| 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/slab.h> |
| 21 | #include <linux/list.h> |
| 22 | #include <linux/spinlock.h> |
| 23 | #include <linux/freezer.h> |
| 24 | #include "async-thread.h" |
| 25 | |
| 26 | #define WORK_QUEUED_BIT 0 |
| 27 | #define WORK_DONE_BIT 1 |
| 28 | #define WORK_ORDER_DONE_BIT 2 |
| 29 | #define WORK_HIGH_PRIO_BIT 3 |
| 30 | |
| 31 | /* |
| 32 | * container for the kthread task pointer and the list of pending work |
| 33 | * One of these is allocated per thread. |
| 34 | */ |
| 35 | struct btrfs_worker_thread { |
| 36 | /* pool we belong to */ |
| 37 | struct btrfs_workers *workers; |
| 38 | |
| 39 | /* list of struct btrfs_work that are waiting for service */ |
| 40 | struct list_head pending; |
| 41 | struct list_head prio_pending; |
| 42 | |
| 43 | /* list of worker threads from struct btrfs_workers */ |
| 44 | struct list_head worker_list; |
| 45 | |
| 46 | /* kthread */ |
| 47 | struct task_struct *task; |
| 48 | |
| 49 | /* number of things on the pending list */ |
| 50 | atomic_t num_pending; |
| 51 | |
| 52 | /* reference counter for this struct */ |
| 53 | atomic_t refs; |
| 54 | |
| 55 | unsigned long sequence; |
| 56 | |
| 57 | /* protects the pending list. */ |
| 58 | spinlock_t lock; |
| 59 | |
| 60 | /* set to non-zero when this thread is already awake and kicking */ |
| 61 | int working; |
| 62 | |
| 63 | /* are we currently idle */ |
| 64 | int idle; |
| 65 | }; |
| 66 | |
| 67 | static int __btrfs_start_workers(struct btrfs_workers *workers); |
| 68 | |
| 69 | /* |
| 70 | * btrfs_start_workers uses kthread_run, which can block waiting for memory |
| 71 | * for a very long time. It will actually throttle on page writeback, |
| 72 | * and so it may not make progress until after our btrfs worker threads |
| 73 | * process all of the pending work structs in their queue |
| 74 | * |
| 75 | * This means we can't use btrfs_start_workers from inside a btrfs worker |
| 76 | * thread that is used as part of cleaning dirty memory, which pretty much |
| 77 | * involves all of the worker threads. |
| 78 | * |
| 79 | * Instead we have a helper queue who never has more than one thread |
| 80 | * where we scheduler thread start operations. This worker_start struct |
| 81 | * is used to contain the work and hold a pointer to the queue that needs |
| 82 | * another worker. |
| 83 | */ |
| 84 | struct worker_start { |
| 85 | struct btrfs_work work; |
| 86 | struct btrfs_workers *queue; |
| 87 | }; |
| 88 | |
| 89 | static void start_new_worker_func(struct btrfs_work *work) |
| 90 | { |
| 91 | struct worker_start *start; |
| 92 | start = container_of(work, struct worker_start, work); |
| 93 | __btrfs_start_workers(start->queue); |
| 94 | kfree(start); |
| 95 | } |
| 96 | |
| 97 | /* |
| 98 | * helper function to move a thread onto the idle list after it |
| 99 | * has finished some requests. |
| 100 | */ |
| 101 | static void check_idle_worker(struct btrfs_worker_thread *worker) |
| 102 | { |
| 103 | if (!worker->idle && atomic_read(&worker->num_pending) < |
| 104 | worker->workers->idle_thresh / 2) { |
| 105 | unsigned long flags; |
| 106 | spin_lock_irqsave(&worker->workers->lock, flags); |
| 107 | worker->idle = 1; |
| 108 | |
| 109 | /* the list may be empty if the worker is just starting */ |
| 110 | if (!list_empty(&worker->worker_list)) { |
| 111 | list_move(&worker->worker_list, |
| 112 | &worker->workers->idle_list); |
| 113 | } |
| 114 | spin_unlock_irqrestore(&worker->workers->lock, flags); |
| 115 | } |
| 116 | } |
| 117 | |
| 118 | /* |
| 119 | * helper function to move a thread off the idle list after new |
| 120 | * pending work is added. |
| 121 | */ |
| 122 | static void check_busy_worker(struct btrfs_worker_thread *worker) |
| 123 | { |
| 124 | if (worker->idle && atomic_read(&worker->num_pending) >= |
| 125 | worker->workers->idle_thresh) { |
| 126 | unsigned long flags; |
| 127 | spin_lock_irqsave(&worker->workers->lock, flags); |
| 128 | worker->idle = 0; |
| 129 | |
| 130 | if (!list_empty(&worker->worker_list)) { |
| 131 | list_move_tail(&worker->worker_list, |
| 132 | &worker->workers->worker_list); |
| 133 | } |
| 134 | spin_unlock_irqrestore(&worker->workers->lock, flags); |
| 135 | } |
| 136 | } |
| 137 | |
| 138 | static void check_pending_worker_creates(struct btrfs_worker_thread *worker) |
| 139 | { |
| 140 | struct btrfs_workers *workers = worker->workers; |
| 141 | struct worker_start *start; |
| 142 | unsigned long flags; |
| 143 | |
| 144 | rmb(); |
| 145 | if (!workers->atomic_start_pending) |
| 146 | return; |
| 147 | |
| 148 | start = kzalloc(sizeof(*start), GFP_NOFS); |
| 149 | if (!start) |
| 150 | return; |
| 151 | |
| 152 | start->work.func = start_new_worker_func; |
| 153 | start->queue = workers; |
| 154 | |
| 155 | spin_lock_irqsave(&workers->lock, flags); |
| 156 | if (!workers->atomic_start_pending) |
| 157 | goto out; |
| 158 | |
| 159 | workers->atomic_start_pending = 0; |
| 160 | if (workers->num_workers + workers->num_workers_starting >= |
| 161 | workers->max_workers) |
| 162 | goto out; |
| 163 | |
| 164 | workers->num_workers_starting += 1; |
| 165 | spin_unlock_irqrestore(&workers->lock, flags); |
| 166 | btrfs_queue_worker(workers->atomic_worker_start, &start->work); |
| 167 | return; |
| 168 | |
| 169 | out: |
| 170 | kfree(start); |
| 171 | spin_unlock_irqrestore(&workers->lock, flags); |
| 172 | } |
| 173 | |
| 174 | static noinline void run_ordered_completions(struct btrfs_workers *workers, |
| 175 | struct btrfs_work *work) |
| 176 | { |
| 177 | if (!workers->ordered) |
| 178 | return; |
| 179 | |
| 180 | set_bit(WORK_DONE_BIT, &work->flags); |
| 181 | |
| 182 | spin_lock(&workers->order_lock); |
| 183 | |
| 184 | while (1) { |
| 185 | if (!list_empty(&workers->prio_order_list)) { |
| 186 | work = list_entry(workers->prio_order_list.next, |
| 187 | struct btrfs_work, order_list); |
| 188 | } else if (!list_empty(&workers->order_list)) { |
| 189 | work = list_entry(workers->order_list.next, |
| 190 | struct btrfs_work, order_list); |
| 191 | } else { |
| 192 | break; |
| 193 | } |
| 194 | if (!test_bit(WORK_DONE_BIT, &work->flags)) |
| 195 | break; |
| 196 | |
| 197 | /* we are going to call the ordered done function, but |
| 198 | * we leave the work item on the list as a barrier so |
| 199 | * that later work items that are done don't have their |
| 200 | * functions called before this one returns |
| 201 | */ |
| 202 | if (test_and_set_bit(WORK_ORDER_DONE_BIT, &work->flags)) |
| 203 | break; |
| 204 | |
| 205 | spin_unlock(&workers->order_lock); |
| 206 | |
| 207 | work->ordered_func(work); |
| 208 | |
| 209 | /* now take the lock again and drop our item from the list */ |
| 210 | spin_lock(&workers->order_lock); |
| 211 | list_del(&work->order_list); |
| 212 | spin_unlock(&workers->order_lock); |
| 213 | |
| 214 | /* |
| 215 | * we don't want to call the ordered free functions |
| 216 | * with the lock held though |
| 217 | */ |
| 218 | work->ordered_free(work); |
| 219 | spin_lock(&workers->order_lock); |
| 220 | } |
| 221 | |
| 222 | spin_unlock(&workers->order_lock); |
| 223 | } |
| 224 | |
| 225 | static void put_worker(struct btrfs_worker_thread *worker) |
| 226 | { |
| 227 | if (atomic_dec_and_test(&worker->refs)) |
| 228 | kfree(worker); |
| 229 | } |
| 230 | |
| 231 | static int try_worker_shutdown(struct btrfs_worker_thread *worker) |
| 232 | { |
| 233 | int freeit = 0; |
| 234 | |
| 235 | spin_lock_irq(&worker->lock); |
| 236 | spin_lock(&worker->workers->lock); |
| 237 | if (worker->workers->num_workers > 1 && |
| 238 | worker->idle && |
| 239 | !worker->working && |
| 240 | !list_empty(&worker->worker_list) && |
| 241 | list_empty(&worker->prio_pending) && |
| 242 | list_empty(&worker->pending) && |
| 243 | atomic_read(&worker->num_pending) == 0) { |
| 244 | freeit = 1; |
| 245 | list_del_init(&worker->worker_list); |
| 246 | worker->workers->num_workers--; |
| 247 | } |
| 248 | spin_unlock(&worker->workers->lock); |
| 249 | spin_unlock_irq(&worker->lock); |
| 250 | |
| 251 | if (freeit) |
| 252 | put_worker(worker); |
| 253 | return freeit; |
| 254 | } |
| 255 | |
| 256 | static struct btrfs_work *get_next_work(struct btrfs_worker_thread *worker, |
| 257 | struct list_head *prio_head, |
| 258 | struct list_head *head) |
| 259 | { |
| 260 | struct btrfs_work *work = NULL; |
| 261 | struct list_head *cur = NULL; |
| 262 | |
| 263 | if(!list_empty(prio_head)) |
| 264 | cur = prio_head->next; |
| 265 | |
| 266 | smp_mb(); |
| 267 | if (!list_empty(&worker->prio_pending)) |
| 268 | goto refill; |
| 269 | |
| 270 | if (!list_empty(head)) |
| 271 | cur = head->next; |
| 272 | |
| 273 | if (cur) |
| 274 | goto out; |
| 275 | |
| 276 | refill: |
| 277 | spin_lock_irq(&worker->lock); |
| 278 | list_splice_tail_init(&worker->prio_pending, prio_head); |
| 279 | list_splice_tail_init(&worker->pending, head); |
| 280 | |
| 281 | if (!list_empty(prio_head)) |
| 282 | cur = prio_head->next; |
| 283 | else if (!list_empty(head)) |
| 284 | cur = head->next; |
| 285 | spin_unlock_irq(&worker->lock); |
| 286 | |
| 287 | if (!cur) |
| 288 | goto out_fail; |
| 289 | |
| 290 | out: |
| 291 | work = list_entry(cur, struct btrfs_work, list); |
| 292 | |
| 293 | out_fail: |
| 294 | return work; |
| 295 | } |
| 296 | |
| 297 | /* |
| 298 | * main loop for servicing work items |
| 299 | */ |
| 300 | static int worker_loop(void *arg) |
| 301 | { |
| 302 | struct btrfs_worker_thread *worker = arg; |
| 303 | struct list_head head; |
| 304 | struct list_head prio_head; |
| 305 | struct btrfs_work *work; |
| 306 | |
| 307 | INIT_LIST_HEAD(&head); |
| 308 | INIT_LIST_HEAD(&prio_head); |
| 309 | |
| 310 | set_freezable(); |
| 311 | |
| 312 | do { |
| 313 | again: |
| 314 | while (1) { |
| 315 | |
| 316 | |
| 317 | work = get_next_work(worker, &prio_head, &head); |
| 318 | if (!work) |
| 319 | break; |
| 320 | |
| 321 | list_del(&work->list); |
| 322 | clear_bit(WORK_QUEUED_BIT, &work->flags); |
| 323 | |
| 324 | work->worker = worker; |
| 325 | |
| 326 | work->func(work); |
| 327 | |
| 328 | atomic_dec(&worker->num_pending); |
| 329 | /* |
| 330 | * unless this is an ordered work queue, |
| 331 | * 'work' was probably freed by func above. |
| 332 | */ |
| 333 | run_ordered_completions(worker->workers, work); |
| 334 | |
| 335 | check_pending_worker_creates(worker); |
| 336 | cond_resched(); |
| 337 | } |
| 338 | |
| 339 | spin_lock_irq(&worker->lock); |
| 340 | check_idle_worker(worker); |
| 341 | |
| 342 | if (freezing(current)) { |
| 343 | worker->working = 0; |
| 344 | spin_unlock_irq(&worker->lock); |
| 345 | try_to_freeze(); |
| 346 | } else { |
| 347 | spin_unlock_irq(&worker->lock); |
| 348 | if (!kthread_freezable_should_stop(NULL)) { |
| 349 | cpu_relax(); |
| 350 | /* |
| 351 | * we've dropped the lock, did someone else |
| 352 | * jump_in? |
| 353 | */ |
| 354 | smp_mb(); |
| 355 | if (!list_empty(&worker->pending) || |
| 356 | !list_empty(&worker->prio_pending)) |
| 357 | continue; |
| 358 | |
| 359 | /* |
| 360 | * this short schedule allows more work to |
| 361 | * come in without the queue functions |
| 362 | * needing to go through wake_up_process() |
| 363 | * |
| 364 | * worker->working is still 1, so nobody |
| 365 | * is going to try and wake us up |
| 366 | */ |
| 367 | schedule_timeout(1); |
| 368 | smp_mb(); |
| 369 | if (!list_empty(&worker->pending) || |
| 370 | !list_empty(&worker->prio_pending)) |
| 371 | continue; |
| 372 | |
| 373 | if (kthread_freezable_should_stop(NULL)) |
| 374 | break; |
| 375 | |
| 376 | /* still no more work?, sleep for real */ |
| 377 | spin_lock_irq(&worker->lock); |
| 378 | set_current_state(TASK_INTERRUPTIBLE); |
| 379 | if (!list_empty(&worker->pending) || |
| 380 | !list_empty(&worker->prio_pending)) { |
| 381 | spin_unlock_irq(&worker->lock); |
| 382 | set_current_state(TASK_RUNNING); |
| 383 | goto again; |
| 384 | } |
| 385 | |
| 386 | /* |
| 387 | * this makes sure we get a wakeup when someone |
| 388 | * adds something new to the queue |
| 389 | */ |
| 390 | worker->working = 0; |
| 391 | spin_unlock_irq(&worker->lock); |
| 392 | |
| 393 | if (!kthread_freezable_should_stop(NULL)) { |
| 394 | schedule_timeout(HZ * 120); |
| 395 | if (!worker->working && |
| 396 | try_worker_shutdown(worker)) { |
| 397 | return 0; |
| 398 | } |
| 399 | } |
| 400 | } |
| 401 | __set_current_state(TASK_RUNNING); |
| 402 | } |
| 403 | } while (!kthread_freezable_should_stop(NULL)); |
| 404 | return 0; |
| 405 | } |
| 406 | |
| 407 | /* |
| 408 | * this will wait for all the worker threads to shutdown |
| 409 | */ |
| 410 | void btrfs_stop_workers(struct btrfs_workers *workers) |
| 411 | { |
| 412 | struct list_head *cur; |
| 413 | struct btrfs_worker_thread *worker; |
| 414 | int can_stop; |
| 415 | |
| 416 | spin_lock_irq(&workers->lock); |
| 417 | list_splice_init(&workers->idle_list, &workers->worker_list); |
| 418 | while (!list_empty(&workers->worker_list)) { |
| 419 | cur = workers->worker_list.next; |
| 420 | worker = list_entry(cur, struct btrfs_worker_thread, |
| 421 | worker_list); |
| 422 | |
| 423 | atomic_inc(&worker->refs); |
| 424 | workers->num_workers -= 1; |
| 425 | if (!list_empty(&worker->worker_list)) { |
| 426 | list_del_init(&worker->worker_list); |
| 427 | put_worker(worker); |
| 428 | can_stop = 1; |
| 429 | } else |
| 430 | can_stop = 0; |
| 431 | spin_unlock_irq(&workers->lock); |
| 432 | if (can_stop) |
| 433 | kthread_stop(worker->task); |
| 434 | spin_lock_irq(&workers->lock); |
| 435 | put_worker(worker); |
| 436 | } |
| 437 | spin_unlock_irq(&workers->lock); |
| 438 | } |
| 439 | |
| 440 | /* |
| 441 | * simple init on struct btrfs_workers |
| 442 | */ |
| 443 | void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max, |
| 444 | struct btrfs_workers *async_helper) |
| 445 | { |
| 446 | workers->num_workers = 0; |
| 447 | workers->num_workers_starting = 0; |
| 448 | INIT_LIST_HEAD(&workers->worker_list); |
| 449 | INIT_LIST_HEAD(&workers->idle_list); |
| 450 | INIT_LIST_HEAD(&workers->order_list); |
| 451 | INIT_LIST_HEAD(&workers->prio_order_list); |
| 452 | spin_lock_init(&workers->lock); |
| 453 | spin_lock_init(&workers->order_lock); |
| 454 | workers->max_workers = max; |
| 455 | workers->idle_thresh = 32; |
| 456 | workers->name = name; |
| 457 | workers->ordered = 0; |
| 458 | workers->atomic_start_pending = 0; |
| 459 | workers->atomic_worker_start = async_helper; |
| 460 | } |
| 461 | |
| 462 | /* |
| 463 | * starts new worker threads. This does not enforce the max worker |
| 464 | * count in case you need to temporarily go past it. |
| 465 | */ |
| 466 | static int __btrfs_start_workers(struct btrfs_workers *workers) |
| 467 | { |
| 468 | struct btrfs_worker_thread *worker; |
| 469 | int ret = 0; |
| 470 | |
| 471 | worker = kzalloc(sizeof(*worker), GFP_NOFS); |
| 472 | if (!worker) { |
| 473 | ret = -ENOMEM; |
| 474 | goto fail; |
| 475 | } |
| 476 | |
| 477 | INIT_LIST_HEAD(&worker->pending); |
| 478 | INIT_LIST_HEAD(&worker->prio_pending); |
| 479 | INIT_LIST_HEAD(&worker->worker_list); |
| 480 | spin_lock_init(&worker->lock); |
| 481 | |
| 482 | atomic_set(&worker->num_pending, 0); |
| 483 | atomic_set(&worker->refs, 1); |
| 484 | worker->workers = workers; |
| 485 | worker->task = kthread_run(worker_loop, worker, |
| 486 | "btrfs-%s-%d", workers->name, |
| 487 | workers->num_workers + 1); |
| 488 | if (IS_ERR(worker->task)) { |
| 489 | ret = PTR_ERR(worker->task); |
| 490 | kfree(worker); |
| 491 | goto fail; |
| 492 | } |
| 493 | spin_lock_irq(&workers->lock); |
| 494 | list_add_tail(&worker->worker_list, &workers->idle_list); |
| 495 | worker->idle = 1; |
| 496 | workers->num_workers++; |
| 497 | workers->num_workers_starting--; |
| 498 | WARN_ON(workers->num_workers_starting < 0); |
| 499 | spin_unlock_irq(&workers->lock); |
| 500 | |
| 501 | return 0; |
| 502 | fail: |
| 503 | spin_lock_irq(&workers->lock); |
| 504 | workers->num_workers_starting--; |
| 505 | spin_unlock_irq(&workers->lock); |
| 506 | return ret; |
| 507 | } |
| 508 | |
| 509 | int btrfs_start_workers(struct btrfs_workers *workers) |
| 510 | { |
| 511 | spin_lock_irq(&workers->lock); |
| 512 | workers->num_workers_starting++; |
| 513 | spin_unlock_irq(&workers->lock); |
| 514 | return __btrfs_start_workers(workers); |
| 515 | } |
| 516 | |
| 517 | /* |
| 518 | * run through the list and find a worker thread that doesn't have a lot |
| 519 | * to do right now. This can return null if we aren't yet at the thread |
| 520 | * count limit and all of the threads are busy. |
| 521 | */ |
| 522 | static struct btrfs_worker_thread *next_worker(struct btrfs_workers *workers) |
| 523 | { |
| 524 | struct btrfs_worker_thread *worker; |
| 525 | struct list_head *next; |
| 526 | int enforce_min; |
| 527 | |
| 528 | enforce_min = (workers->num_workers + workers->num_workers_starting) < |
| 529 | workers->max_workers; |
| 530 | |
| 531 | /* |
| 532 | * if we find an idle thread, don't move it to the end of the |
| 533 | * idle list. This improves the chance that the next submission |
| 534 | * will reuse the same thread, and maybe catch it while it is still |
| 535 | * working |
| 536 | */ |
| 537 | if (!list_empty(&workers->idle_list)) { |
| 538 | next = workers->idle_list.next; |
| 539 | worker = list_entry(next, struct btrfs_worker_thread, |
| 540 | worker_list); |
| 541 | return worker; |
| 542 | } |
| 543 | if (enforce_min || list_empty(&workers->worker_list)) |
| 544 | return NULL; |
| 545 | |
| 546 | /* |
| 547 | * if we pick a busy task, move the task to the end of the list. |
| 548 | * hopefully this will keep things somewhat evenly balanced. |
| 549 | * Do the move in batches based on the sequence number. This groups |
| 550 | * requests submitted at roughly the same time onto the same worker. |
| 551 | */ |
| 552 | next = workers->worker_list.next; |
| 553 | worker = list_entry(next, struct btrfs_worker_thread, worker_list); |
| 554 | worker->sequence++; |
| 555 | |
| 556 | if (worker->sequence % workers->idle_thresh == 0) |
| 557 | list_move_tail(next, &workers->worker_list); |
| 558 | return worker; |
| 559 | } |
| 560 | |
| 561 | /* |
| 562 | * selects a worker thread to take the next job. This will either find |
| 563 | * an idle worker, start a new worker up to the max count, or just return |
| 564 | * one of the existing busy workers. |
| 565 | */ |
| 566 | static struct btrfs_worker_thread *find_worker(struct btrfs_workers *workers) |
| 567 | { |
| 568 | struct btrfs_worker_thread *worker; |
| 569 | unsigned long flags; |
| 570 | struct list_head *fallback; |
| 571 | int ret; |
| 572 | |
| 573 | spin_lock_irqsave(&workers->lock, flags); |
| 574 | again: |
| 575 | worker = next_worker(workers); |
| 576 | |
| 577 | if (!worker) { |
| 578 | if (workers->num_workers + workers->num_workers_starting >= |
| 579 | workers->max_workers) { |
| 580 | goto fallback; |
| 581 | } else if (workers->atomic_worker_start) { |
| 582 | workers->atomic_start_pending = 1; |
| 583 | goto fallback; |
| 584 | } else { |
| 585 | workers->num_workers_starting++; |
| 586 | spin_unlock_irqrestore(&workers->lock, flags); |
| 587 | /* we're below the limit, start another worker */ |
| 588 | ret = __btrfs_start_workers(workers); |
| 589 | spin_lock_irqsave(&workers->lock, flags); |
| 590 | if (ret) |
| 591 | goto fallback; |
| 592 | goto again; |
| 593 | } |
| 594 | } |
| 595 | goto found; |
| 596 | |
| 597 | fallback: |
| 598 | fallback = NULL; |
| 599 | /* |
| 600 | * we have failed to find any workers, just |
| 601 | * return the first one we can find. |
| 602 | */ |
| 603 | if (!list_empty(&workers->worker_list)) |
| 604 | fallback = workers->worker_list.next; |
| 605 | if (!list_empty(&workers->idle_list)) |
| 606 | fallback = workers->idle_list.next; |
| 607 | BUG_ON(!fallback); |
| 608 | worker = list_entry(fallback, |
| 609 | struct btrfs_worker_thread, worker_list); |
| 610 | found: |
| 611 | /* |
| 612 | * this makes sure the worker doesn't exit before it is placed |
| 613 | * onto a busy/idle list |
| 614 | */ |
| 615 | atomic_inc(&worker->num_pending); |
| 616 | spin_unlock_irqrestore(&workers->lock, flags); |
| 617 | return worker; |
| 618 | } |
| 619 | |
| 620 | /* |
| 621 | * btrfs_requeue_work just puts the work item back on the tail of the list |
| 622 | * it was taken from. It is intended for use with long running work functions |
| 623 | * that make some progress and want to give the cpu up for others. |
| 624 | */ |
| 625 | void btrfs_requeue_work(struct btrfs_work *work) |
| 626 | { |
| 627 | struct btrfs_worker_thread *worker = work->worker; |
| 628 | unsigned long flags; |
| 629 | int wake = 0; |
| 630 | |
| 631 | if (test_and_set_bit(WORK_QUEUED_BIT, &work->flags)) |
| 632 | return; |
| 633 | |
| 634 | spin_lock_irqsave(&worker->lock, flags); |
| 635 | if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags)) |
| 636 | list_add_tail(&work->list, &worker->prio_pending); |
| 637 | else |
| 638 | list_add_tail(&work->list, &worker->pending); |
| 639 | atomic_inc(&worker->num_pending); |
| 640 | |
| 641 | /* by definition we're busy, take ourselves off the idle |
| 642 | * list |
| 643 | */ |
| 644 | if (worker->idle) { |
| 645 | spin_lock(&worker->workers->lock); |
| 646 | worker->idle = 0; |
| 647 | list_move_tail(&worker->worker_list, |
| 648 | &worker->workers->worker_list); |
| 649 | spin_unlock(&worker->workers->lock); |
| 650 | } |
| 651 | if (!worker->working) { |
| 652 | wake = 1; |
| 653 | worker->working = 1; |
| 654 | } |
| 655 | |
| 656 | if (wake) |
| 657 | wake_up_process(worker->task); |
| 658 | spin_unlock_irqrestore(&worker->lock, flags); |
| 659 | } |
| 660 | |
| 661 | void btrfs_set_work_high_prio(struct btrfs_work *work) |
| 662 | { |
| 663 | set_bit(WORK_HIGH_PRIO_BIT, &work->flags); |
| 664 | } |
| 665 | |
| 666 | /* |
| 667 | * places a struct btrfs_work into the pending queue of one of the kthreads |
| 668 | */ |
| 669 | void btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work) |
| 670 | { |
| 671 | struct btrfs_worker_thread *worker; |
| 672 | unsigned long flags; |
| 673 | int wake = 0; |
| 674 | |
| 675 | /* don't requeue something already on a list */ |
| 676 | if (test_and_set_bit(WORK_QUEUED_BIT, &work->flags)) |
| 677 | return; |
| 678 | |
| 679 | worker = find_worker(workers); |
| 680 | if (workers->ordered) { |
| 681 | /* |
| 682 | * you're not allowed to do ordered queues from an |
| 683 | * interrupt handler |
| 684 | */ |
| 685 | spin_lock(&workers->order_lock); |
| 686 | if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags)) { |
| 687 | list_add_tail(&work->order_list, |
| 688 | &workers->prio_order_list); |
| 689 | } else { |
| 690 | list_add_tail(&work->order_list, &workers->order_list); |
| 691 | } |
| 692 | spin_unlock(&workers->order_lock); |
| 693 | } else { |
| 694 | INIT_LIST_HEAD(&work->order_list); |
| 695 | } |
| 696 | |
| 697 | spin_lock_irqsave(&worker->lock, flags); |
| 698 | |
| 699 | if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags)) |
| 700 | list_add_tail(&work->list, &worker->prio_pending); |
| 701 | else |
| 702 | list_add_tail(&work->list, &worker->pending); |
| 703 | check_busy_worker(worker); |
| 704 | |
| 705 | /* |
| 706 | * avoid calling into wake_up_process if this thread has already |
| 707 | * been kicked |
| 708 | */ |
| 709 | if (!worker->working) |
| 710 | wake = 1; |
| 711 | worker->working = 1; |
| 712 | |
| 713 | if (wake) |
| 714 | wake_up_process(worker->task); |
| 715 | spin_unlock_irqrestore(&worker->lock, flags); |
| 716 | } |