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8b712842 CM |
1 | /* |
2 | * Copyright (C) 2007 Oracle. All rights reserved. | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU General Public | |
6 | * License v2 as published by the Free Software Foundation. | |
7 | * | |
8 | * This program is distributed in the hope that it will be useful, | |
9 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
11 | * General Public License for more details. | |
12 | * | |
13 | * You should have received a copy of the GNU General Public | |
14 | * License along with this program; if not, write to the | |
15 | * Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
16 | * Boston, MA 021110-1307, USA. | |
17 | */ | |
18 | ||
d05e5a4d | 19 | #include <linux/version.h> |
8b712842 CM |
20 | #include <linux/kthread.h> |
21 | #include <linux/list.h> | |
22 | #include <linux/spinlock.h> | |
d05e5a4d CM |
23 | |
24 | #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,20) | |
25 | # include <linux/freezer.h> | |
26 | #else | |
27 | # include <linux/sched.h> | |
28 | #endif | |
29 | ||
8b712842 CM |
30 | #include "async-thread.h" |
31 | ||
32 | /* | |
33 | * container for the kthread task pointer and the list of pending work | |
34 | * One of these is allocated per thread. | |
35 | */ | |
36 | struct btrfs_worker_thread { | |
37 | /* list of struct btrfs_work that are waiting for service */ | |
38 | struct list_head pending; | |
39 | ||
40 | /* list of worker threads from struct btrfs_workers */ | |
41 | struct list_head worker_list; | |
42 | ||
43 | /* kthread */ | |
44 | struct task_struct *task; | |
45 | ||
46 | /* number of things on the pending list */ | |
47 | atomic_t num_pending; | |
48 | ||
49 | /* protects the pending list. */ | |
50 | spinlock_t lock; | |
51 | ||
52 | /* set to non-zero when this thread is already awake and kicking */ | |
53 | int working; | |
54 | }; | |
55 | ||
56 | /* | |
57 | * main loop for servicing work items | |
58 | */ | |
59 | static int worker_loop(void *arg) | |
60 | { | |
61 | struct btrfs_worker_thread *worker = arg; | |
62 | struct list_head *cur; | |
63 | struct btrfs_work *work; | |
64 | do { | |
65 | spin_lock_irq(&worker->lock); | |
66 | while(!list_empty(&worker->pending)) { | |
67 | cur = worker->pending.next; | |
68 | work = list_entry(cur, struct btrfs_work, list); | |
69 | list_del(&work->list); | |
70 | clear_bit(0, &work->flags); | |
71 | ||
72 | work->worker = worker; | |
73 | spin_unlock_irq(&worker->lock); | |
74 | ||
75 | work->func(work); | |
76 | ||
77 | atomic_dec(&worker->num_pending); | |
78 | spin_lock_irq(&worker->lock); | |
79 | } | |
80 | worker->working = 0; | |
81 | if (freezing(current)) { | |
82 | refrigerator(); | |
83 | } else { | |
84 | set_current_state(TASK_INTERRUPTIBLE); | |
85 | spin_unlock_irq(&worker->lock); | |
86 | schedule(); | |
87 | __set_current_state(TASK_RUNNING); | |
88 | } | |
89 | } while (!kthread_should_stop()); | |
90 | return 0; | |
91 | } | |
92 | ||
93 | /* | |
94 | * this will wait for all the worker threads to shutdown | |
95 | */ | |
96 | int btrfs_stop_workers(struct btrfs_workers *workers) | |
97 | { | |
98 | struct list_head *cur; | |
99 | struct btrfs_worker_thread *worker; | |
100 | ||
101 | while(!list_empty(&workers->worker_list)) { | |
102 | cur = workers->worker_list.next; | |
103 | worker = list_entry(cur, struct btrfs_worker_thread, | |
104 | worker_list); | |
105 | kthread_stop(worker->task); | |
106 | list_del(&worker->worker_list); | |
107 | kfree(worker); | |
108 | } | |
109 | return 0; | |
110 | } | |
111 | ||
112 | /* | |
113 | * simple init on struct btrfs_workers | |
114 | */ | |
115 | void btrfs_init_workers(struct btrfs_workers *workers, int max) | |
116 | { | |
117 | workers->num_workers = 0; | |
118 | INIT_LIST_HEAD(&workers->worker_list); | |
119 | workers->last = NULL; | |
120 | spin_lock_init(&workers->lock); | |
121 | workers->max_workers = max; | |
122 | } | |
123 | ||
124 | /* | |
125 | * starts new worker threads. This does not enforce the max worker | |
126 | * count in case you need to temporarily go past it. | |
127 | */ | |
128 | int btrfs_start_workers(struct btrfs_workers *workers, int num_workers) | |
129 | { | |
130 | struct btrfs_worker_thread *worker; | |
131 | int ret = 0; | |
132 | int i; | |
133 | ||
134 | for (i = 0; i < num_workers; i++) { | |
135 | worker = kzalloc(sizeof(*worker), GFP_NOFS); | |
136 | if (!worker) { | |
137 | ret = -ENOMEM; | |
138 | goto fail; | |
139 | } | |
140 | ||
141 | INIT_LIST_HEAD(&worker->pending); | |
142 | INIT_LIST_HEAD(&worker->worker_list); | |
143 | spin_lock_init(&worker->lock); | |
144 | atomic_set(&worker->num_pending, 0); | |
145 | worker->task = kthread_run(worker_loop, worker, "btrfs"); | |
146 | if (IS_ERR(worker->task)) { | |
147 | ret = PTR_ERR(worker->task); | |
148 | goto fail; | |
149 | } | |
150 | ||
151 | spin_lock_irq(&workers->lock); | |
152 | list_add_tail(&worker->worker_list, &workers->worker_list); | |
153 | workers->last = worker; | |
154 | workers->num_workers++; | |
155 | spin_unlock_irq(&workers->lock); | |
156 | } | |
157 | return 0; | |
158 | fail: | |
159 | btrfs_stop_workers(workers); | |
160 | return ret; | |
161 | } | |
162 | ||
163 | /* | |
164 | * run through the list and find a worker thread that doesn't have a lot | |
165 | * to do right now. This can return null if we aren't yet at the thread | |
166 | * count limit and all of the threads are busy. | |
167 | */ | |
168 | static struct btrfs_worker_thread *next_worker(struct btrfs_workers *workers) | |
169 | { | |
170 | struct btrfs_worker_thread *worker; | |
171 | struct list_head *next; | |
172 | struct list_head *start; | |
173 | int enforce_min = workers->num_workers < workers->max_workers; | |
174 | ||
175 | /* start with the last thread if it isn't busy */ | |
176 | worker = workers->last; | |
177 | if (atomic_read(&worker->num_pending) < 64) | |
178 | goto done; | |
179 | ||
180 | next = worker->worker_list.next; | |
181 | start = &worker->worker_list; | |
182 | ||
183 | /* | |
184 | * check all the workers for someone that is bored. FIXME, do | |
185 | * something smart here | |
186 | */ | |
187 | while(next != start) { | |
188 | if (next == &workers->worker_list) { | |
189 | next = workers->worker_list.next; | |
190 | continue; | |
191 | } | |
192 | worker = list_entry(next, struct btrfs_worker_thread, | |
193 | worker_list); | |
194 | if (atomic_read(&worker->num_pending) < 64 || !enforce_min) | |
195 | goto done; | |
196 | next = next->next; | |
197 | } | |
198 | /* | |
199 | * nobody was bored, if we're already at the max thread count, | |
200 | * use the last thread | |
201 | */ | |
202 | if (!enforce_min || atomic_read(&workers->last->num_pending) < 64) { | |
203 | return workers->last; | |
204 | } | |
205 | return NULL; | |
206 | done: | |
207 | workers->last = worker; | |
208 | return worker; | |
209 | } | |
210 | ||
211 | static struct btrfs_worker_thread *find_worker(struct btrfs_workers *workers) | |
212 | { | |
213 | struct btrfs_worker_thread *worker; | |
214 | unsigned long flags; | |
215 | ||
216 | again: | |
217 | spin_lock_irqsave(&workers->lock, flags); | |
218 | worker = next_worker(workers); | |
219 | spin_unlock_irqrestore(&workers->lock, flags); | |
220 | ||
221 | if (!worker) { | |
222 | spin_lock_irqsave(&workers->lock, flags); | |
223 | if (workers->num_workers >= workers->max_workers) { | |
224 | /* | |
225 | * we have failed to find any workers, just | |
226 | * return the force one | |
227 | */ | |
228 | worker = list_entry(workers->worker_list.next, | |
229 | struct btrfs_worker_thread, worker_list); | |
230 | spin_unlock_irqrestore(&workers->lock, flags); | |
231 | } else { | |
232 | spin_unlock_irqrestore(&workers->lock, flags); | |
233 | /* we're below the limit, start another worker */ | |
234 | btrfs_start_workers(workers, 1); | |
235 | goto again; | |
236 | } | |
237 | } | |
238 | return worker; | |
239 | } | |
240 | ||
241 | /* | |
242 | * btrfs_requeue_work just puts the work item back on the tail of the list | |
243 | * it was taken from. It is intended for use with long running work functions | |
244 | * that make some progress and want to give the cpu up for others. | |
245 | */ | |
246 | int btrfs_requeue_work(struct btrfs_work *work) | |
247 | { | |
248 | struct btrfs_worker_thread *worker = work->worker; | |
249 | unsigned long flags; | |
250 | ||
251 | if (test_and_set_bit(0, &work->flags)) | |
252 | goto out; | |
253 | ||
254 | spin_lock_irqsave(&worker->lock, flags); | |
255 | atomic_inc(&worker->num_pending); | |
256 | list_add_tail(&work->list, &worker->pending); | |
257 | spin_unlock_irqrestore(&worker->lock, flags); | |
258 | out: | |
259 | return 0; | |
260 | } | |
261 | ||
262 | /* | |
263 | * places a struct btrfs_work into the pending queue of one of the kthreads | |
264 | */ | |
265 | int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work) | |
266 | { | |
267 | struct btrfs_worker_thread *worker; | |
268 | unsigned long flags; | |
269 | int wake = 0; | |
270 | ||
271 | /* don't requeue something already on a list */ | |
272 | if (test_and_set_bit(0, &work->flags)) | |
273 | goto out; | |
274 | ||
275 | worker = find_worker(workers); | |
276 | ||
277 | spin_lock_irqsave(&worker->lock, flags); | |
278 | atomic_inc(&worker->num_pending); | |
279 | list_add_tail(&work->list, &worker->pending); | |
280 | ||
281 | /* | |
282 | * avoid calling into wake_up_process if this thread has already | |
283 | * been kicked | |
284 | */ | |
285 | if (!worker->working) | |
286 | wake = 1; | |
287 | worker->working = 1; | |
288 | ||
289 | spin_unlock_irqrestore(&worker->lock, flags); | |
290 | ||
291 | if (wake) | |
292 | wake_up_process(worker->task); | |
293 | out: | |
294 | return 0; | |
295 | } |