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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 | ||
19 | #include <linux/kthread.h> | |
20 | #include <linux/list.h> | |
21 | #include <linux/spinlock.h> | |
b51912c9 | 22 | #include <linux/freezer.h> |
8b712842 CM |
23 | #include "async-thread.h" |
24 | ||
4a69a410 CM |
25 | #define WORK_QUEUED_BIT 0 |
26 | #define WORK_DONE_BIT 1 | |
27 | #define WORK_ORDER_DONE_BIT 2 | |
28 | ||
8b712842 CM |
29 | /* |
30 | * container for the kthread task pointer and the list of pending work | |
31 | * One of these is allocated per thread. | |
32 | */ | |
33 | struct btrfs_worker_thread { | |
35d8ba66 CM |
34 | /* pool we belong to */ |
35 | struct btrfs_workers *workers; | |
36 | ||
8b712842 CM |
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; | |
53863232 | 48 | |
4854ddd0 | 49 | unsigned long sequence; |
8b712842 CM |
50 | |
51 | /* protects the pending list. */ | |
52 | spinlock_t lock; | |
53 | ||
54 | /* set to non-zero when this thread is already awake and kicking */ | |
55 | int working; | |
35d8ba66 CM |
56 | |
57 | /* are we currently idle */ | |
58 | int idle; | |
8b712842 CM |
59 | }; |
60 | ||
35d8ba66 CM |
61 | /* |
62 | * helper function to move a thread onto the idle list after it | |
63 | * has finished some requests. | |
64 | */ | |
65 | static void check_idle_worker(struct btrfs_worker_thread *worker) | |
66 | { | |
67 | if (!worker->idle && atomic_read(&worker->num_pending) < | |
68 | worker->workers->idle_thresh / 2) { | |
69 | unsigned long flags; | |
70 | spin_lock_irqsave(&worker->workers->lock, flags); | |
71 | worker->idle = 1; | |
72 | list_move(&worker->worker_list, &worker->workers->idle_list); | |
73 | spin_unlock_irqrestore(&worker->workers->lock, flags); | |
74 | } | |
75 | } | |
76 | ||
77 | /* | |
78 | * helper function to move a thread off the idle list after new | |
79 | * pending work is added. | |
80 | */ | |
81 | static void check_busy_worker(struct btrfs_worker_thread *worker) | |
82 | { | |
83 | if (worker->idle && atomic_read(&worker->num_pending) >= | |
84 | worker->workers->idle_thresh) { | |
85 | unsigned long flags; | |
86 | spin_lock_irqsave(&worker->workers->lock, flags); | |
87 | worker->idle = 0; | |
88 | list_move_tail(&worker->worker_list, | |
89 | &worker->workers->worker_list); | |
90 | spin_unlock_irqrestore(&worker->workers->lock, flags); | |
91 | } | |
92 | } | |
93 | ||
4a69a410 CM |
94 | static noinline int run_ordered_completions(struct btrfs_workers *workers, |
95 | struct btrfs_work *work) | |
96 | { | |
97 | unsigned long flags; | |
98 | ||
99 | if (!workers->ordered) | |
100 | return 0; | |
101 | ||
102 | set_bit(WORK_DONE_BIT, &work->flags); | |
103 | ||
104 | spin_lock_irqsave(&workers->lock, flags); | |
105 | ||
d397712b | 106 | while (!list_empty(&workers->order_list)) { |
4a69a410 CM |
107 | work = list_entry(workers->order_list.next, |
108 | struct btrfs_work, order_list); | |
109 | ||
110 | if (!test_bit(WORK_DONE_BIT, &work->flags)) | |
111 | break; | |
112 | ||
113 | /* we are going to call the ordered done function, but | |
114 | * we leave the work item on the list as a barrier so | |
115 | * that later work items that are done don't have their | |
116 | * functions called before this one returns | |
117 | */ | |
118 | if (test_and_set_bit(WORK_ORDER_DONE_BIT, &work->flags)) | |
119 | break; | |
120 | ||
121 | spin_unlock_irqrestore(&workers->lock, flags); | |
122 | ||
123 | work->ordered_func(work); | |
124 | ||
125 | /* now take the lock again and call the freeing code */ | |
126 | spin_lock_irqsave(&workers->lock, flags); | |
127 | list_del(&work->order_list); | |
128 | work->ordered_free(work); | |
129 | } | |
130 | ||
131 | spin_unlock_irqrestore(&workers->lock, flags); | |
132 | return 0; | |
133 | } | |
134 | ||
8b712842 CM |
135 | /* |
136 | * main loop for servicing work items | |
137 | */ | |
138 | static int worker_loop(void *arg) | |
139 | { | |
140 | struct btrfs_worker_thread *worker = arg; | |
141 | struct list_head *cur; | |
142 | struct btrfs_work *work; | |
143 | do { | |
144 | spin_lock_irq(&worker->lock); | |
b51912c9 | 145 | again_locked: |
d397712b | 146 | while (!list_empty(&worker->pending)) { |
8b712842 CM |
147 | cur = worker->pending.next; |
148 | work = list_entry(cur, struct btrfs_work, list); | |
149 | list_del(&work->list); | |
4a69a410 | 150 | clear_bit(WORK_QUEUED_BIT, &work->flags); |
8b712842 CM |
151 | |
152 | work->worker = worker; | |
153 | spin_unlock_irq(&worker->lock); | |
154 | ||
155 | work->func(work); | |
156 | ||
157 | atomic_dec(&worker->num_pending); | |
4a69a410 CM |
158 | /* |
159 | * unless this is an ordered work queue, | |
160 | * 'work' was probably freed by func above. | |
161 | */ | |
162 | run_ordered_completions(worker->workers, work); | |
163 | ||
8b712842 | 164 | spin_lock_irq(&worker->lock); |
35d8ba66 | 165 | check_idle_worker(worker); |
4a69a410 | 166 | |
8b712842 | 167 | } |
8b712842 | 168 | if (freezing(current)) { |
b51912c9 CM |
169 | worker->working = 0; |
170 | spin_unlock_irq(&worker->lock); | |
8b712842 CM |
171 | refrigerator(); |
172 | } else { | |
8b712842 | 173 | spin_unlock_irq(&worker->lock); |
b51912c9 CM |
174 | if (!kthread_should_stop()) { |
175 | cpu_relax(); | |
176 | /* | |
177 | * we've dropped the lock, did someone else | |
178 | * jump_in? | |
179 | */ | |
180 | smp_mb(); | |
181 | if (!list_empty(&worker->pending)) | |
182 | continue; | |
183 | ||
184 | /* | |
185 | * this short schedule allows more work to | |
186 | * come in without the queue functions | |
187 | * needing to go through wake_up_process() | |
188 | * | |
189 | * worker->working is still 1, so nobody | |
190 | * is going to try and wake us up | |
191 | */ | |
192 | schedule_timeout(1); | |
193 | smp_mb(); | |
194 | if (!list_empty(&worker->pending)) | |
195 | continue; | |
196 | ||
b5555f77 AG |
197 | if (kthread_should_stop()) |
198 | break; | |
199 | ||
b51912c9 CM |
200 | /* still no more work?, sleep for real */ |
201 | spin_lock_irq(&worker->lock); | |
202 | set_current_state(TASK_INTERRUPTIBLE); | |
203 | if (!list_empty(&worker->pending)) | |
204 | goto again_locked; | |
205 | ||
206 | /* | |
207 | * this makes sure we get a wakeup when someone | |
208 | * adds something new to the queue | |
209 | */ | |
210 | worker->working = 0; | |
211 | spin_unlock_irq(&worker->lock); | |
212 | ||
b5555f77 AG |
213 | if (!kthread_should_stop()) |
214 | schedule(); | |
b51912c9 | 215 | } |
8b712842 CM |
216 | __set_current_state(TASK_RUNNING); |
217 | } | |
218 | } while (!kthread_should_stop()); | |
219 | return 0; | |
220 | } | |
221 | ||
222 | /* | |
223 | * this will wait for all the worker threads to shutdown | |
224 | */ | |
225 | int btrfs_stop_workers(struct btrfs_workers *workers) | |
226 | { | |
227 | struct list_head *cur; | |
228 | struct btrfs_worker_thread *worker; | |
229 | ||
35d8ba66 | 230 | list_splice_init(&workers->idle_list, &workers->worker_list); |
d397712b | 231 | while (!list_empty(&workers->worker_list)) { |
8b712842 CM |
232 | cur = workers->worker_list.next; |
233 | worker = list_entry(cur, struct btrfs_worker_thread, | |
234 | worker_list); | |
235 | kthread_stop(worker->task); | |
236 | list_del(&worker->worker_list); | |
237 | kfree(worker); | |
238 | } | |
239 | return 0; | |
240 | } | |
241 | ||
242 | /* | |
243 | * simple init on struct btrfs_workers | |
244 | */ | |
5443be45 | 245 | void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max) |
8b712842 CM |
246 | { |
247 | workers->num_workers = 0; | |
248 | INIT_LIST_HEAD(&workers->worker_list); | |
35d8ba66 | 249 | INIT_LIST_HEAD(&workers->idle_list); |
4a69a410 | 250 | INIT_LIST_HEAD(&workers->order_list); |
8b712842 CM |
251 | spin_lock_init(&workers->lock); |
252 | workers->max_workers = max; | |
61b49440 | 253 | workers->idle_thresh = 32; |
5443be45 | 254 | workers->name = name; |
4a69a410 | 255 | workers->ordered = 0; |
8b712842 CM |
256 | } |
257 | ||
258 | /* | |
259 | * starts new worker threads. This does not enforce the max worker | |
260 | * count in case you need to temporarily go past it. | |
261 | */ | |
262 | int btrfs_start_workers(struct btrfs_workers *workers, int num_workers) | |
263 | { | |
264 | struct btrfs_worker_thread *worker; | |
265 | int ret = 0; | |
266 | int i; | |
267 | ||
268 | for (i = 0; i < num_workers; i++) { | |
269 | worker = kzalloc(sizeof(*worker), GFP_NOFS); | |
270 | if (!worker) { | |
271 | ret = -ENOMEM; | |
272 | goto fail; | |
273 | } | |
274 | ||
275 | INIT_LIST_HEAD(&worker->pending); | |
276 | INIT_LIST_HEAD(&worker->worker_list); | |
277 | spin_lock_init(&worker->lock); | |
278 | atomic_set(&worker->num_pending, 0); | |
5443be45 CM |
279 | worker->task = kthread_run(worker_loop, worker, |
280 | "btrfs-%s-%d", workers->name, | |
281 | workers->num_workers + i); | |
35d8ba66 | 282 | worker->workers = workers; |
8b712842 | 283 | if (IS_ERR(worker->task)) { |
3bf10418 | 284 | kfree(worker); |
8b712842 CM |
285 | ret = PTR_ERR(worker->task); |
286 | goto fail; | |
287 | } | |
288 | ||
289 | spin_lock_irq(&workers->lock); | |
35d8ba66 | 290 | list_add_tail(&worker->worker_list, &workers->idle_list); |
4854ddd0 | 291 | worker->idle = 1; |
8b712842 CM |
292 | workers->num_workers++; |
293 | spin_unlock_irq(&workers->lock); | |
294 | } | |
295 | return 0; | |
296 | fail: | |
297 | btrfs_stop_workers(workers); | |
298 | return ret; | |
299 | } | |
300 | ||
301 | /* | |
302 | * run through the list and find a worker thread that doesn't have a lot | |
303 | * to do right now. This can return null if we aren't yet at the thread | |
304 | * count limit and all of the threads are busy. | |
305 | */ | |
306 | static struct btrfs_worker_thread *next_worker(struct btrfs_workers *workers) | |
307 | { | |
308 | struct btrfs_worker_thread *worker; | |
309 | struct list_head *next; | |
8b712842 CM |
310 | int enforce_min = workers->num_workers < workers->max_workers; |
311 | ||
8b712842 | 312 | /* |
35d8ba66 CM |
313 | * if we find an idle thread, don't move it to the end of the |
314 | * idle list. This improves the chance that the next submission | |
315 | * will reuse the same thread, and maybe catch it while it is still | |
316 | * working | |
8b712842 | 317 | */ |
35d8ba66 CM |
318 | if (!list_empty(&workers->idle_list)) { |
319 | next = workers->idle_list.next; | |
8b712842 CM |
320 | worker = list_entry(next, struct btrfs_worker_thread, |
321 | worker_list); | |
35d8ba66 | 322 | return worker; |
8b712842 | 323 | } |
35d8ba66 CM |
324 | if (enforce_min || list_empty(&workers->worker_list)) |
325 | return NULL; | |
326 | ||
8b712842 | 327 | /* |
35d8ba66 | 328 | * if we pick a busy task, move the task to the end of the list. |
d352ac68 CM |
329 | * hopefully this will keep things somewhat evenly balanced. |
330 | * Do the move in batches based on the sequence number. This groups | |
331 | * requests submitted at roughly the same time onto the same worker. | |
8b712842 | 332 | */ |
35d8ba66 CM |
333 | next = workers->worker_list.next; |
334 | worker = list_entry(next, struct btrfs_worker_thread, worker_list); | |
4854ddd0 CM |
335 | atomic_inc(&worker->num_pending); |
336 | worker->sequence++; | |
d352ac68 | 337 | |
53863232 | 338 | if (worker->sequence % workers->idle_thresh == 0) |
4854ddd0 | 339 | list_move_tail(next, &workers->worker_list); |
8b712842 CM |
340 | return worker; |
341 | } | |
342 | ||
d352ac68 CM |
343 | /* |
344 | * selects a worker thread to take the next job. This will either find | |
345 | * an idle worker, start a new worker up to the max count, or just return | |
346 | * one of the existing busy workers. | |
347 | */ | |
8b712842 CM |
348 | static struct btrfs_worker_thread *find_worker(struct btrfs_workers *workers) |
349 | { | |
350 | struct btrfs_worker_thread *worker; | |
351 | unsigned long flags; | |
352 | ||
353 | again: | |
354 | spin_lock_irqsave(&workers->lock, flags); | |
355 | worker = next_worker(workers); | |
356 | spin_unlock_irqrestore(&workers->lock, flags); | |
357 | ||
358 | if (!worker) { | |
359 | spin_lock_irqsave(&workers->lock, flags); | |
360 | if (workers->num_workers >= workers->max_workers) { | |
35d8ba66 | 361 | struct list_head *fallback = NULL; |
8b712842 CM |
362 | /* |
363 | * we have failed to find any workers, just | |
364 | * return the force one | |
365 | */ | |
35d8ba66 CM |
366 | if (!list_empty(&workers->worker_list)) |
367 | fallback = workers->worker_list.next; | |
368 | if (!list_empty(&workers->idle_list)) | |
369 | fallback = workers->idle_list.next; | |
370 | BUG_ON(!fallback); | |
371 | worker = list_entry(fallback, | |
8b712842 CM |
372 | struct btrfs_worker_thread, worker_list); |
373 | spin_unlock_irqrestore(&workers->lock, flags); | |
374 | } else { | |
375 | spin_unlock_irqrestore(&workers->lock, flags); | |
376 | /* we're below the limit, start another worker */ | |
377 | btrfs_start_workers(workers, 1); | |
378 | goto again; | |
379 | } | |
380 | } | |
381 | return worker; | |
382 | } | |
383 | ||
384 | /* | |
385 | * btrfs_requeue_work just puts the work item back on the tail of the list | |
386 | * it was taken from. It is intended for use with long running work functions | |
387 | * that make some progress and want to give the cpu up for others. | |
388 | */ | |
389 | int btrfs_requeue_work(struct btrfs_work *work) | |
390 | { | |
391 | struct btrfs_worker_thread *worker = work->worker; | |
392 | unsigned long flags; | |
a6837051 | 393 | int wake = 0; |
8b712842 | 394 | |
4a69a410 | 395 | if (test_and_set_bit(WORK_QUEUED_BIT, &work->flags)) |
8b712842 CM |
396 | goto out; |
397 | ||
398 | spin_lock_irqsave(&worker->lock, flags); | |
8b712842 | 399 | list_add_tail(&work->list, &worker->pending); |
b51912c9 | 400 | atomic_inc(&worker->num_pending); |
75ccf47d CM |
401 | |
402 | /* by definition we're busy, take ourselves off the idle | |
403 | * list | |
404 | */ | |
405 | if (worker->idle) { | |
406 | spin_lock_irqsave(&worker->workers->lock, flags); | |
407 | worker->idle = 0; | |
408 | list_move_tail(&worker->worker_list, | |
409 | &worker->workers->worker_list); | |
410 | spin_unlock_irqrestore(&worker->workers->lock, flags); | |
411 | } | |
a6837051 CM |
412 | if (!worker->working) { |
413 | wake = 1; | |
414 | worker->working = 1; | |
415 | } | |
75ccf47d | 416 | |
8b712842 | 417 | spin_unlock_irqrestore(&worker->lock, flags); |
a6837051 CM |
418 | if (wake) |
419 | wake_up_process(worker->task); | |
8b712842 | 420 | out: |
a6837051 | 421 | |
8b712842 CM |
422 | return 0; |
423 | } | |
424 | ||
425 | /* | |
426 | * places a struct btrfs_work into the pending queue of one of the kthreads | |
427 | */ | |
428 | int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work) | |
429 | { | |
430 | struct btrfs_worker_thread *worker; | |
431 | unsigned long flags; | |
432 | int wake = 0; | |
433 | ||
434 | /* don't requeue something already on a list */ | |
4a69a410 | 435 | if (test_and_set_bit(WORK_QUEUED_BIT, &work->flags)) |
8b712842 CM |
436 | goto out; |
437 | ||
438 | worker = find_worker(workers); | |
4a69a410 CM |
439 | if (workers->ordered) { |
440 | spin_lock_irqsave(&workers->lock, flags); | |
441 | list_add_tail(&work->order_list, &workers->order_list); | |
442 | spin_unlock_irqrestore(&workers->lock, flags); | |
443 | } else { | |
444 | INIT_LIST_HEAD(&work->order_list); | |
445 | } | |
8b712842 CM |
446 | |
447 | spin_lock_irqsave(&worker->lock, flags); | |
a6837051 | 448 | |
b51912c9 | 449 | list_add_tail(&work->list, &worker->pending); |
8b712842 | 450 | atomic_inc(&worker->num_pending); |
35d8ba66 | 451 | check_busy_worker(worker); |
8b712842 CM |
452 | |
453 | /* | |
454 | * avoid calling into wake_up_process if this thread has already | |
455 | * been kicked | |
456 | */ | |
457 | if (!worker->working) | |
458 | wake = 1; | |
459 | worker->working = 1; | |
460 | ||
461 | spin_unlock_irqrestore(&worker->lock, flags); | |
462 | ||
463 | if (wake) | |
464 | wake_up_process(worker->task); | |
465 | out: | |
466 | return 0; | |
467 | } |