e55b689268
Added thread pool exit condition into the thread_pool_del_worker(). If called in parallel another thread can steal Signed-off-by: Evgeniy Polyakov <zbr@ioremap.net> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
346 lines
7.5 KiB
C
346 lines
7.5 KiB
C
/*
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* 2007+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net>
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* All rights reserved.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*/
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#include <linux/kernel.h>
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#include <linux/dst.h>
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#include <linux/kthread.h>
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#include <linux/slab.h>
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/*
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* Thread pool abstraction allows to schedule a work to be performed
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* on behalf of kernel thread. One does not operate with threads itself,
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* instead user provides setup and cleanup callbacks for thread pool itself,
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* and action and cleanup callbacks for each submitted work.
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*
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* Each worker has private data initialized at creation time and data,
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* provided by user at scheduling time.
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*
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* When action is being performed, thread can not be used by other users,
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* instead they will sleep until there is free thread to pick their work.
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*/
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struct thread_pool_worker
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{
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struct list_head worker_entry;
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struct task_struct *thread;
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struct thread_pool *pool;
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int error;
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int has_data;
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int need_exit;
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unsigned int id;
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wait_queue_head_t wait;
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void *private;
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void *schedule_data;
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int (* action)(void *private, void *schedule_data);
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void (* cleanup)(void *private);
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};
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static void thread_pool_exit_worker(struct thread_pool_worker *w)
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{
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kthread_stop(w->thread);
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w->cleanup(w->private);
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kfree(w);
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}
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/*
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* Called to mark thread as ready and allow users to schedule new work.
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*/
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static void thread_pool_worker_make_ready(struct thread_pool_worker *w)
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{
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struct thread_pool *p = w->pool;
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mutex_lock(&p->thread_lock);
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if (!w->need_exit) {
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list_move_tail(&w->worker_entry, &p->ready_list);
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w->has_data = 0;
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mutex_unlock(&p->thread_lock);
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wake_up(&p->wait);
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} else {
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p->thread_num--;
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list_del(&w->worker_entry);
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mutex_unlock(&p->thread_lock);
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thread_pool_exit_worker(w);
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}
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}
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/*
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* Thread action loop: waits until there is new work.
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*/
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static int thread_pool_worker_func(void *data)
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{
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struct thread_pool_worker *w = data;
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while (!kthread_should_stop()) {
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wait_event_interruptible(w->wait,
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kthread_should_stop() || w->has_data);
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if (kthread_should_stop())
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break;
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if (!w->has_data)
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continue;
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w->action(w->private, w->schedule_data);
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thread_pool_worker_make_ready(w);
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}
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return 0;
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}
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/*
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* Remove single worker without specifying which one.
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*/
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void thread_pool_del_worker(struct thread_pool *p)
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{
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struct thread_pool_worker *w = NULL;
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while (!w && p->thread_num) {
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wait_event(p->wait, !list_empty(&p->ready_list) || !p->thread_num);
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dprintk("%s: locking list_empty: %d, thread_num: %d.\n",
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__func__, list_empty(&p->ready_list), p->thread_num);
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mutex_lock(&p->thread_lock);
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if (!list_empty(&p->ready_list)) {
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w = list_first_entry(&p->ready_list,
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struct thread_pool_worker,
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worker_entry);
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dprintk("%s: deleting w: %p, thread_num: %d, list: %p [%p.%p].\n",
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__func__, w, p->thread_num, &p->ready_list,
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p->ready_list.prev, p->ready_list.next);
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p->thread_num--;
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list_del(&w->worker_entry);
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}
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mutex_unlock(&p->thread_lock);
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}
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if (w)
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thread_pool_exit_worker(w);
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dprintk("%s: deleted w: %p, thread_num: %d.\n",
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__func__, w, p->thread_num);
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}
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/*
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* Remove a worker with given ID.
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*/
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void thread_pool_del_worker_id(struct thread_pool *p, unsigned int id)
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{
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struct thread_pool_worker *w;
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int found = 0;
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mutex_lock(&p->thread_lock);
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list_for_each_entry(w, &p->ready_list, worker_entry) {
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if (w->id == id) {
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found = 1;
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p->thread_num--;
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list_del(&w->worker_entry);
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break;
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}
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}
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if (!found) {
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list_for_each_entry(w, &p->active_list, worker_entry) {
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if (w->id == id) {
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w->need_exit = 1;
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break;
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}
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}
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}
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mutex_unlock(&p->thread_lock);
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if (found)
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thread_pool_exit_worker(w);
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}
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/*
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* Add new worker thread with given parameters.
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* If initialization callback fails, return error.
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*/
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int thread_pool_add_worker(struct thread_pool *p,
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char *name,
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unsigned int id,
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void *(* init)(void *private),
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void (* cleanup)(void *private),
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void *private)
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{
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struct thread_pool_worker *w;
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int err = -ENOMEM;
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w = kzalloc(sizeof(struct thread_pool_worker), GFP_KERNEL);
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if (!w)
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goto err_out_exit;
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w->pool = p;
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init_waitqueue_head(&w->wait);
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w->cleanup = cleanup;
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w->id = id;
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w->thread = kthread_run(thread_pool_worker_func, w, "%s", name);
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if (IS_ERR(w->thread)) {
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err = PTR_ERR(w->thread);
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goto err_out_free;
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}
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w->private = init(private);
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if (IS_ERR(w->private)) {
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err = PTR_ERR(w->private);
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goto err_out_stop_thread;
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}
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mutex_lock(&p->thread_lock);
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list_add_tail(&w->worker_entry, &p->ready_list);
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p->thread_num++;
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mutex_unlock(&p->thread_lock);
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return 0;
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err_out_stop_thread:
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kthread_stop(w->thread);
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err_out_free:
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kfree(w);
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err_out_exit:
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return err;
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}
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/*
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* Destroy the whole pool.
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*/
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void thread_pool_destroy(struct thread_pool *p)
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{
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while (p->thread_num) {
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dprintk("%s: num: %d.\n", __func__, p->thread_num);
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thread_pool_del_worker(p);
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}
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kfree(p);
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}
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/*
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* Create a pool with given number of threads.
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* They will have sequential IDs started from zero.
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*/
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struct thread_pool *thread_pool_create(int num, char *name,
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void *(* init)(void *private),
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void (* cleanup)(void *private),
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void *private)
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{
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struct thread_pool_worker *w, *tmp;
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struct thread_pool *p;
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int err = -ENOMEM;
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int i;
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p = kzalloc(sizeof(struct thread_pool), GFP_KERNEL);
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if (!p)
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goto err_out_exit;
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init_waitqueue_head(&p->wait);
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mutex_init(&p->thread_lock);
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INIT_LIST_HEAD(&p->ready_list);
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INIT_LIST_HEAD(&p->active_list);
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p->thread_num = 0;
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for (i=0; i<num; ++i) {
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err = thread_pool_add_worker(p, name, i, init,
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cleanup, private);
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if (err)
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goto err_out_free_all;
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}
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return p;
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err_out_free_all:
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list_for_each_entry_safe(w, tmp, &p->ready_list, worker_entry) {
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list_del(&w->worker_entry);
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thread_pool_exit_worker(w);
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}
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kfree(p);
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err_out_exit:
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return ERR_PTR(err);
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}
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/*
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* Schedule execution of the action on a given thread,
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* provided ID pointer has to match previously stored
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* private data.
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*/
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int thread_pool_schedule_private(struct thread_pool *p,
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int (* setup)(void *private, void *data),
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int (* action)(void *private, void *data),
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void *data, long timeout, void *id)
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{
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struct thread_pool_worker *w, *tmp, *worker = NULL;
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int err = 0;
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while (!worker && !err) {
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timeout = wait_event_interruptible_timeout(p->wait,
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!list_empty(&p->ready_list),
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timeout);
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if (!timeout) {
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err = -ETIMEDOUT;
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break;
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}
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worker = NULL;
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mutex_lock(&p->thread_lock);
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list_for_each_entry_safe(w, tmp, &p->ready_list, worker_entry) {
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if (id && id != w->private)
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continue;
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worker = w;
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list_move_tail(&w->worker_entry, &p->active_list);
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err = setup(w->private, data);
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if (!err) {
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w->schedule_data = data;
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w->action = action;
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w->has_data = 1;
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wake_up(&w->wait);
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} else {
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list_move_tail(&w->worker_entry, &p->ready_list);
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}
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break;
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}
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mutex_unlock(&p->thread_lock);
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}
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return err;
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}
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/*
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* Schedule execution on arbitrary thread from the pool.
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*/
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int thread_pool_schedule(struct thread_pool *p,
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int (* setup)(void *private, void *data),
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int (* action)(void *private, void *data),
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void *data, long timeout)
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{
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return thread_pool_schedule_private(p, setup,
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action, data, timeout, NULL);
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}
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