->lock);
- if (workers->stopping) {
- spin_unlock_irq(&workers->lock);
- ret = -EINVAL;
- goto fail_kthread;
- }
- list_add_tail(&worker->worker_list, &workers->idle_list);
- worker->idle = 1;
- workers->num_workers++;
- workers->num_workers_starting--;
- WARN_ON(workers->num_workers_starting < 0);
- spin_unlock_irq(&workers->lock);
-
- wake_up_process(worker->task);
- return 0;
-
-fail_kthread:
- kthread_stop(worker->task);
-fail:
- kfree(worker);
- spin_lock_irq(&workers->lock);
- workers->num_workers_starting--;
- spin_unlock_irq(&workers->lock);
- return ret;
-}
-
-int btrfs_start_workers(struct btrfs_workers *workers)
-{
- spin_lock_irq(&workers->lock);
- workers->num_workers_starting++;
- spin_unlock_irq(&workers->lock);
- return __btrfs_start_workers(workers);
-}
-
-/*
- * run through the list and find a worker thread that doesn't have a lot
- * to do right now. This can return null if we aren't yet at the thread
- * count limit and all of the threads are busy.
- */
-static struct btrfs_worker_thread *next_worker(struct btrfs_workers *workers)
-{
- struct btrfs_worker_thread *worker;
- struct list_head *next;
- int enforce_min;
-
- enforce_min = (workers->num_workers + workers->num_workers_starting) <
- workers->max_workers;
-
- /*
- * if we find an idle thread, don't move it to the end of the
- * idle list. This improves the chance that the next submission
- * will reuse the same thread, and maybe catch it while it is still
- * working
- */
- if (!list_empty(&workers->idle_list)) {
- next = workers->idle_list.next;
- worker = list_entry(next, struct btrfs_worker_thread,
- worker_list);
- return worker;
- }
- if (enforce_min || list_empty(&workers->worker_list))
- return NULL;
-
- /*
- * if we pick a busy task, move the task to the end of the list.
- * hopefully this will keep things somewhat evenly balanced.
- * Do the move in batches based on the sequence number. This groups
- * requests submitted at roughly the same time onto the same worker.
- */
- next = workers->worker_list.next;
- worker = list_entry(next, struct btrfs_worker_thread, worker_list);
- worker->sequence++;
-
- if (worker->sequence % workers->idle_thresh == 0)
- list_move_tail(next, &workers->worker_list);
- return worker;
-}
-
-/*
- * selects a worker thread to take the next job. This will either find
- * an idle worker, start a new worker up to the max count, or just return
- * one of the existing busy workers.
- */
-static struct btrfs_worker_thread *find_worker(struct btrfs_workers *workers)
-{
- struct btrfs_worker_thread *worker;
- unsigned long flags;
- struct list_head *fallback;
- int ret;
-
- spin_lock_irqsave(&workers->lock, flags);
-again:
- worker = next_worker(workers);
-
- if (!worker) {
- if (workers->num_workers + workers->num_workers_starting >=
- workers->max_workers) {
- goto fallback;
- } else if (workers->atomic_worker_start) {
- workers->atomic_start_pending = 1;
- goto fallback;
- } else {
- workers->num_workers_starting++;
- spin_unlock_irqrestore(&workers->lock, flags);
- /* we're below the limit, start another worker */
- ret = __btrfs_start_workers(workers);
- spin_lock_irqsave(&workers->lock, flags);
- if (ret)
- goto fallback;
- goto again;
- }
- }
- goto found;
-
-fallback:
- fallback = NULL;
- /*
- * we have failed to find any workers, just
- * return the first one we can find.
- */
- if (!list_empty(&workers->worker_list))
- fallback = workers->worker_list.next;
- if (!list_empty(&workers->idle_list))
- fallback = workers->idle_list.next;
- BUG_ON(!fallback);
- worker = list_entry(fallback,
- struct btrfs_worker_thread, worker_list);
-found:
- /*
- * this makes sure the worker doesn't exit before it is placed
- * onto a busy/idle list
- */
- atomic_inc(&worker->num_pending);
- spin_unlock_irqrestore(&workers->lock, flags);
- return worker;
-}
-
-/*
- * btrfs_requeue_work just puts the work item back on the tail of the list
- * it was taken from. It is intended for use with long running work functions
- * that make some progress and want to give the cpu up for others.
- */
-void btrfs_requeue_work(struct btrfs_work *work)
-{
- struct btrfs_worker_thread *worker = work->worker;
- unsigned long flags;
- int wake = 0;
-
- if (test_and_set_bit(WORK_QUEUED_BIT, &work->flags))
- return;
-
- spin_lock_irqsave(&worker->lock, flags);
- if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags))
- list_add_tail(&work->list, &worker->prio_pending);
- else
- list_add_tail(&work->list, &worker->pending);
- atomic_inc(&worker->num_pending);
-
- /* by definition we're busy, take ourselves off the idle
- * list
- */
- if (worker->idle) {
- spin_lock(&worker->workers->lock);
- worker->idle = 0;
- list_move_tail(&worker->worker_list,
- &worker->workers->worker_list);
- spin_unlock(&worker->workers->lock);
- }
- if (!worker->working) {
- wake = 1;
- worker->working = 1;
- }
-
- if (wake)
- wake_up_process(worker->task);
- spin_unlock_irqrestore(&worker->lock, flags);
-}
-
-void btrfs_set_work_high_prio(struct btrfs_work *work)
-{
- set_bit(WORK_HIGH_PRIO_BIT, &work->flags);
-}
-
-/*
- * places a struct btrfs_work into the pending queue of one of the kthreads
- */
-void btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work)
-{
- struct btrfs_worker_thread *worker;
- unsigned long flags;
- int wake = 0;
-
- /* don't requeue something already on a list */
- if (test_and_set_bit(WORK_QUEUED_BIT, &work->flags))
- return;
-
- worker = find_worker(workers);
- if (workers->ordered) {
- /*
- * you're not allowed to do ordered queues from an
- * interrupt handler
- */
- spin_lock(&workers->order_lock);
- if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags)) {
- list_add_tail(&work->order_list,
- &workers->prio_order_list);
- } else {
- list_add_tail(&work->order_list, &workers->order_list);
- }
- spin_unlock(&workers->order_lock);
- } else {
- INIT_LIST_HEAD(&work->order_list);
- }
-
- spin_lock_irqsave(&worker->lock, flags);
-
- if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags))
- list_add_tail(&work->list, &worker->prio_pending);
- else
- list_add_tail(&work->list, &worker->pending);
- check_busy_worker(worker);
-
- /*
- * avoid calling into wake_up_process if this thread has already
- * been kicked
- */
- if (!worker->working)
- wake = 1;
- worker->working = 1;
-
- if (wake)
- wake_up_process(worker->task);
- spin_unlock_irqrestore(&worker->lock, flags);
-}
-
struct __btrfs_workqueue_struct {
struct workqueue_struct *normal_wq;
/* List head pointing to ordered work list */
projects / karo-tx-linux.git / commitdiff