]>
Commit | Line | Data |
---|---|---|
1 | /* | |
2 | * kernel/workqueue.c - generic async execution with shared worker pool | |
3 | * | |
4 | * Copyright (C) 2002 Ingo Molnar | |
5 | * | |
6 | * Derived from the taskqueue/keventd code by: | |
7 | * David Woodhouse <dwmw2@infradead.org> | |
8 | * Andrew Morton | |
9 | * Kai Petzke <wpp@marie.physik.tu-berlin.de> | |
10 | * Theodore Ts'o <tytso@mit.edu> | |
11 | * | |
12 | * Made to use alloc_percpu by Christoph Lameter. | |
13 | * | |
14 | * Copyright (C) 2010 SUSE Linux Products GmbH | |
15 | * Copyright (C) 2010 Tejun Heo <tj@kernel.org> | |
16 | * | |
17 | * This is the generic async execution mechanism. Work items as are | |
18 | * executed in process context. The worker pool is shared and | |
19 | * automatically managed. There is one worker pool for each CPU and | |
20 | * one extra for works which are better served by workers which are | |
21 | * not bound to any specific CPU. | |
22 | * | |
23 | * Please read Documentation/workqueue.txt for details. | |
24 | */ | |
25 | ||
26 | #include <linux/export.h> | |
27 | #include <linux/kernel.h> | |
28 | #include <linux/sched.h> | |
29 | #include <linux/init.h> | |
30 | #include <linux/signal.h> | |
31 | #include <linux/completion.h> | |
32 | #include <linux/workqueue.h> | |
33 | #include <linux/slab.h> | |
34 | #include <linux/cpu.h> | |
35 | #include <linux/notifier.h> | |
36 | #include <linux/kthread.h> | |
37 | #include <linux/hardirq.h> | |
38 | #include <linux/mempolicy.h> | |
39 | #include <linux/freezer.h> | |
40 | #include <linux/kallsyms.h> | |
41 | #include <linux/debug_locks.h> | |
42 | #include <linux/lockdep.h> | |
43 | #include <linux/idr.h> | |
44 | ||
45 | #include "workqueue_sched.h" | |
46 | ||
47 | enum { | |
48 | /* | |
49 | * global_cwq flags | |
50 | * | |
51 | * A bound gcwq is either associated or disassociated with its CPU. | |
52 | * While associated (!DISASSOCIATED), all workers are bound to the | |
53 | * CPU and none has %WORKER_UNBOUND set and concurrency management | |
54 | * is in effect. | |
55 | * | |
56 | * While DISASSOCIATED, the cpu may be offline and all workers have | |
57 | * %WORKER_UNBOUND set and concurrency management disabled, and may | |
58 | * be executing on any CPU. The gcwq behaves as an unbound one. | |
59 | * | |
60 | * Note that DISASSOCIATED can be flipped only while holding | |
61 | * managership of all pools on the gcwq to avoid changing binding | |
62 | * state while create_worker() is in progress. | |
63 | */ | |
64 | GCWQ_DISASSOCIATED = 1 << 0, /* cpu can't serve workers */ | |
65 | GCWQ_FREEZING = 1 << 1, /* freeze in progress */ | |
66 | ||
67 | /* pool flags */ | |
68 | POOL_MANAGE_WORKERS = 1 << 0, /* need to manage workers */ | |
69 | ||
70 | /* worker flags */ | |
71 | WORKER_STARTED = 1 << 0, /* started */ | |
72 | WORKER_DIE = 1 << 1, /* die die die */ | |
73 | WORKER_IDLE = 1 << 2, /* is idle */ | |
74 | WORKER_PREP = 1 << 3, /* preparing to run works */ | |
75 | WORKER_REBIND = 1 << 5, /* mom is home, come back */ | |
76 | WORKER_CPU_INTENSIVE = 1 << 6, /* cpu intensive */ | |
77 | WORKER_UNBOUND = 1 << 7, /* worker is unbound */ | |
78 | ||
79 | WORKER_NOT_RUNNING = WORKER_PREP | WORKER_REBIND | WORKER_UNBOUND | | |
80 | WORKER_CPU_INTENSIVE, | |
81 | ||
82 | NR_WORKER_POOLS = 2, /* # worker pools per gcwq */ | |
83 | ||
84 | BUSY_WORKER_HASH_ORDER = 6, /* 64 pointers */ | |
85 | BUSY_WORKER_HASH_SIZE = 1 << BUSY_WORKER_HASH_ORDER, | |
86 | BUSY_WORKER_HASH_MASK = BUSY_WORKER_HASH_SIZE - 1, | |
87 | ||
88 | MAX_IDLE_WORKERS_RATIO = 4, /* 1/4 of busy can be idle */ | |
89 | IDLE_WORKER_TIMEOUT = 300 * HZ, /* keep idle ones for 5 mins */ | |
90 | ||
91 | MAYDAY_INITIAL_TIMEOUT = HZ / 100 >= 2 ? HZ / 100 : 2, | |
92 | /* call for help after 10ms | |
93 | (min two ticks) */ | |
94 | MAYDAY_INTERVAL = HZ / 10, /* and then every 100ms */ | |
95 | CREATE_COOLDOWN = HZ, /* time to breath after fail */ | |
96 | ||
97 | /* | |
98 | * Rescue workers are used only on emergencies and shared by | |
99 | * all cpus. Give -20. | |
100 | */ | |
101 | RESCUER_NICE_LEVEL = -20, | |
102 | HIGHPRI_NICE_LEVEL = -20, | |
103 | }; | |
104 | ||
105 | /* | |
106 | * Structure fields follow one of the following exclusion rules. | |
107 | * | |
108 | * I: Modifiable by initialization/destruction paths and read-only for | |
109 | * everyone else. | |
110 | * | |
111 | * P: Preemption protected. Disabling preemption is enough and should | |
112 | * only be modified and accessed from the local cpu. | |
113 | * | |
114 | * L: gcwq->lock protected. Access with gcwq->lock held. | |
115 | * | |
116 | * X: During normal operation, modification requires gcwq->lock and | |
117 | * should be done only from local cpu. Either disabling preemption | |
118 | * on local cpu or grabbing gcwq->lock is enough for read access. | |
119 | * If GCWQ_DISASSOCIATED is set, it's identical to L. | |
120 | * | |
121 | * F: wq->flush_mutex protected. | |
122 | * | |
123 | * W: workqueue_lock protected. | |
124 | */ | |
125 | ||
126 | struct global_cwq; | |
127 | struct worker_pool; | |
128 | struct idle_rebind; | |
129 | ||
130 | /* | |
131 | * The poor guys doing the actual heavy lifting. All on-duty workers | |
132 | * are either serving the manager role, on idle list or on busy hash. | |
133 | */ | |
134 | struct worker { | |
135 | /* on idle list while idle, on busy hash table while busy */ | |
136 | union { | |
137 | struct list_head entry; /* L: while idle */ | |
138 | struct hlist_node hentry; /* L: while busy */ | |
139 | }; | |
140 | ||
141 | struct work_struct *current_work; /* L: work being processed */ | |
142 | struct cpu_workqueue_struct *current_cwq; /* L: current_work's cwq */ | |
143 | struct list_head scheduled; /* L: scheduled works */ | |
144 | struct task_struct *task; /* I: worker task */ | |
145 | struct worker_pool *pool; /* I: the associated pool */ | |
146 | /* 64 bytes boundary on 64bit, 32 on 32bit */ | |
147 | unsigned long last_active; /* L: last active timestamp */ | |
148 | unsigned int flags; /* X: flags */ | |
149 | int id; /* I: worker id */ | |
150 | ||
151 | /* for rebinding worker to CPU */ | |
152 | struct idle_rebind *idle_rebind; /* L: for idle worker */ | |
153 | struct work_struct rebind_work; /* L: for busy worker */ | |
154 | }; | |
155 | ||
156 | struct worker_pool { | |
157 | struct global_cwq *gcwq; /* I: the owning gcwq */ | |
158 | unsigned int flags; /* X: flags */ | |
159 | ||
160 | struct list_head worklist; /* L: list of pending works */ | |
161 | int nr_workers; /* L: total number of workers */ | |
162 | int nr_idle; /* L: currently idle ones */ | |
163 | ||
164 | struct list_head idle_list; /* X: list of idle workers */ | |
165 | struct timer_list idle_timer; /* L: worker idle timeout */ | |
166 | struct timer_list mayday_timer; /* L: SOS timer for workers */ | |
167 | ||
168 | struct mutex manager_mutex; /* mutex manager should hold */ | |
169 | struct ida worker_ida; /* L: for worker IDs */ | |
170 | }; | |
171 | ||
172 | /* | |
173 | * Global per-cpu workqueue. There's one and only one for each cpu | |
174 | * and all works are queued and processed here regardless of their | |
175 | * target workqueues. | |
176 | */ | |
177 | struct global_cwq { | |
178 | spinlock_t lock; /* the gcwq lock */ | |
179 | unsigned int cpu; /* I: the associated cpu */ | |
180 | unsigned int flags; /* L: GCWQ_* flags */ | |
181 | ||
182 | /* workers are chained either in busy_hash or pool idle_list */ | |
183 | struct hlist_head busy_hash[BUSY_WORKER_HASH_SIZE]; | |
184 | /* L: hash of busy workers */ | |
185 | ||
186 | struct worker_pool pools[2]; /* normal and highpri pools */ | |
187 | ||
188 | wait_queue_head_t rebind_hold; /* rebind hold wait */ | |
189 | } ____cacheline_aligned_in_smp; | |
190 | ||
191 | /* | |
192 | * The per-CPU workqueue. The lower WORK_STRUCT_FLAG_BITS of | |
193 | * work_struct->data are used for flags and thus cwqs need to be | |
194 | * aligned at two's power of the number of flag bits. | |
195 | */ | |
196 | struct cpu_workqueue_struct { | |
197 | struct worker_pool *pool; /* I: the associated pool */ | |
198 | struct workqueue_struct *wq; /* I: the owning workqueue */ | |
199 | int work_color; /* L: current color */ | |
200 | int flush_color; /* L: flushing color */ | |
201 | int nr_in_flight[WORK_NR_COLORS]; | |
202 | /* L: nr of in_flight works */ | |
203 | int nr_active; /* L: nr of active works */ | |
204 | int max_active; /* L: max active works */ | |
205 | struct list_head delayed_works; /* L: delayed works */ | |
206 | }; | |
207 | ||
208 | /* | |
209 | * Structure used to wait for workqueue flush. | |
210 | */ | |
211 | struct wq_flusher { | |
212 | struct list_head list; /* F: list of flushers */ | |
213 | int flush_color; /* F: flush color waiting for */ | |
214 | struct completion done; /* flush completion */ | |
215 | }; | |
216 | ||
217 | /* | |
218 | * All cpumasks are assumed to be always set on UP and thus can't be | |
219 | * used to determine whether there's something to be done. | |
220 | */ | |
221 | #ifdef CONFIG_SMP | |
222 | typedef cpumask_var_t mayday_mask_t; | |
223 | #define mayday_test_and_set_cpu(cpu, mask) \ | |
224 | cpumask_test_and_set_cpu((cpu), (mask)) | |
225 | #define mayday_clear_cpu(cpu, mask) cpumask_clear_cpu((cpu), (mask)) | |
226 | #define for_each_mayday_cpu(cpu, mask) for_each_cpu((cpu), (mask)) | |
227 | #define alloc_mayday_mask(maskp, gfp) zalloc_cpumask_var((maskp), (gfp)) | |
228 | #define free_mayday_mask(mask) free_cpumask_var((mask)) | |
229 | #else | |
230 | typedef unsigned long mayday_mask_t; | |
231 | #define mayday_test_and_set_cpu(cpu, mask) test_and_set_bit(0, &(mask)) | |
232 | #define mayday_clear_cpu(cpu, mask) clear_bit(0, &(mask)) | |
233 | #define for_each_mayday_cpu(cpu, mask) if ((cpu) = 0, (mask)) | |
234 | #define alloc_mayday_mask(maskp, gfp) true | |
235 | #define free_mayday_mask(mask) do { } while (0) | |
236 | #endif | |
237 | ||
238 | /* | |
239 | * The externally visible workqueue abstraction is an array of | |
240 | * per-CPU workqueues: | |
241 | */ | |
242 | struct workqueue_struct { | |
243 | unsigned int flags; /* W: WQ_* flags */ | |
244 | union { | |
245 | struct cpu_workqueue_struct __percpu *pcpu; | |
246 | struct cpu_workqueue_struct *single; | |
247 | unsigned long v; | |
248 | } cpu_wq; /* I: cwq's */ | |
249 | struct list_head list; /* W: list of all workqueues */ | |
250 | ||
251 | struct mutex flush_mutex; /* protects wq flushing */ | |
252 | int work_color; /* F: current work color */ | |
253 | int flush_color; /* F: current flush color */ | |
254 | atomic_t nr_cwqs_to_flush; /* flush in progress */ | |
255 | struct wq_flusher *first_flusher; /* F: first flusher */ | |
256 | struct list_head flusher_queue; /* F: flush waiters */ | |
257 | struct list_head flusher_overflow; /* F: flush overflow list */ | |
258 | ||
259 | mayday_mask_t mayday_mask; /* cpus requesting rescue */ | |
260 | struct worker *rescuer; /* I: rescue worker */ | |
261 | ||
262 | int nr_drainers; /* W: drain in progress */ | |
263 | int saved_max_active; /* W: saved cwq max_active */ | |
264 | #ifdef CONFIG_LOCKDEP | |
265 | struct lockdep_map lockdep_map; | |
266 | #endif | |
267 | char name[]; /* I: workqueue name */ | |
268 | }; | |
269 | ||
270 | struct workqueue_struct *system_wq __read_mostly; | |
271 | struct workqueue_struct *system_long_wq __read_mostly; | |
272 | struct workqueue_struct *system_nrt_wq __read_mostly; | |
273 | struct workqueue_struct *system_unbound_wq __read_mostly; | |
274 | struct workqueue_struct *system_freezable_wq __read_mostly; | |
275 | struct workqueue_struct *system_nrt_freezable_wq __read_mostly; | |
276 | EXPORT_SYMBOL_GPL(system_wq); | |
277 | EXPORT_SYMBOL_GPL(system_long_wq); | |
278 | EXPORT_SYMBOL_GPL(system_nrt_wq); | |
279 | EXPORT_SYMBOL_GPL(system_unbound_wq); | |
280 | EXPORT_SYMBOL_GPL(system_freezable_wq); | |
281 | EXPORT_SYMBOL_GPL(system_nrt_freezable_wq); | |
282 | ||
283 | #define CREATE_TRACE_POINTS | |
284 | #include <trace/events/workqueue.h> | |
285 | ||
286 | #define for_each_worker_pool(pool, gcwq) \ | |
287 | for ((pool) = &(gcwq)->pools[0]; \ | |
288 | (pool) < &(gcwq)->pools[NR_WORKER_POOLS]; (pool)++) | |
289 | ||
290 | #define for_each_busy_worker(worker, i, pos, gcwq) \ | |
291 | for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) \ | |
292 | hlist_for_each_entry(worker, pos, &gcwq->busy_hash[i], hentry) | |
293 | ||
294 | static inline int __next_gcwq_cpu(int cpu, const struct cpumask *mask, | |
295 | unsigned int sw) | |
296 | { | |
297 | if (cpu < nr_cpu_ids) { | |
298 | if (sw & 1) { | |
299 | cpu = cpumask_next(cpu, mask); | |
300 | if (cpu < nr_cpu_ids) | |
301 | return cpu; | |
302 | } | |
303 | if (sw & 2) | |
304 | return WORK_CPU_UNBOUND; | |
305 | } | |
306 | return WORK_CPU_NONE; | |
307 | } | |
308 | ||
309 | static inline int __next_wq_cpu(int cpu, const struct cpumask *mask, | |
310 | struct workqueue_struct *wq) | |
311 | { | |
312 | return __next_gcwq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2); | |
313 | } | |
314 | ||
315 | /* | |
316 | * CPU iterators | |
317 | * | |
318 | * An extra gcwq is defined for an invalid cpu number | |
319 | * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any | |
320 | * specific CPU. The following iterators are similar to | |
321 | * for_each_*_cpu() iterators but also considers the unbound gcwq. | |
322 | * | |
323 | * for_each_gcwq_cpu() : possible CPUs + WORK_CPU_UNBOUND | |
324 | * for_each_online_gcwq_cpu() : online CPUs + WORK_CPU_UNBOUND | |
325 | * for_each_cwq_cpu() : possible CPUs for bound workqueues, | |
326 | * WORK_CPU_UNBOUND for unbound workqueues | |
327 | */ | |
328 | #define for_each_gcwq_cpu(cpu) \ | |
329 | for ((cpu) = __next_gcwq_cpu(-1, cpu_possible_mask, 3); \ | |
330 | (cpu) < WORK_CPU_NONE; \ | |
331 | (cpu) = __next_gcwq_cpu((cpu), cpu_possible_mask, 3)) | |
332 | ||
333 | #define for_each_online_gcwq_cpu(cpu) \ | |
334 | for ((cpu) = __next_gcwq_cpu(-1, cpu_online_mask, 3); \ | |
335 | (cpu) < WORK_CPU_NONE; \ | |
336 | (cpu) = __next_gcwq_cpu((cpu), cpu_online_mask, 3)) | |
337 | ||
338 | #define for_each_cwq_cpu(cpu, wq) \ | |
339 | for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, (wq)); \ | |
340 | (cpu) < WORK_CPU_NONE; \ | |
341 | (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, (wq))) | |
342 | ||
343 | #ifdef CONFIG_DEBUG_OBJECTS_WORK | |
344 | ||
345 | static struct debug_obj_descr work_debug_descr; | |
346 | ||
347 | static void *work_debug_hint(void *addr) | |
348 | { | |
349 | return ((struct work_struct *) addr)->func; | |
350 | } | |
351 | ||
352 | /* | |
353 | * fixup_init is called when: | |
354 | * - an active object is initialized | |
355 | */ | |
356 | static int work_fixup_init(void *addr, enum debug_obj_state state) | |
357 | { | |
358 | struct work_struct *work = addr; | |
359 | ||
360 | switch (state) { | |
361 | case ODEBUG_STATE_ACTIVE: | |
362 | cancel_work_sync(work); | |
363 | debug_object_init(work, &work_debug_descr); | |
364 | return 1; | |
365 | default: | |
366 | return 0; | |
367 | } | |
368 | } | |
369 | ||
370 | /* | |
371 | * fixup_activate is called when: | |
372 | * - an active object is activated | |
373 | * - an unknown object is activated (might be a statically initialized object) | |
374 | */ | |
375 | static int work_fixup_activate(void *addr, enum debug_obj_state state) | |
376 | { | |
377 | struct work_struct *work = addr; | |
378 | ||
379 | switch (state) { | |
380 | ||
381 | case ODEBUG_STATE_NOTAVAILABLE: | |
382 | /* | |
383 | * This is not really a fixup. The work struct was | |
384 | * statically initialized. We just make sure that it | |
385 | * is tracked in the object tracker. | |
386 | */ | |
387 | if (test_bit(WORK_STRUCT_STATIC_BIT, work_data_bits(work))) { | |
388 | debug_object_init(work, &work_debug_descr); | |
389 | debug_object_activate(work, &work_debug_descr); | |
390 | return 0; | |
391 | } | |
392 | WARN_ON_ONCE(1); | |
393 | return 0; | |
394 | ||
395 | case ODEBUG_STATE_ACTIVE: | |
396 | WARN_ON(1); | |
397 | ||
398 | default: | |
399 | return 0; | |
400 | } | |
401 | } | |
402 | ||
403 | /* | |
404 | * fixup_free is called when: | |
405 | * - an active object is freed | |
406 | */ | |
407 | static int work_fixup_free(void *addr, enum debug_obj_state state) | |
408 | { | |
409 | struct work_struct *work = addr; | |
410 | ||
411 | switch (state) { | |
412 | case ODEBUG_STATE_ACTIVE: | |
413 | cancel_work_sync(work); | |
414 | debug_object_free(work, &work_debug_descr); | |
415 | return 1; | |
416 | default: | |
417 | return 0; | |
418 | } | |
419 | } | |
420 | ||
421 | static struct debug_obj_descr work_debug_descr = { | |
422 | .name = "work_struct", | |
423 | .debug_hint = work_debug_hint, | |
424 | .fixup_init = work_fixup_init, | |
425 | .fixup_activate = work_fixup_activate, | |
426 | .fixup_free = work_fixup_free, | |
427 | }; | |
428 | ||
429 | static inline void debug_work_activate(struct work_struct *work) | |
430 | { | |
431 | debug_object_activate(work, &work_debug_descr); | |
432 | } | |
433 | ||
434 | static inline void debug_work_deactivate(struct work_struct *work) | |
435 | { | |
436 | debug_object_deactivate(work, &work_debug_descr); | |
437 | } | |
438 | ||
439 | void __init_work(struct work_struct *work, int onstack) | |
440 | { | |
441 | if (onstack) | |
442 | debug_object_init_on_stack(work, &work_debug_descr); | |
443 | else | |
444 | debug_object_init(work, &work_debug_descr); | |
445 | } | |
446 | EXPORT_SYMBOL_GPL(__init_work); | |
447 | ||
448 | void destroy_work_on_stack(struct work_struct *work) | |
449 | { | |
450 | debug_object_free(work, &work_debug_descr); | |
451 | } | |
452 | EXPORT_SYMBOL_GPL(destroy_work_on_stack); | |
453 | ||
454 | #else | |
455 | static inline void debug_work_activate(struct work_struct *work) { } | |
456 | static inline void debug_work_deactivate(struct work_struct *work) { } | |
457 | #endif | |
458 | ||
459 | /* Serializes the accesses to the list of workqueues. */ | |
460 | static DEFINE_SPINLOCK(workqueue_lock); | |
461 | static LIST_HEAD(workqueues); | |
462 | static bool workqueue_freezing; /* W: have wqs started freezing? */ | |
463 | ||
464 | /* | |
465 | * The almighty global cpu workqueues. nr_running is the only field | |
466 | * which is expected to be used frequently by other cpus via | |
467 | * try_to_wake_up(). Put it in a separate cacheline. | |
468 | */ | |
469 | static DEFINE_PER_CPU(struct global_cwq, global_cwq); | |
470 | static DEFINE_PER_CPU_SHARED_ALIGNED(atomic_t, pool_nr_running[NR_WORKER_POOLS]); | |
471 | ||
472 | /* | |
473 | * Global cpu workqueue and nr_running counter for unbound gcwq. The | |
474 | * gcwq is always online, has GCWQ_DISASSOCIATED set, and all its | |
475 | * workers have WORKER_UNBOUND set. | |
476 | */ | |
477 | static struct global_cwq unbound_global_cwq; | |
478 | static atomic_t unbound_pool_nr_running[NR_WORKER_POOLS] = { | |
479 | [0 ... NR_WORKER_POOLS - 1] = ATOMIC_INIT(0), /* always 0 */ | |
480 | }; | |
481 | ||
482 | static int worker_thread(void *__worker); | |
483 | ||
484 | static int worker_pool_pri(struct worker_pool *pool) | |
485 | { | |
486 | return pool - pool->gcwq->pools; | |
487 | } | |
488 | ||
489 | static struct global_cwq *get_gcwq(unsigned int cpu) | |
490 | { | |
491 | if (cpu != WORK_CPU_UNBOUND) | |
492 | return &per_cpu(global_cwq, cpu); | |
493 | else | |
494 | return &unbound_global_cwq; | |
495 | } | |
496 | ||
497 | static atomic_t *get_pool_nr_running(struct worker_pool *pool) | |
498 | { | |
499 | int cpu = pool->gcwq->cpu; | |
500 | int idx = worker_pool_pri(pool); | |
501 | ||
502 | if (cpu != WORK_CPU_UNBOUND) | |
503 | return &per_cpu(pool_nr_running, cpu)[idx]; | |
504 | else | |
505 | return &unbound_pool_nr_running[idx]; | |
506 | } | |
507 | ||
508 | static struct cpu_workqueue_struct *get_cwq(unsigned int cpu, | |
509 | struct workqueue_struct *wq) | |
510 | { | |
511 | if (!(wq->flags & WQ_UNBOUND)) { | |
512 | if (likely(cpu < nr_cpu_ids)) | |
513 | return per_cpu_ptr(wq->cpu_wq.pcpu, cpu); | |
514 | } else if (likely(cpu == WORK_CPU_UNBOUND)) | |
515 | return wq->cpu_wq.single; | |
516 | return NULL; | |
517 | } | |
518 | ||
519 | static unsigned int work_color_to_flags(int color) | |
520 | { | |
521 | return color << WORK_STRUCT_COLOR_SHIFT; | |
522 | } | |
523 | ||
524 | static int get_work_color(struct work_struct *work) | |
525 | { | |
526 | return (*work_data_bits(work) >> WORK_STRUCT_COLOR_SHIFT) & | |
527 | ((1 << WORK_STRUCT_COLOR_BITS) - 1); | |
528 | } | |
529 | ||
530 | static int work_next_color(int color) | |
531 | { | |
532 | return (color + 1) % WORK_NR_COLORS; | |
533 | } | |
534 | ||
535 | /* | |
536 | * While queued, %WORK_STRUCT_CWQ is set and non flag bits of a work's data | |
537 | * contain the pointer to the queued cwq. Once execution starts, the flag | |
538 | * is cleared and the high bits contain OFFQ flags and CPU number. | |
539 | * | |
540 | * set_work_cwq(), set_work_cpu_and_clear_pending() and clear_work_data() | |
541 | * can be used to set the cwq, cpu or clear work->data. These functions | |
542 | * should only be called while the work is owned - ie. while the PENDING | |
543 | * bit is set. | |
544 | * | |
545 | * get_work_[g]cwq() can be used to obtain the gcwq or cwq | |
546 | * corresponding to a work. gcwq is available once the work has been | |
547 | * queued anywhere after initialization. cwq is available only from | |
548 | * queueing until execution starts. | |
549 | */ | |
550 | static inline void set_work_data(struct work_struct *work, unsigned long data, | |
551 | unsigned long flags) | |
552 | { | |
553 | BUG_ON(!work_pending(work)); | |
554 | atomic_long_set(&work->data, data | flags | work_static(work)); | |
555 | } | |
556 | ||
557 | static void set_work_cwq(struct work_struct *work, | |
558 | struct cpu_workqueue_struct *cwq, | |
559 | unsigned long extra_flags) | |
560 | { | |
561 | set_work_data(work, (unsigned long)cwq, | |
562 | WORK_STRUCT_PENDING | WORK_STRUCT_CWQ | extra_flags); | |
563 | } | |
564 | ||
565 | static void set_work_cpu_and_clear_pending(struct work_struct *work, | |
566 | unsigned int cpu) | |
567 | { | |
568 | set_work_data(work, (unsigned long)cpu << WORK_OFFQ_CPU_SHIFT, 0); | |
569 | } | |
570 | ||
571 | static void clear_work_data(struct work_struct *work) | |
572 | { | |
573 | set_work_data(work, WORK_STRUCT_NO_CPU, 0); | |
574 | } | |
575 | ||
576 | static struct cpu_workqueue_struct *get_work_cwq(struct work_struct *work) | |
577 | { | |
578 | unsigned long data = atomic_long_read(&work->data); | |
579 | ||
580 | if (data & WORK_STRUCT_CWQ) | |
581 | return (void *)(data & WORK_STRUCT_WQ_DATA_MASK); | |
582 | else | |
583 | return NULL; | |
584 | } | |
585 | ||
586 | static struct global_cwq *get_work_gcwq(struct work_struct *work) | |
587 | { | |
588 | unsigned long data = atomic_long_read(&work->data); | |
589 | unsigned int cpu; | |
590 | ||
591 | if (data & WORK_STRUCT_CWQ) | |
592 | return ((struct cpu_workqueue_struct *) | |
593 | (data & WORK_STRUCT_WQ_DATA_MASK))->pool->gcwq; | |
594 | ||
595 | cpu = data >> WORK_OFFQ_CPU_SHIFT; | |
596 | if (cpu == WORK_CPU_NONE) | |
597 | return NULL; | |
598 | ||
599 | BUG_ON(cpu >= nr_cpu_ids && cpu != WORK_CPU_UNBOUND); | |
600 | return get_gcwq(cpu); | |
601 | } | |
602 | ||
603 | /* | |
604 | * Policy functions. These define the policies on how the global worker | |
605 | * pools are managed. Unless noted otherwise, these functions assume that | |
606 | * they're being called with gcwq->lock held. | |
607 | */ | |
608 | ||
609 | static bool __need_more_worker(struct worker_pool *pool) | |
610 | { | |
611 | return !atomic_read(get_pool_nr_running(pool)); | |
612 | } | |
613 | ||
614 | /* | |
615 | * Need to wake up a worker? Called from anything but currently | |
616 | * running workers. | |
617 | * | |
618 | * Note that, because unbound workers never contribute to nr_running, this | |
619 | * function will always return %true for unbound gcwq as long as the | |
620 | * worklist isn't empty. | |
621 | */ | |
622 | static bool need_more_worker(struct worker_pool *pool) | |
623 | { | |
624 | return !list_empty(&pool->worklist) && __need_more_worker(pool); | |
625 | } | |
626 | ||
627 | /* Can I start working? Called from busy but !running workers. */ | |
628 | static bool may_start_working(struct worker_pool *pool) | |
629 | { | |
630 | return pool->nr_idle; | |
631 | } | |
632 | ||
633 | /* Do I need to keep working? Called from currently running workers. */ | |
634 | static bool keep_working(struct worker_pool *pool) | |
635 | { | |
636 | atomic_t *nr_running = get_pool_nr_running(pool); | |
637 | ||
638 | return !list_empty(&pool->worklist) && atomic_read(nr_running) <= 1; | |
639 | } | |
640 | ||
641 | /* Do we need a new worker? Called from manager. */ | |
642 | static bool need_to_create_worker(struct worker_pool *pool) | |
643 | { | |
644 | return need_more_worker(pool) && !may_start_working(pool); | |
645 | } | |
646 | ||
647 | /* Do I need to be the manager? */ | |
648 | static bool need_to_manage_workers(struct worker_pool *pool) | |
649 | { | |
650 | return need_to_create_worker(pool) || | |
651 | (pool->flags & POOL_MANAGE_WORKERS); | |
652 | } | |
653 | ||
654 | /* Do we have too many workers and should some go away? */ | |
655 | static bool too_many_workers(struct worker_pool *pool) | |
656 | { | |
657 | bool managing = mutex_is_locked(&pool->manager_mutex); | |
658 | int nr_idle = pool->nr_idle + managing; /* manager is considered idle */ | |
659 | int nr_busy = pool->nr_workers - nr_idle; | |
660 | ||
661 | return nr_idle > 2 && (nr_idle - 2) * MAX_IDLE_WORKERS_RATIO >= nr_busy; | |
662 | } | |
663 | ||
664 | /* | |
665 | * Wake up functions. | |
666 | */ | |
667 | ||
668 | /* Return the first worker. Safe with preemption disabled */ | |
669 | static struct worker *first_worker(struct worker_pool *pool) | |
670 | { | |
671 | if (unlikely(list_empty(&pool->idle_list))) | |
672 | return NULL; | |
673 | ||
674 | return list_first_entry(&pool->idle_list, struct worker, entry); | |
675 | } | |
676 | ||
677 | /** | |
678 | * wake_up_worker - wake up an idle worker | |
679 | * @pool: worker pool to wake worker from | |
680 | * | |
681 | * Wake up the first idle worker of @pool. | |
682 | * | |
683 | * CONTEXT: | |
684 | * spin_lock_irq(gcwq->lock). | |
685 | */ | |
686 | static void wake_up_worker(struct worker_pool *pool) | |
687 | { | |
688 | struct worker *worker = first_worker(pool); | |
689 | ||
690 | if (likely(worker)) | |
691 | wake_up_process(worker->task); | |
692 | } | |
693 | ||
694 | /** | |
695 | * wq_worker_waking_up - a worker is waking up | |
696 | * @task: task waking up | |
697 | * @cpu: CPU @task is waking up to | |
698 | * | |
699 | * This function is called during try_to_wake_up() when a worker is | |
700 | * being awoken. | |
701 | * | |
702 | * CONTEXT: | |
703 | * spin_lock_irq(rq->lock) | |
704 | */ | |
705 | void wq_worker_waking_up(struct task_struct *task, unsigned int cpu) | |
706 | { | |
707 | struct worker *worker = kthread_data(task); | |
708 | ||
709 | if (!(worker->flags & WORKER_NOT_RUNNING)) | |
710 | atomic_inc(get_pool_nr_running(worker->pool)); | |
711 | } | |
712 | ||
713 | /** | |
714 | * wq_worker_sleeping - a worker is going to sleep | |
715 | * @task: task going to sleep | |
716 | * @cpu: CPU in question, must be the current CPU number | |
717 | * | |
718 | * This function is called during schedule() when a busy worker is | |
719 | * going to sleep. Worker on the same cpu can be woken up by | |
720 | * returning pointer to its task. | |
721 | * | |
722 | * CONTEXT: | |
723 | * spin_lock_irq(rq->lock) | |
724 | * | |
725 | * RETURNS: | |
726 | * Worker task on @cpu to wake up, %NULL if none. | |
727 | */ | |
728 | struct task_struct *wq_worker_sleeping(struct task_struct *task, | |
729 | unsigned int cpu) | |
730 | { | |
731 | struct worker *worker = kthread_data(task), *to_wakeup = NULL; | |
732 | struct worker_pool *pool = worker->pool; | |
733 | atomic_t *nr_running = get_pool_nr_running(pool); | |
734 | ||
735 | if (worker->flags & WORKER_NOT_RUNNING) | |
736 | return NULL; | |
737 | ||
738 | /* this can only happen on the local cpu */ | |
739 | BUG_ON(cpu != raw_smp_processor_id()); | |
740 | ||
741 | /* | |
742 | * The counterpart of the following dec_and_test, implied mb, | |
743 | * worklist not empty test sequence is in insert_work(). | |
744 | * Please read comment there. | |
745 | * | |
746 | * NOT_RUNNING is clear. This means that we're bound to and | |
747 | * running on the local cpu w/ rq lock held and preemption | |
748 | * disabled, which in turn means that none else could be | |
749 | * manipulating idle_list, so dereferencing idle_list without gcwq | |
750 | * lock is safe. | |
751 | */ | |
752 | if (atomic_dec_and_test(nr_running) && !list_empty(&pool->worklist)) | |
753 | to_wakeup = first_worker(pool); | |
754 | return to_wakeup ? to_wakeup->task : NULL; | |
755 | } | |
756 | ||
757 | /** | |
758 | * worker_set_flags - set worker flags and adjust nr_running accordingly | |
759 | * @worker: self | |
760 | * @flags: flags to set | |
761 | * @wakeup: wakeup an idle worker if necessary | |
762 | * | |
763 | * Set @flags in @worker->flags and adjust nr_running accordingly. If | |
764 | * nr_running becomes zero and @wakeup is %true, an idle worker is | |
765 | * woken up. | |
766 | * | |
767 | * CONTEXT: | |
768 | * spin_lock_irq(gcwq->lock) | |
769 | */ | |
770 | static inline void worker_set_flags(struct worker *worker, unsigned int flags, | |
771 | bool wakeup) | |
772 | { | |
773 | struct worker_pool *pool = worker->pool; | |
774 | ||
775 | WARN_ON_ONCE(worker->task != current); | |
776 | ||
777 | /* | |
778 | * If transitioning into NOT_RUNNING, adjust nr_running and | |
779 | * wake up an idle worker as necessary if requested by | |
780 | * @wakeup. | |
781 | */ | |
782 | if ((flags & WORKER_NOT_RUNNING) && | |
783 | !(worker->flags & WORKER_NOT_RUNNING)) { | |
784 | atomic_t *nr_running = get_pool_nr_running(pool); | |
785 | ||
786 | if (wakeup) { | |
787 | if (atomic_dec_and_test(nr_running) && | |
788 | !list_empty(&pool->worklist)) | |
789 | wake_up_worker(pool); | |
790 | } else | |
791 | atomic_dec(nr_running); | |
792 | } | |
793 | ||
794 | worker->flags |= flags; | |
795 | } | |
796 | ||
797 | /** | |
798 | * worker_clr_flags - clear worker flags and adjust nr_running accordingly | |
799 | * @worker: self | |
800 | * @flags: flags to clear | |
801 | * | |
802 | * Clear @flags in @worker->flags and adjust nr_running accordingly. | |
803 | * | |
804 | * CONTEXT: | |
805 | * spin_lock_irq(gcwq->lock) | |
806 | */ | |
807 | static inline void worker_clr_flags(struct worker *worker, unsigned int flags) | |
808 | { | |
809 | struct worker_pool *pool = worker->pool; | |
810 | unsigned int oflags = worker->flags; | |
811 | ||
812 | WARN_ON_ONCE(worker->task != current); | |
813 | ||
814 | worker->flags &= ~flags; | |
815 | ||
816 | /* | |
817 | * If transitioning out of NOT_RUNNING, increment nr_running. Note | |
818 | * that the nested NOT_RUNNING is not a noop. NOT_RUNNING is mask | |
819 | * of multiple flags, not a single flag. | |
820 | */ | |
821 | if ((flags & WORKER_NOT_RUNNING) && (oflags & WORKER_NOT_RUNNING)) | |
822 | if (!(worker->flags & WORKER_NOT_RUNNING)) | |
823 | atomic_inc(get_pool_nr_running(pool)); | |
824 | } | |
825 | ||
826 | /** | |
827 | * busy_worker_head - return the busy hash head for a work | |
828 | * @gcwq: gcwq of interest | |
829 | * @work: work to be hashed | |
830 | * | |
831 | * Return hash head of @gcwq for @work. | |
832 | * | |
833 | * CONTEXT: | |
834 | * spin_lock_irq(gcwq->lock). | |
835 | * | |
836 | * RETURNS: | |
837 | * Pointer to the hash head. | |
838 | */ | |
839 | static struct hlist_head *busy_worker_head(struct global_cwq *gcwq, | |
840 | struct work_struct *work) | |
841 | { | |
842 | const int base_shift = ilog2(sizeof(struct work_struct)); | |
843 | unsigned long v = (unsigned long)work; | |
844 | ||
845 | /* simple shift and fold hash, do we need something better? */ | |
846 | v >>= base_shift; | |
847 | v += v >> BUSY_WORKER_HASH_ORDER; | |
848 | v &= BUSY_WORKER_HASH_MASK; | |
849 | ||
850 | return &gcwq->busy_hash[v]; | |
851 | } | |
852 | ||
853 | /** | |
854 | * __find_worker_executing_work - find worker which is executing a work | |
855 | * @gcwq: gcwq of interest | |
856 | * @bwh: hash head as returned by busy_worker_head() | |
857 | * @work: work to find worker for | |
858 | * | |
859 | * Find a worker which is executing @work on @gcwq. @bwh should be | |
860 | * the hash head obtained by calling busy_worker_head() with the same | |
861 | * work. | |
862 | * | |
863 | * CONTEXT: | |
864 | * spin_lock_irq(gcwq->lock). | |
865 | * | |
866 | * RETURNS: | |
867 | * Pointer to worker which is executing @work if found, NULL | |
868 | * otherwise. | |
869 | */ | |
870 | static struct worker *__find_worker_executing_work(struct global_cwq *gcwq, | |
871 | struct hlist_head *bwh, | |
872 | struct work_struct *work) | |
873 | { | |
874 | struct worker *worker; | |
875 | struct hlist_node *tmp; | |
876 | ||
877 | hlist_for_each_entry(worker, tmp, bwh, hentry) | |
878 | if (worker->current_work == work) | |
879 | return worker; | |
880 | return NULL; | |
881 | } | |
882 | ||
883 | /** | |
884 | * find_worker_executing_work - find worker which is executing a work | |
885 | * @gcwq: gcwq of interest | |
886 | * @work: work to find worker for | |
887 | * | |
888 | * Find a worker which is executing @work on @gcwq. This function is | |
889 | * identical to __find_worker_executing_work() except that this | |
890 | * function calculates @bwh itself. | |
891 | * | |
892 | * CONTEXT: | |
893 | * spin_lock_irq(gcwq->lock). | |
894 | * | |
895 | * RETURNS: | |
896 | * Pointer to worker which is executing @work if found, NULL | |
897 | * otherwise. | |
898 | */ | |
899 | static struct worker *find_worker_executing_work(struct global_cwq *gcwq, | |
900 | struct work_struct *work) | |
901 | { | |
902 | return __find_worker_executing_work(gcwq, busy_worker_head(gcwq, work), | |
903 | work); | |
904 | } | |
905 | ||
906 | /** | |
907 | * move_linked_works - move linked works to a list | |
908 | * @work: start of series of works to be scheduled | |
909 | * @head: target list to append @work to | |
910 | * @nextp: out paramter for nested worklist walking | |
911 | * | |
912 | * Schedule linked works starting from @work to @head. Work series to | |
913 | * be scheduled starts at @work and includes any consecutive work with | |
914 | * WORK_STRUCT_LINKED set in its predecessor. | |
915 | * | |
916 | * If @nextp is not NULL, it's updated to point to the next work of | |
917 | * the last scheduled work. This allows move_linked_works() to be | |
918 | * nested inside outer list_for_each_entry_safe(). | |
919 | * | |
920 | * CONTEXT: | |
921 | * spin_lock_irq(gcwq->lock). | |
922 | */ | |
923 | static void move_linked_works(struct work_struct *work, struct list_head *head, | |
924 | struct work_struct **nextp) | |
925 | { | |
926 | struct work_struct *n; | |
927 | ||
928 | /* | |
929 | * Linked worklist will always end before the end of the list, | |
930 | * use NULL for list head. | |
931 | */ | |
932 | list_for_each_entry_safe_from(work, n, NULL, entry) { | |
933 | list_move_tail(&work->entry, head); | |
934 | if (!(*work_data_bits(work) & WORK_STRUCT_LINKED)) | |
935 | break; | |
936 | } | |
937 | ||
938 | /* | |
939 | * If we're already inside safe list traversal and have moved | |
940 | * multiple works to the scheduled queue, the next position | |
941 | * needs to be updated. | |
942 | */ | |
943 | if (nextp) | |
944 | *nextp = n; | |
945 | } | |
946 | ||
947 | static void cwq_activate_first_delayed(struct cpu_workqueue_struct *cwq) | |
948 | { | |
949 | struct work_struct *work = list_first_entry(&cwq->delayed_works, | |
950 | struct work_struct, entry); | |
951 | ||
952 | trace_workqueue_activate_work(work); | |
953 | move_linked_works(work, &cwq->pool->worklist, NULL); | |
954 | __clear_bit(WORK_STRUCT_DELAYED_BIT, work_data_bits(work)); | |
955 | cwq->nr_active++; | |
956 | } | |
957 | ||
958 | /** | |
959 | * cwq_dec_nr_in_flight - decrement cwq's nr_in_flight | |
960 | * @cwq: cwq of interest | |
961 | * @color: color of work which left the queue | |
962 | * @delayed: for a delayed work | |
963 | * | |
964 | * A work either has completed or is removed from pending queue, | |
965 | * decrement nr_in_flight of its cwq and handle workqueue flushing. | |
966 | * | |
967 | * CONTEXT: | |
968 | * spin_lock_irq(gcwq->lock). | |
969 | */ | |
970 | static void cwq_dec_nr_in_flight(struct cpu_workqueue_struct *cwq, int color, | |
971 | bool delayed) | |
972 | { | |
973 | /* ignore uncolored works */ | |
974 | if (color == WORK_NO_COLOR) | |
975 | return; | |
976 | ||
977 | cwq->nr_in_flight[color]--; | |
978 | ||
979 | if (!delayed) { | |
980 | cwq->nr_active--; | |
981 | if (!list_empty(&cwq->delayed_works)) { | |
982 | /* one down, submit a delayed one */ | |
983 | if (cwq->nr_active < cwq->max_active) | |
984 | cwq_activate_first_delayed(cwq); | |
985 | } | |
986 | } | |
987 | ||
988 | /* is flush in progress and are we at the flushing tip? */ | |
989 | if (likely(cwq->flush_color != color)) | |
990 | return; | |
991 | ||
992 | /* are there still in-flight works? */ | |
993 | if (cwq->nr_in_flight[color]) | |
994 | return; | |
995 | ||
996 | /* this cwq is done, clear flush_color */ | |
997 | cwq->flush_color = -1; | |
998 | ||
999 | /* | |
1000 | * If this was the last cwq, wake up the first flusher. It | |
1001 | * will handle the rest. | |
1002 | */ | |
1003 | if (atomic_dec_and_test(&cwq->wq->nr_cwqs_to_flush)) | |
1004 | complete(&cwq->wq->first_flusher->done); | |
1005 | } | |
1006 | ||
1007 | /* | |
1008 | * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit, | |
1009 | * so this work can't be re-armed in any way. | |
1010 | */ | |
1011 | static int try_to_grab_pending(struct work_struct *work) | |
1012 | { | |
1013 | struct global_cwq *gcwq; | |
1014 | int ret = -1; | |
1015 | ||
1016 | if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) | |
1017 | return 0; | |
1018 | ||
1019 | /* | |
1020 | * The queueing is in progress, or it is already queued. Try to | |
1021 | * steal it from ->worklist without clearing WORK_STRUCT_PENDING. | |
1022 | */ | |
1023 | gcwq = get_work_gcwq(work); | |
1024 | if (!gcwq) | |
1025 | return ret; | |
1026 | ||
1027 | spin_lock_irq(&gcwq->lock); | |
1028 | if (!list_empty(&work->entry)) { | |
1029 | /* | |
1030 | * This work is queued, but perhaps we locked the wrong gcwq. | |
1031 | * In that case we must see the new value after rmb(), see | |
1032 | * insert_work()->wmb(). | |
1033 | */ | |
1034 | smp_rmb(); | |
1035 | if (gcwq == get_work_gcwq(work)) { | |
1036 | debug_work_deactivate(work); | |
1037 | list_del_init(&work->entry); | |
1038 | cwq_dec_nr_in_flight(get_work_cwq(work), | |
1039 | get_work_color(work), | |
1040 | *work_data_bits(work) & WORK_STRUCT_DELAYED); | |
1041 | ret = 1; | |
1042 | } | |
1043 | } | |
1044 | spin_unlock_irq(&gcwq->lock); | |
1045 | ||
1046 | return ret; | |
1047 | } | |
1048 | ||
1049 | /** | |
1050 | * insert_work - insert a work into gcwq | |
1051 | * @cwq: cwq @work belongs to | |
1052 | * @work: work to insert | |
1053 | * @head: insertion point | |
1054 | * @extra_flags: extra WORK_STRUCT_* flags to set | |
1055 | * | |
1056 | * Insert @work which belongs to @cwq into @gcwq after @head. | |
1057 | * @extra_flags is or'd to work_struct flags. | |
1058 | * | |
1059 | * CONTEXT: | |
1060 | * spin_lock_irq(gcwq->lock). | |
1061 | */ | |
1062 | static void insert_work(struct cpu_workqueue_struct *cwq, | |
1063 | struct work_struct *work, struct list_head *head, | |
1064 | unsigned int extra_flags) | |
1065 | { | |
1066 | struct worker_pool *pool = cwq->pool; | |
1067 | ||
1068 | /* we own @work, set data and link */ | |
1069 | set_work_cwq(work, cwq, extra_flags); | |
1070 | ||
1071 | /* | |
1072 | * Ensure that we get the right work->data if we see the | |
1073 | * result of list_add() below, see try_to_grab_pending(). | |
1074 | */ | |
1075 | smp_wmb(); | |
1076 | ||
1077 | list_add_tail(&work->entry, head); | |
1078 | ||
1079 | /* | |
1080 | * Ensure either worker_sched_deactivated() sees the above | |
1081 | * list_add_tail() or we see zero nr_running to avoid workers | |
1082 | * lying around lazily while there are works to be processed. | |
1083 | */ | |
1084 | smp_mb(); | |
1085 | ||
1086 | if (__need_more_worker(pool)) | |
1087 | wake_up_worker(pool); | |
1088 | } | |
1089 | ||
1090 | /* | |
1091 | * Test whether @work is being queued from another work executing on the | |
1092 | * same workqueue. This is rather expensive and should only be used from | |
1093 | * cold paths. | |
1094 | */ | |
1095 | static bool is_chained_work(struct workqueue_struct *wq) | |
1096 | { | |
1097 | unsigned long flags; | |
1098 | unsigned int cpu; | |
1099 | ||
1100 | for_each_gcwq_cpu(cpu) { | |
1101 | struct global_cwq *gcwq = get_gcwq(cpu); | |
1102 | struct worker *worker; | |
1103 | struct hlist_node *pos; | |
1104 | int i; | |
1105 | ||
1106 | spin_lock_irqsave(&gcwq->lock, flags); | |
1107 | for_each_busy_worker(worker, i, pos, gcwq) { | |
1108 | if (worker->task != current) | |
1109 | continue; | |
1110 | spin_unlock_irqrestore(&gcwq->lock, flags); | |
1111 | /* | |
1112 | * I'm @worker, no locking necessary. See if @work | |
1113 | * is headed to the same workqueue. | |
1114 | */ | |
1115 | return worker->current_cwq->wq == wq; | |
1116 | } | |
1117 | spin_unlock_irqrestore(&gcwq->lock, flags); | |
1118 | } | |
1119 | return false; | |
1120 | } | |
1121 | ||
1122 | static void __queue_work(unsigned int cpu, struct workqueue_struct *wq, | |
1123 | struct work_struct *work) | |
1124 | { | |
1125 | struct global_cwq *gcwq; | |
1126 | struct cpu_workqueue_struct *cwq; | |
1127 | struct list_head *worklist; | |
1128 | unsigned int work_flags; | |
1129 | ||
1130 | /* | |
1131 | * While a work item is PENDING && off queue, a task trying to | |
1132 | * steal the PENDING will busy-loop waiting for it to either get | |
1133 | * queued or lose PENDING. Grabbing PENDING and queueing should | |
1134 | * happen with IRQ disabled. | |
1135 | */ | |
1136 | WARN_ON_ONCE(!irqs_disabled()); | |
1137 | ||
1138 | debug_work_activate(work); | |
1139 | ||
1140 | /* if dying, only works from the same workqueue are allowed */ | |
1141 | if (unlikely(wq->flags & WQ_DRAINING) && | |
1142 | WARN_ON_ONCE(!is_chained_work(wq))) | |
1143 | return; | |
1144 | ||
1145 | /* determine gcwq to use */ | |
1146 | if (!(wq->flags & WQ_UNBOUND)) { | |
1147 | struct global_cwq *last_gcwq; | |
1148 | ||
1149 | if (cpu == WORK_CPU_UNBOUND) | |
1150 | cpu = raw_smp_processor_id(); | |
1151 | ||
1152 | /* | |
1153 | * It's multi cpu. If @wq is non-reentrant and @work | |
1154 | * was previously on a different cpu, it might still | |
1155 | * be running there, in which case the work needs to | |
1156 | * be queued on that cpu to guarantee non-reentrance. | |
1157 | */ | |
1158 | gcwq = get_gcwq(cpu); | |
1159 | if (wq->flags & WQ_NON_REENTRANT && | |
1160 | (last_gcwq = get_work_gcwq(work)) && last_gcwq != gcwq) { | |
1161 | struct worker *worker; | |
1162 | ||
1163 | spin_lock(&last_gcwq->lock); | |
1164 | ||
1165 | worker = find_worker_executing_work(last_gcwq, work); | |
1166 | ||
1167 | if (worker && worker->current_cwq->wq == wq) | |
1168 | gcwq = last_gcwq; | |
1169 | else { | |
1170 | /* meh... not running there, queue here */ | |
1171 | spin_unlock(&last_gcwq->lock); | |
1172 | spin_lock(&gcwq->lock); | |
1173 | } | |
1174 | } else { | |
1175 | spin_lock(&gcwq->lock); | |
1176 | } | |
1177 | } else { | |
1178 | gcwq = get_gcwq(WORK_CPU_UNBOUND); | |
1179 | spin_lock(&gcwq->lock); | |
1180 | } | |
1181 | ||
1182 | /* gcwq determined, get cwq and queue */ | |
1183 | cwq = get_cwq(gcwq->cpu, wq); | |
1184 | trace_workqueue_queue_work(cpu, cwq, work); | |
1185 | ||
1186 | if (WARN_ON(!list_empty(&work->entry))) { | |
1187 | spin_unlock(&gcwq->lock); | |
1188 | return; | |
1189 | } | |
1190 | ||
1191 | cwq->nr_in_flight[cwq->work_color]++; | |
1192 | work_flags = work_color_to_flags(cwq->work_color); | |
1193 | ||
1194 | if (likely(cwq->nr_active < cwq->max_active)) { | |
1195 | trace_workqueue_activate_work(work); | |
1196 | cwq->nr_active++; | |
1197 | worklist = &cwq->pool->worklist; | |
1198 | } else { | |
1199 | work_flags |= WORK_STRUCT_DELAYED; | |
1200 | worklist = &cwq->delayed_works; | |
1201 | } | |
1202 | ||
1203 | insert_work(cwq, work, worklist, work_flags); | |
1204 | ||
1205 | spin_unlock(&gcwq->lock); | |
1206 | } | |
1207 | ||
1208 | /** | |
1209 | * queue_work_on - queue work on specific cpu | |
1210 | * @cpu: CPU number to execute work on | |
1211 | * @wq: workqueue to use | |
1212 | * @work: work to queue | |
1213 | * | |
1214 | * Returns %false if @work was already on a queue, %true otherwise. | |
1215 | * | |
1216 | * We queue the work to a specific CPU, the caller must ensure it | |
1217 | * can't go away. | |
1218 | */ | |
1219 | bool queue_work_on(int cpu, struct workqueue_struct *wq, | |
1220 | struct work_struct *work) | |
1221 | { | |
1222 | bool ret = false; | |
1223 | unsigned long flags; | |
1224 | ||
1225 | local_irq_save(flags); | |
1226 | ||
1227 | if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { | |
1228 | __queue_work(cpu, wq, work); | |
1229 | ret = true; | |
1230 | } | |
1231 | ||
1232 | local_irq_restore(flags); | |
1233 | return ret; | |
1234 | } | |
1235 | EXPORT_SYMBOL_GPL(queue_work_on); | |
1236 | ||
1237 | /** | |
1238 | * queue_work - queue work on a workqueue | |
1239 | * @wq: workqueue to use | |
1240 | * @work: work to queue | |
1241 | * | |
1242 | * Returns %false if @work was already on a queue, %true otherwise. | |
1243 | * | |
1244 | * We queue the work to the CPU on which it was submitted, but if the CPU dies | |
1245 | * it can be processed by another CPU. | |
1246 | */ | |
1247 | bool queue_work(struct workqueue_struct *wq, struct work_struct *work) | |
1248 | { | |
1249 | return queue_work_on(WORK_CPU_UNBOUND, wq, work); | |
1250 | } | |
1251 | EXPORT_SYMBOL_GPL(queue_work); | |
1252 | ||
1253 | void delayed_work_timer_fn(unsigned long __data) | |
1254 | { | |
1255 | struct delayed_work *dwork = (struct delayed_work *)__data; | |
1256 | struct cpu_workqueue_struct *cwq = get_work_cwq(&dwork->work); | |
1257 | ||
1258 | local_irq_disable(); | |
1259 | __queue_work(WORK_CPU_UNBOUND, cwq->wq, &dwork->work); | |
1260 | local_irq_enable(); | |
1261 | } | |
1262 | EXPORT_SYMBOL_GPL(delayed_work_timer_fn); | |
1263 | ||
1264 | static void __queue_delayed_work(int cpu, struct workqueue_struct *wq, | |
1265 | struct delayed_work *dwork, unsigned long delay) | |
1266 | { | |
1267 | struct timer_list *timer = &dwork->timer; | |
1268 | struct work_struct *work = &dwork->work; | |
1269 | unsigned int lcpu; | |
1270 | ||
1271 | WARN_ON_ONCE(timer->function != delayed_work_timer_fn || | |
1272 | timer->data != (unsigned long)dwork); | |
1273 | BUG_ON(timer_pending(timer)); | |
1274 | BUG_ON(!list_empty(&work->entry)); | |
1275 | ||
1276 | timer_stats_timer_set_start_info(&dwork->timer); | |
1277 | ||
1278 | /* | |
1279 | * This stores cwq for the moment, for the timer_fn. Note that the | |
1280 | * work's gcwq is preserved to allow reentrance detection for | |
1281 | * delayed works. | |
1282 | */ | |
1283 | if (!(wq->flags & WQ_UNBOUND)) { | |
1284 | struct global_cwq *gcwq = get_work_gcwq(work); | |
1285 | ||
1286 | if (gcwq && gcwq->cpu != WORK_CPU_UNBOUND) | |
1287 | lcpu = gcwq->cpu; | |
1288 | else | |
1289 | lcpu = raw_smp_processor_id(); | |
1290 | } else { | |
1291 | lcpu = WORK_CPU_UNBOUND; | |
1292 | } | |
1293 | ||
1294 | set_work_cwq(work, get_cwq(lcpu, wq), 0); | |
1295 | ||
1296 | timer->expires = jiffies + delay; | |
1297 | ||
1298 | if (unlikely(cpu != WORK_CPU_UNBOUND)) | |
1299 | add_timer_on(timer, cpu); | |
1300 | else | |
1301 | add_timer(timer); | |
1302 | } | |
1303 | ||
1304 | /** | |
1305 | * queue_delayed_work_on - queue work on specific CPU after delay | |
1306 | * @cpu: CPU number to execute work on | |
1307 | * @wq: workqueue to use | |
1308 | * @dwork: work to queue | |
1309 | * @delay: number of jiffies to wait before queueing | |
1310 | * | |
1311 | * Returns %false if @work was already on a queue, %true otherwise. If | |
1312 | * @delay is zero and @dwork is idle, it will be scheduled for immediate | |
1313 | * execution. | |
1314 | */ | |
1315 | bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq, | |
1316 | struct delayed_work *dwork, unsigned long delay) | |
1317 | { | |
1318 | struct work_struct *work = &dwork->work; | |
1319 | bool ret = false; | |
1320 | unsigned long flags; | |
1321 | ||
1322 | if (!delay) | |
1323 | return queue_work_on(cpu, wq, &dwork->work); | |
1324 | ||
1325 | /* read the comment in __queue_work() */ | |
1326 | local_irq_save(flags); | |
1327 | ||
1328 | if (!test_and_set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))) { | |
1329 | __queue_delayed_work(cpu, wq, dwork, delay); | |
1330 | ret = true; | |
1331 | } | |
1332 | ||
1333 | local_irq_restore(flags); | |
1334 | return ret; | |
1335 | } | |
1336 | EXPORT_SYMBOL_GPL(queue_delayed_work_on); | |
1337 | ||
1338 | /** | |
1339 | * queue_delayed_work - queue work on a workqueue after delay | |
1340 | * @wq: workqueue to use | |
1341 | * @dwork: delayable work to queue | |
1342 | * @delay: number of jiffies to wait before queueing | |
1343 | * | |
1344 | * Equivalent to queue_delayed_work_on() but tries to use the local CPU. | |
1345 | */ | |
1346 | bool queue_delayed_work(struct workqueue_struct *wq, | |
1347 | struct delayed_work *dwork, unsigned long delay) | |
1348 | { | |
1349 | return queue_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay); | |
1350 | } | |
1351 | EXPORT_SYMBOL_GPL(queue_delayed_work); | |
1352 | ||
1353 | /** | |
1354 | * worker_enter_idle - enter idle state | |
1355 | * @worker: worker which is entering idle state | |
1356 | * | |
1357 | * @worker is entering idle state. Update stats and idle timer if | |
1358 | * necessary. | |
1359 | * | |
1360 | * LOCKING: | |
1361 | * spin_lock_irq(gcwq->lock). | |
1362 | */ | |
1363 | static void worker_enter_idle(struct worker *worker) | |
1364 | { | |
1365 | struct worker_pool *pool = worker->pool; | |
1366 | struct global_cwq *gcwq = pool->gcwq; | |
1367 | ||
1368 | BUG_ON(worker->flags & WORKER_IDLE); | |
1369 | BUG_ON(!list_empty(&worker->entry) && | |
1370 | (worker->hentry.next || worker->hentry.pprev)); | |
1371 | ||
1372 | /* can't use worker_set_flags(), also called from start_worker() */ | |
1373 | worker->flags |= WORKER_IDLE; | |
1374 | pool->nr_idle++; | |
1375 | worker->last_active = jiffies; | |
1376 | ||
1377 | /* idle_list is LIFO */ | |
1378 | list_add(&worker->entry, &pool->idle_list); | |
1379 | ||
1380 | if (too_many_workers(pool) && !timer_pending(&pool->idle_timer)) | |
1381 | mod_timer(&pool->idle_timer, jiffies + IDLE_WORKER_TIMEOUT); | |
1382 | ||
1383 | /* | |
1384 | * Sanity check nr_running. Because gcwq_unbind_fn() releases | |
1385 | * gcwq->lock between setting %WORKER_UNBOUND and zapping | |
1386 | * nr_running, the warning may trigger spuriously. Check iff | |
1387 | * unbind is not in progress. | |
1388 | */ | |
1389 | WARN_ON_ONCE(!(gcwq->flags & GCWQ_DISASSOCIATED) && | |
1390 | pool->nr_workers == pool->nr_idle && | |
1391 | atomic_read(get_pool_nr_running(pool))); | |
1392 | } | |
1393 | ||
1394 | /** | |
1395 | * worker_leave_idle - leave idle state | |
1396 | * @worker: worker which is leaving idle state | |
1397 | * | |
1398 | * @worker is leaving idle state. Update stats. | |
1399 | * | |
1400 | * LOCKING: | |
1401 | * spin_lock_irq(gcwq->lock). | |
1402 | */ | |
1403 | static void worker_leave_idle(struct worker *worker) | |
1404 | { | |
1405 | struct worker_pool *pool = worker->pool; | |
1406 | ||
1407 | BUG_ON(!(worker->flags & WORKER_IDLE)); | |
1408 | worker_clr_flags(worker, WORKER_IDLE); | |
1409 | pool->nr_idle--; | |
1410 | list_del_init(&worker->entry); | |
1411 | } | |
1412 | ||
1413 | /** | |
1414 | * worker_maybe_bind_and_lock - bind worker to its cpu if possible and lock gcwq | |
1415 | * @worker: self | |
1416 | * | |
1417 | * Works which are scheduled while the cpu is online must at least be | |
1418 | * scheduled to a worker which is bound to the cpu so that if they are | |
1419 | * flushed from cpu callbacks while cpu is going down, they are | |
1420 | * guaranteed to execute on the cpu. | |
1421 | * | |
1422 | * This function is to be used by rogue workers and rescuers to bind | |
1423 | * themselves to the target cpu and may race with cpu going down or | |
1424 | * coming online. kthread_bind() can't be used because it may put the | |
1425 | * worker to already dead cpu and set_cpus_allowed_ptr() can't be used | |
1426 | * verbatim as it's best effort and blocking and gcwq may be | |
1427 | * [dis]associated in the meantime. | |
1428 | * | |
1429 | * This function tries set_cpus_allowed() and locks gcwq and verifies the | |
1430 | * binding against %GCWQ_DISASSOCIATED which is set during | |
1431 | * %CPU_DOWN_PREPARE and cleared during %CPU_ONLINE, so if the worker | |
1432 | * enters idle state or fetches works without dropping lock, it can | |
1433 | * guarantee the scheduling requirement described in the first paragraph. | |
1434 | * | |
1435 | * CONTEXT: | |
1436 | * Might sleep. Called without any lock but returns with gcwq->lock | |
1437 | * held. | |
1438 | * | |
1439 | * RETURNS: | |
1440 | * %true if the associated gcwq is online (@worker is successfully | |
1441 | * bound), %false if offline. | |
1442 | */ | |
1443 | static bool worker_maybe_bind_and_lock(struct worker *worker) | |
1444 | __acquires(&gcwq->lock) | |
1445 | { | |
1446 | struct global_cwq *gcwq = worker->pool->gcwq; | |
1447 | struct task_struct *task = worker->task; | |
1448 | ||
1449 | while (true) { | |
1450 | /* | |
1451 | * The following call may fail, succeed or succeed | |
1452 | * without actually migrating the task to the cpu if | |
1453 | * it races with cpu hotunplug operation. Verify | |
1454 | * against GCWQ_DISASSOCIATED. | |
1455 | */ | |
1456 | if (!(gcwq->flags & GCWQ_DISASSOCIATED)) | |
1457 | set_cpus_allowed_ptr(task, get_cpu_mask(gcwq->cpu)); | |
1458 | ||
1459 | spin_lock_irq(&gcwq->lock); | |
1460 | if (gcwq->flags & GCWQ_DISASSOCIATED) | |
1461 | return false; | |
1462 | if (task_cpu(task) == gcwq->cpu && | |
1463 | cpumask_equal(¤t->cpus_allowed, | |
1464 | get_cpu_mask(gcwq->cpu))) | |
1465 | return true; | |
1466 | spin_unlock_irq(&gcwq->lock); | |
1467 | ||
1468 | /* | |
1469 | * We've raced with CPU hot[un]plug. Give it a breather | |
1470 | * and retry migration. cond_resched() is required here; | |
1471 | * otherwise, we might deadlock against cpu_stop trying to | |
1472 | * bring down the CPU on non-preemptive kernel. | |
1473 | */ | |
1474 | cpu_relax(); | |
1475 | cond_resched(); | |
1476 | } | |
1477 | } | |
1478 | ||
1479 | struct idle_rebind { | |
1480 | int cnt; /* # workers to be rebound */ | |
1481 | struct completion done; /* all workers rebound */ | |
1482 | }; | |
1483 | ||
1484 | /* | |
1485 | * Rebind an idle @worker to its CPU. During CPU onlining, this has to | |
1486 | * happen synchronously for idle workers. worker_thread() will test | |
1487 | * %WORKER_REBIND before leaving idle and call this function. | |
1488 | */ | |
1489 | static void idle_worker_rebind(struct worker *worker) | |
1490 | { | |
1491 | struct global_cwq *gcwq = worker->pool->gcwq; | |
1492 | ||
1493 | /* CPU must be online at this point */ | |
1494 | WARN_ON(!worker_maybe_bind_and_lock(worker)); | |
1495 | if (!--worker->idle_rebind->cnt) | |
1496 | complete(&worker->idle_rebind->done); | |
1497 | spin_unlock_irq(&worker->pool->gcwq->lock); | |
1498 | ||
1499 | /* we did our part, wait for rebind_workers() to finish up */ | |
1500 | wait_event(gcwq->rebind_hold, !(worker->flags & WORKER_REBIND)); | |
1501 | } | |
1502 | ||
1503 | /* | |
1504 | * Function for @worker->rebind.work used to rebind unbound busy workers to | |
1505 | * the associated cpu which is coming back online. This is scheduled by | |
1506 | * cpu up but can race with other cpu hotplug operations and may be | |
1507 | * executed twice without intervening cpu down. | |
1508 | */ | |
1509 | static void busy_worker_rebind_fn(struct work_struct *work) | |
1510 | { | |
1511 | struct worker *worker = container_of(work, struct worker, rebind_work); | |
1512 | struct global_cwq *gcwq = worker->pool->gcwq; | |
1513 | ||
1514 | if (worker_maybe_bind_and_lock(worker)) | |
1515 | worker_clr_flags(worker, WORKER_REBIND); | |
1516 | ||
1517 | spin_unlock_irq(&gcwq->lock); | |
1518 | } | |
1519 | ||
1520 | /** | |
1521 | * rebind_workers - rebind all workers of a gcwq to the associated CPU | |
1522 | * @gcwq: gcwq of interest | |
1523 | * | |
1524 | * @gcwq->cpu is coming online. Rebind all workers to the CPU. Rebinding | |
1525 | * is different for idle and busy ones. | |
1526 | * | |
1527 | * The idle ones should be rebound synchronously and idle rebinding should | |
1528 | * be complete before any worker starts executing work items with | |
1529 | * concurrency management enabled; otherwise, scheduler may oops trying to | |
1530 | * wake up non-local idle worker from wq_worker_sleeping(). | |
1531 | * | |
1532 | * This is achieved by repeatedly requesting rebinding until all idle | |
1533 | * workers are known to have been rebound under @gcwq->lock and holding all | |
1534 | * idle workers from becoming busy until idle rebinding is complete. | |
1535 | * | |
1536 | * Once idle workers are rebound, busy workers can be rebound as they | |
1537 | * finish executing their current work items. Queueing the rebind work at | |
1538 | * the head of their scheduled lists is enough. Note that nr_running will | |
1539 | * be properbly bumped as busy workers rebind. | |
1540 | * | |
1541 | * On return, all workers are guaranteed to either be bound or have rebind | |
1542 | * work item scheduled. | |
1543 | */ | |
1544 | static void rebind_workers(struct global_cwq *gcwq) | |
1545 | __releases(&gcwq->lock) __acquires(&gcwq->lock) | |
1546 | { | |
1547 | struct idle_rebind idle_rebind; | |
1548 | struct worker_pool *pool; | |
1549 | struct worker *worker; | |
1550 | struct hlist_node *pos; | |
1551 | int i; | |
1552 | ||
1553 | lockdep_assert_held(&gcwq->lock); | |
1554 | ||
1555 | for_each_worker_pool(pool, gcwq) | |
1556 | lockdep_assert_held(&pool->manager_mutex); | |
1557 | ||
1558 | /* | |
1559 | * Rebind idle workers. Interlocked both ways. We wait for | |
1560 | * workers to rebind via @idle_rebind.done. Workers will wait for | |
1561 | * us to finish up by watching %WORKER_REBIND. | |
1562 | */ | |
1563 | init_completion(&idle_rebind.done); | |
1564 | retry: | |
1565 | idle_rebind.cnt = 1; | |
1566 | INIT_COMPLETION(idle_rebind.done); | |
1567 | ||
1568 | /* set REBIND and kick idle ones, we'll wait for these later */ | |
1569 | for_each_worker_pool(pool, gcwq) { | |
1570 | list_for_each_entry(worker, &pool->idle_list, entry) { | |
1571 | if (worker->flags & WORKER_REBIND) | |
1572 | continue; | |
1573 | ||
1574 | /* morph UNBOUND to REBIND */ | |
1575 | worker->flags &= ~WORKER_UNBOUND; | |
1576 | worker->flags |= WORKER_REBIND; | |
1577 | ||
1578 | idle_rebind.cnt++; | |
1579 | worker->idle_rebind = &idle_rebind; | |
1580 | ||
1581 | /* worker_thread() will call idle_worker_rebind() */ | |
1582 | wake_up_process(worker->task); | |
1583 | } | |
1584 | } | |
1585 | ||
1586 | if (--idle_rebind.cnt) { | |
1587 | spin_unlock_irq(&gcwq->lock); | |
1588 | wait_for_completion(&idle_rebind.done); | |
1589 | spin_lock_irq(&gcwq->lock); | |
1590 | /* busy ones might have become idle while waiting, retry */ | |
1591 | goto retry; | |
1592 | } | |
1593 | ||
1594 | /* | |
1595 | * All idle workers are rebound and waiting for %WORKER_REBIND to | |
1596 | * be cleared inside idle_worker_rebind(). Clear and release. | |
1597 | * Clearing %WORKER_REBIND from this foreign context is safe | |
1598 | * because these workers are still guaranteed to be idle. | |
1599 | */ | |
1600 | for_each_worker_pool(pool, gcwq) | |
1601 | list_for_each_entry(worker, &pool->idle_list, entry) | |
1602 | worker->flags &= ~WORKER_REBIND; | |
1603 | ||
1604 | wake_up_all(&gcwq->rebind_hold); | |
1605 | ||
1606 | /* rebind busy workers */ | |
1607 | for_each_busy_worker(worker, i, pos, gcwq) { | |
1608 | struct work_struct *rebind_work = &worker->rebind_work; | |
1609 | ||
1610 | /* morph UNBOUND to REBIND */ | |
1611 | worker->flags &= ~WORKER_UNBOUND; | |
1612 | worker->flags |= WORKER_REBIND; | |
1613 | ||
1614 | if (test_and_set_bit(WORK_STRUCT_PENDING_BIT, | |
1615 | work_data_bits(rebind_work))) | |
1616 | continue; | |
1617 | ||
1618 | /* wq doesn't matter, use the default one */ | |
1619 | debug_work_activate(rebind_work); | |
1620 | insert_work(get_cwq(gcwq->cpu, system_wq), rebind_work, | |
1621 | worker->scheduled.next, | |
1622 | work_color_to_flags(WORK_NO_COLOR)); | |
1623 | } | |
1624 | } | |
1625 | ||
1626 | static struct worker *alloc_worker(void) | |
1627 | { | |
1628 | struct worker *worker; | |
1629 | ||
1630 | worker = kzalloc(sizeof(*worker), GFP_KERNEL); | |
1631 | if (worker) { | |
1632 | INIT_LIST_HEAD(&worker->entry); | |
1633 | INIT_LIST_HEAD(&worker->scheduled); | |
1634 | INIT_WORK(&worker->rebind_work, busy_worker_rebind_fn); | |
1635 | /* on creation a worker is in !idle && prep state */ | |
1636 | worker->flags = WORKER_PREP; | |
1637 | } | |
1638 | return worker; | |
1639 | } | |
1640 | ||
1641 | /** | |
1642 | * create_worker - create a new workqueue worker | |
1643 | * @pool: pool the new worker will belong to | |
1644 | * | |
1645 | * Create a new worker which is bound to @pool. The returned worker | |
1646 | * can be started by calling start_worker() or destroyed using | |
1647 | * destroy_worker(). | |
1648 | * | |
1649 | * CONTEXT: | |
1650 | * Might sleep. Does GFP_KERNEL allocations. | |
1651 | * | |
1652 | * RETURNS: | |
1653 | * Pointer to the newly created worker. | |
1654 | */ | |
1655 | static struct worker *create_worker(struct worker_pool *pool) | |
1656 | { | |
1657 | struct global_cwq *gcwq = pool->gcwq; | |
1658 | const char *pri = worker_pool_pri(pool) ? "H" : ""; | |
1659 | struct worker *worker = NULL; | |
1660 | int id = -1; | |
1661 | ||
1662 | spin_lock_irq(&gcwq->lock); | |
1663 | while (ida_get_new(&pool->worker_ida, &id)) { | |
1664 | spin_unlock_irq(&gcwq->lock); | |
1665 | if (!ida_pre_get(&pool->worker_ida, GFP_KERNEL)) | |
1666 | goto fail; | |
1667 | spin_lock_irq(&gcwq->lock); | |
1668 | } | |
1669 | spin_unlock_irq(&gcwq->lock); | |
1670 | ||
1671 | worker = alloc_worker(); | |
1672 | if (!worker) | |
1673 | goto fail; | |
1674 | ||
1675 | worker->pool = pool; | |
1676 | worker->id = id; | |
1677 | ||
1678 | if (gcwq->cpu != WORK_CPU_UNBOUND) | |
1679 | worker->task = kthread_create_on_node(worker_thread, | |
1680 | worker, cpu_to_node(gcwq->cpu), | |
1681 | "kworker/%u:%d%s", gcwq->cpu, id, pri); | |
1682 | else | |
1683 | worker->task = kthread_create(worker_thread, worker, | |
1684 | "kworker/u:%d%s", id, pri); | |
1685 | if (IS_ERR(worker->task)) | |
1686 | goto fail; | |
1687 | ||
1688 | if (worker_pool_pri(pool)) | |
1689 | set_user_nice(worker->task, HIGHPRI_NICE_LEVEL); | |
1690 | ||
1691 | /* | |
1692 | * Determine CPU binding of the new worker depending on | |
1693 | * %GCWQ_DISASSOCIATED. The caller is responsible for ensuring the | |
1694 | * flag remains stable across this function. See the comments | |
1695 | * above the flag definition for details. | |
1696 | * | |
1697 | * As an unbound worker may later become a regular one if CPU comes | |
1698 | * online, make sure every worker has %PF_THREAD_BOUND set. | |
1699 | */ | |
1700 | if (!(gcwq->flags & GCWQ_DISASSOCIATED)) { | |
1701 | kthread_bind(worker->task, gcwq->cpu); | |
1702 | } else { | |
1703 | worker->task->flags |= PF_THREAD_BOUND; | |
1704 | worker->flags |= WORKER_UNBOUND; | |
1705 | } | |
1706 | ||
1707 | return worker; | |
1708 | fail: | |
1709 | if (id >= 0) { | |
1710 | spin_lock_irq(&gcwq->lock); | |
1711 | ida_remove(&pool->worker_ida, id); | |
1712 | spin_unlock_irq(&gcwq->lock); | |
1713 | } | |
1714 | kfree(worker); | |
1715 | return NULL; | |
1716 | } | |
1717 | ||
1718 | /** | |
1719 | * start_worker - start a newly created worker | |
1720 | * @worker: worker to start | |
1721 | * | |
1722 | * Make the gcwq aware of @worker and start it. | |
1723 | * | |
1724 | * CONTEXT: | |
1725 | * spin_lock_irq(gcwq->lock). | |
1726 | */ | |
1727 | static void start_worker(struct worker *worker) | |
1728 | { | |
1729 | worker->flags |= WORKER_STARTED; | |
1730 | worker->pool->nr_workers++; | |
1731 | worker_enter_idle(worker); | |
1732 | wake_up_process(worker->task); | |
1733 | } | |
1734 | ||
1735 | /** | |
1736 | * destroy_worker - destroy a workqueue worker | |
1737 | * @worker: worker to be destroyed | |
1738 | * | |
1739 | * Destroy @worker and adjust @gcwq stats accordingly. | |
1740 | * | |
1741 | * CONTEXT: | |
1742 | * spin_lock_irq(gcwq->lock) which is released and regrabbed. | |
1743 | */ | |
1744 | static void destroy_worker(struct worker *worker) | |
1745 | { | |
1746 | struct worker_pool *pool = worker->pool; | |
1747 | struct global_cwq *gcwq = pool->gcwq; | |
1748 | int id = worker->id; | |
1749 | ||
1750 | /* sanity check frenzy */ | |
1751 | BUG_ON(worker->current_work); | |
1752 | BUG_ON(!list_empty(&worker->scheduled)); | |
1753 | ||
1754 | if (worker->flags & WORKER_STARTED) | |
1755 | pool->nr_workers--; | |
1756 | if (worker->flags & WORKER_IDLE) | |
1757 | pool->nr_idle--; | |
1758 | ||
1759 | list_del_init(&worker->entry); | |
1760 | worker->flags |= WORKER_DIE; | |
1761 | ||
1762 | spin_unlock_irq(&gcwq->lock); | |
1763 | ||
1764 | kthread_stop(worker->task); | |
1765 | kfree(worker); | |
1766 | ||
1767 | spin_lock_irq(&gcwq->lock); | |
1768 | ida_remove(&pool->worker_ida, id); | |
1769 | } | |
1770 | ||
1771 | static void idle_worker_timeout(unsigned long __pool) | |
1772 | { | |
1773 | struct worker_pool *pool = (void *)__pool; | |
1774 | struct global_cwq *gcwq = pool->gcwq; | |
1775 | ||
1776 | spin_lock_irq(&gcwq->lock); | |
1777 | ||
1778 | if (too_many_workers(pool)) { | |
1779 | struct worker *worker; | |
1780 | unsigned long expires; | |
1781 | ||
1782 | /* idle_list is kept in LIFO order, check the last one */ | |
1783 | worker = list_entry(pool->idle_list.prev, struct worker, entry); | |
1784 | expires = worker->last_active + IDLE_WORKER_TIMEOUT; | |
1785 | ||
1786 | if (time_before(jiffies, expires)) | |
1787 | mod_timer(&pool->idle_timer, expires); | |
1788 | else { | |
1789 | /* it's been idle for too long, wake up manager */ | |
1790 | pool->flags |= POOL_MANAGE_WORKERS; | |
1791 | wake_up_worker(pool); | |
1792 | } | |
1793 | } | |
1794 | ||
1795 | spin_unlock_irq(&gcwq->lock); | |
1796 | } | |
1797 | ||
1798 | static bool send_mayday(struct work_struct *work) | |
1799 | { | |
1800 | struct cpu_workqueue_struct *cwq = get_work_cwq(work); | |
1801 | struct workqueue_struct *wq = cwq->wq; | |
1802 | unsigned int cpu; | |
1803 | ||
1804 | if (!(wq->flags & WQ_RESCUER)) | |
1805 | return false; | |
1806 | ||
1807 | /* mayday mayday mayday */ | |
1808 | cpu = cwq->pool->gcwq->cpu; | |
1809 | /* WORK_CPU_UNBOUND can't be set in cpumask, use cpu 0 instead */ | |
1810 | if (cpu == WORK_CPU_UNBOUND) | |
1811 | cpu = 0; | |
1812 | if (!mayday_test_and_set_cpu(cpu, wq->mayday_mask)) | |
1813 | wake_up_process(wq->rescuer->task); | |
1814 | return true; | |
1815 | } | |
1816 | ||
1817 | static void gcwq_mayday_timeout(unsigned long __pool) | |
1818 | { | |
1819 | struct worker_pool *pool = (void *)__pool; | |
1820 | struct global_cwq *gcwq = pool->gcwq; | |
1821 | struct work_struct *work; | |
1822 | ||
1823 | spin_lock_irq(&gcwq->lock); | |
1824 | ||
1825 | if (need_to_create_worker(pool)) { | |
1826 | /* | |
1827 | * We've been trying to create a new worker but | |
1828 | * haven't been successful. We might be hitting an | |
1829 | * allocation deadlock. Send distress signals to | |
1830 | * rescuers. | |
1831 | */ | |
1832 | list_for_each_entry(work, &pool->worklist, entry) | |
1833 | send_mayday(work); | |
1834 | } | |
1835 | ||
1836 | spin_unlock_irq(&gcwq->lock); | |
1837 | ||
1838 | mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INTERVAL); | |
1839 | } | |
1840 | ||
1841 | /** | |
1842 | * maybe_create_worker - create a new worker if necessary | |
1843 | * @pool: pool to create a new worker for | |
1844 | * | |
1845 | * Create a new worker for @pool if necessary. @pool is guaranteed to | |
1846 | * have at least one idle worker on return from this function. If | |
1847 | * creating a new worker takes longer than MAYDAY_INTERVAL, mayday is | |
1848 | * sent to all rescuers with works scheduled on @pool to resolve | |
1849 | * possible allocation deadlock. | |
1850 | * | |
1851 | * On return, need_to_create_worker() is guaranteed to be false and | |
1852 | * may_start_working() true. | |
1853 | * | |
1854 | * LOCKING: | |
1855 | * spin_lock_irq(gcwq->lock) which may be released and regrabbed | |
1856 | * multiple times. Does GFP_KERNEL allocations. Called only from | |
1857 | * manager. | |
1858 | * | |
1859 | * RETURNS: | |
1860 | * false if no action was taken and gcwq->lock stayed locked, true | |
1861 | * otherwise. | |
1862 | */ | |
1863 | static bool maybe_create_worker(struct worker_pool *pool) | |
1864 | __releases(&gcwq->lock) | |
1865 | __acquires(&gcwq->lock) | |
1866 | { | |
1867 | struct global_cwq *gcwq = pool->gcwq; | |
1868 | ||
1869 | if (!need_to_create_worker(pool)) | |
1870 | return false; | |
1871 | restart: | |
1872 | spin_unlock_irq(&gcwq->lock); | |
1873 | ||
1874 | /* if we don't make progress in MAYDAY_INITIAL_TIMEOUT, call for help */ | |
1875 | mod_timer(&pool->mayday_timer, jiffies + MAYDAY_INITIAL_TIMEOUT); | |
1876 | ||
1877 | while (true) { | |
1878 | struct worker *worker; | |
1879 | ||
1880 | worker = create_worker(pool); | |
1881 | if (worker) { | |
1882 | del_timer_sync(&pool->mayday_timer); | |
1883 | spin_lock_irq(&gcwq->lock); | |
1884 | start_worker(worker); | |
1885 | BUG_ON(need_to_create_worker(pool)); | |
1886 | return true; | |
1887 | } | |
1888 | ||
1889 | if (!need_to_create_worker(pool)) | |
1890 | break; | |
1891 | ||
1892 | __set_current_state(TASK_INTERRUPTIBLE); | |
1893 | schedule_timeout(CREATE_COOLDOWN); | |
1894 | ||
1895 | if (!need_to_create_worker(pool)) | |
1896 | break; | |
1897 | } | |
1898 | ||
1899 | del_timer_sync(&pool->mayday_timer); | |
1900 | spin_lock_irq(&gcwq->lock); | |
1901 | if (need_to_create_worker(pool)) | |
1902 | goto restart; | |
1903 | return true; | |
1904 | } | |
1905 | ||
1906 | /** | |
1907 | * maybe_destroy_worker - destroy workers which have been idle for a while | |
1908 | * @pool: pool to destroy workers for | |
1909 | * | |
1910 | * Destroy @pool workers which have been idle for longer than | |
1911 | * IDLE_WORKER_TIMEOUT. | |
1912 | * | |
1913 | * LOCKING: | |
1914 | * spin_lock_irq(gcwq->lock) which may be released and regrabbed | |
1915 | * multiple times. Called only from manager. | |
1916 | * | |
1917 | * RETURNS: | |
1918 | * false if no action was taken and gcwq->lock stayed locked, true | |
1919 | * otherwise. | |
1920 | */ | |
1921 | static bool maybe_destroy_workers(struct worker_pool *pool) | |
1922 | { | |
1923 | bool ret = false; | |
1924 | ||
1925 | while (too_many_workers(pool)) { | |
1926 | struct worker *worker; | |
1927 | unsigned long expires; | |
1928 | ||
1929 | worker = list_entry(pool->idle_list.prev, struct worker, entry); | |
1930 | expires = worker->last_active + IDLE_WORKER_TIMEOUT; | |
1931 | ||
1932 | if (time_before(jiffies, expires)) { | |
1933 | mod_timer(&pool->idle_timer, expires); | |
1934 | break; | |
1935 | } | |
1936 | ||
1937 | destroy_worker(worker); | |
1938 | ret = true; | |
1939 | } | |
1940 | ||
1941 | return ret; | |
1942 | } | |
1943 | ||
1944 | /** | |
1945 | * manage_workers - manage worker pool | |
1946 | * @worker: self | |
1947 | * | |
1948 | * Assume the manager role and manage gcwq worker pool @worker belongs | |
1949 | * to. At any given time, there can be only zero or one manager per | |
1950 | * gcwq. The exclusion is handled automatically by this function. | |
1951 | * | |
1952 | * The caller can safely start processing works on false return. On | |
1953 | * true return, it's guaranteed that need_to_create_worker() is false | |
1954 | * and may_start_working() is true. | |
1955 | * | |
1956 | * CONTEXT: | |
1957 | * spin_lock_irq(gcwq->lock) which may be released and regrabbed | |
1958 | * multiple times. Does GFP_KERNEL allocations. | |
1959 | * | |
1960 | * RETURNS: | |
1961 | * false if no action was taken and gcwq->lock stayed locked, true if | |
1962 | * some action was taken. | |
1963 | */ | |
1964 | static bool manage_workers(struct worker *worker) | |
1965 | { | |
1966 | struct worker_pool *pool = worker->pool; | |
1967 | bool ret = false; | |
1968 | ||
1969 | if (!mutex_trylock(&pool->manager_mutex)) | |
1970 | return ret; | |
1971 | ||
1972 | pool->flags &= ~POOL_MANAGE_WORKERS; | |
1973 | ||
1974 | /* | |
1975 | * Destroy and then create so that may_start_working() is true | |
1976 | * on return. | |
1977 | */ | |
1978 | ret |= maybe_destroy_workers(pool); | |
1979 | ret |= maybe_create_worker(pool); | |
1980 | ||
1981 | mutex_unlock(&pool->manager_mutex); | |
1982 | return ret; | |
1983 | } | |
1984 | ||
1985 | /** | |
1986 | * process_one_work - process single work | |
1987 | * @worker: self | |
1988 | * @work: work to process | |
1989 | * | |
1990 | * Process @work. This function contains all the logics necessary to | |
1991 | * process a single work including synchronization against and | |
1992 | * interaction with other workers on the same cpu, queueing and | |
1993 | * flushing. As long as context requirement is met, any worker can | |
1994 | * call this function to process a work. | |
1995 | * | |
1996 | * CONTEXT: | |
1997 | * spin_lock_irq(gcwq->lock) which is released and regrabbed. | |
1998 | */ | |
1999 | static void process_one_work(struct worker *worker, struct work_struct *work) | |
2000 | __releases(&gcwq->lock) | |
2001 | __acquires(&gcwq->lock) | |
2002 | { | |
2003 | struct cpu_workqueue_struct *cwq = get_work_cwq(work); | |
2004 | struct worker_pool *pool = worker->pool; | |
2005 | struct global_cwq *gcwq = pool->gcwq; | |
2006 | struct hlist_head *bwh = busy_worker_head(gcwq, work); | |
2007 | bool cpu_intensive = cwq->wq->flags & WQ_CPU_INTENSIVE; | |
2008 | work_func_t f = work->func; | |
2009 | int work_color; | |
2010 | struct worker *collision; | |
2011 | #ifdef CONFIG_LOCKDEP | |
2012 | /* | |
2013 | * It is permissible to free the struct work_struct from | |
2014 | * inside the function that is called from it, this we need to | |
2015 | * take into account for lockdep too. To avoid bogus "held | |
2016 | * lock freed" warnings as well as problems when looking into | |
2017 | * work->lockdep_map, make a copy and use that here. | |
2018 | */ | |
2019 | struct lockdep_map lockdep_map; | |
2020 | ||
2021 | lockdep_copy_map(&lockdep_map, &work->lockdep_map); | |
2022 | #endif | |
2023 | /* | |
2024 | * Ensure we're on the correct CPU. DISASSOCIATED test is | |
2025 | * necessary to avoid spurious warnings from rescuers servicing the | |
2026 | * unbound or a disassociated gcwq. | |
2027 | */ | |
2028 | WARN_ON_ONCE(!(worker->flags & (WORKER_UNBOUND | WORKER_REBIND)) && | |
2029 | !(gcwq->flags & GCWQ_DISASSOCIATED) && | |
2030 | raw_smp_processor_id() != gcwq->cpu); | |
2031 | ||
2032 | /* | |
2033 | * A single work shouldn't be executed concurrently by | |
2034 | * multiple workers on a single cpu. Check whether anyone is | |
2035 | * already processing the work. If so, defer the work to the | |
2036 | * currently executing one. | |
2037 | */ | |
2038 | collision = __find_worker_executing_work(gcwq, bwh, work); | |
2039 | if (unlikely(collision)) { | |
2040 | move_linked_works(work, &collision->scheduled, NULL); | |
2041 | return; | |
2042 | } | |
2043 | ||
2044 | /* claim and dequeue */ | |
2045 | debug_work_deactivate(work); | |
2046 | hlist_add_head(&worker->hentry, bwh); | |
2047 | worker->current_work = work; | |
2048 | worker->current_cwq = cwq; | |
2049 | work_color = get_work_color(work); | |
2050 | ||
2051 | list_del_init(&work->entry); | |
2052 | ||
2053 | /* | |
2054 | * CPU intensive works don't participate in concurrency | |
2055 | * management. They're the scheduler's responsibility. | |
2056 | */ | |
2057 | if (unlikely(cpu_intensive)) | |
2058 | worker_set_flags(worker, WORKER_CPU_INTENSIVE, true); | |
2059 | ||
2060 | /* | |
2061 | * Unbound gcwq isn't concurrency managed and work items should be | |
2062 | * executed ASAP. Wake up another worker if necessary. | |
2063 | */ | |
2064 | if ((worker->flags & WORKER_UNBOUND) && need_more_worker(pool)) | |
2065 | wake_up_worker(pool); | |
2066 | ||
2067 | /* | |
2068 | * Record the last CPU and clear PENDING. The following wmb is | |
2069 | * paired with the implied mb in test_and_set_bit(PENDING) and | |
2070 | * ensures all updates to @work made here are visible to and | |
2071 | * precede any updates by the next PENDING owner. Also, clear | |
2072 | * PENDING inside @gcwq->lock so that PENDING and queued state | |
2073 | * changes happen together while IRQ is disabled. | |
2074 | */ | |
2075 | smp_wmb(); | |
2076 | set_work_cpu_and_clear_pending(work, gcwq->cpu); | |
2077 | ||
2078 | spin_unlock_irq(&gcwq->lock); | |
2079 | ||
2080 | lock_map_acquire_read(&cwq->wq->lockdep_map); | |
2081 | lock_map_acquire(&lockdep_map); | |
2082 | trace_workqueue_execute_start(work); | |
2083 | f(work); | |
2084 | /* | |
2085 | * While we must be careful to not use "work" after this, the trace | |
2086 | * point will only record its address. | |
2087 | */ | |
2088 | trace_workqueue_execute_end(work); | |
2089 | lock_map_release(&lockdep_map); | |
2090 | lock_map_release(&cwq->wq->lockdep_map); | |
2091 | ||
2092 | if (unlikely(in_atomic() || lockdep_depth(current) > 0)) { | |
2093 | printk(KERN_ERR "BUG: workqueue leaked lock or atomic: " | |
2094 | "%s/0x%08x/%d\n", | |
2095 | current->comm, preempt_count(), task_pid_nr(current)); | |
2096 | printk(KERN_ERR " last function: "); | |
2097 | print_symbol("%s\n", (unsigned long)f); | |
2098 | debug_show_held_locks(current); | |
2099 | dump_stack(); | |
2100 | } | |
2101 | ||
2102 | spin_lock_irq(&gcwq->lock); | |
2103 | ||
2104 | /* clear cpu intensive status */ | |
2105 | if (unlikely(cpu_intensive)) | |
2106 | worker_clr_flags(worker, WORKER_CPU_INTENSIVE); | |
2107 | ||
2108 | /* we're done with it, release */ | |
2109 | hlist_del_init(&worker->hentry); | |
2110 | worker->current_work = NULL; | |
2111 | worker->current_cwq = NULL; | |
2112 | cwq_dec_nr_in_flight(cwq, work_color, false); | |
2113 | } | |
2114 | ||
2115 | /** | |
2116 | * process_scheduled_works - process scheduled works | |
2117 | * @worker: self | |
2118 | * | |
2119 | * Process all scheduled works. Please note that the scheduled list | |
2120 | * may change while processing a work, so this function repeatedly | |
2121 | * fetches a work from the top and executes it. | |
2122 | * | |
2123 | * CONTEXT: | |
2124 | * spin_lock_irq(gcwq->lock) which may be released and regrabbed | |
2125 | * multiple times. | |
2126 | */ | |
2127 | static void process_scheduled_works(struct worker *worker) | |
2128 | { | |
2129 | while (!list_empty(&worker->scheduled)) { | |
2130 | struct work_struct *work = list_first_entry(&worker->scheduled, | |
2131 | struct work_struct, entry); | |
2132 | process_one_work(worker, work); | |
2133 | } | |
2134 | } | |
2135 | ||
2136 | /** | |
2137 | * worker_thread - the worker thread function | |
2138 | * @__worker: self | |
2139 | * | |
2140 | * The gcwq worker thread function. There's a single dynamic pool of | |
2141 | * these per each cpu. These workers process all works regardless of | |
2142 | * their specific target workqueue. The only exception is works which | |
2143 | * belong to workqueues with a rescuer which will be explained in | |
2144 | * rescuer_thread(). | |
2145 | */ | |
2146 | static int worker_thread(void *__worker) | |
2147 | { | |
2148 | struct worker *worker = __worker; | |
2149 | struct worker_pool *pool = worker->pool; | |
2150 | struct global_cwq *gcwq = pool->gcwq; | |
2151 | ||
2152 | /* tell the scheduler that this is a workqueue worker */ | |
2153 | worker->task->flags |= PF_WQ_WORKER; | |
2154 | woke_up: | |
2155 | spin_lock_irq(&gcwq->lock); | |
2156 | ||
2157 | /* | |
2158 | * DIE can be set only while idle and REBIND set while busy has | |
2159 | * @worker->rebind_work scheduled. Checking here is enough. | |
2160 | */ | |
2161 | if (unlikely(worker->flags & (WORKER_REBIND | WORKER_DIE))) { | |
2162 | spin_unlock_irq(&gcwq->lock); | |
2163 | ||
2164 | if (worker->flags & WORKER_DIE) { | |
2165 | worker->task->flags &= ~PF_WQ_WORKER; | |
2166 | return 0; | |
2167 | } | |
2168 | ||
2169 | idle_worker_rebind(worker); | |
2170 | goto woke_up; | |
2171 | } | |
2172 | ||
2173 | worker_leave_idle(worker); | |
2174 | recheck: | |
2175 | /* no more worker necessary? */ | |
2176 | if (!need_more_worker(pool)) | |
2177 | goto sleep; | |
2178 | ||
2179 | /* do we need to manage? */ | |
2180 | if (unlikely(!may_start_working(pool)) && manage_workers(worker)) | |
2181 | goto recheck; | |
2182 | ||
2183 | /* | |
2184 | * ->scheduled list can only be filled while a worker is | |
2185 | * preparing to process a work or actually processing it. | |
2186 | * Make sure nobody diddled with it while I was sleeping. | |
2187 | */ | |
2188 | BUG_ON(!list_empty(&worker->scheduled)); | |
2189 | ||
2190 | /* | |
2191 | * When control reaches this point, we're guaranteed to have | |
2192 | * at least one idle worker or that someone else has already | |
2193 | * assumed the manager role. | |
2194 | */ | |
2195 | worker_clr_flags(worker, WORKER_PREP); | |
2196 | ||
2197 | do { | |
2198 | struct work_struct *work = | |
2199 | list_first_entry(&pool->worklist, | |
2200 | struct work_struct, entry); | |
2201 | ||
2202 | if (likely(!(*work_data_bits(work) & WORK_STRUCT_LINKED))) { | |
2203 | /* optimization path, not strictly necessary */ | |
2204 | process_one_work(worker, work); | |
2205 | if (unlikely(!list_empty(&worker->scheduled))) | |
2206 | process_scheduled_works(worker); | |
2207 | } else { | |
2208 | move_linked_works(work, &worker->scheduled, NULL); | |
2209 | process_scheduled_works(worker); | |
2210 | } | |
2211 | } while (keep_working(pool)); | |
2212 | ||
2213 | worker_set_flags(worker, WORKER_PREP, false); | |
2214 | sleep: | |
2215 | if (unlikely(need_to_manage_workers(pool)) && manage_workers(worker)) | |
2216 | goto recheck; | |
2217 | ||
2218 | /* | |
2219 | * gcwq->lock is held and there's no work to process and no | |
2220 | * need to manage, sleep. Workers are woken up only while | |
2221 | * holding gcwq->lock or from local cpu, so setting the | |
2222 | * current state before releasing gcwq->lock is enough to | |
2223 | * prevent losing any event. | |
2224 | */ | |
2225 | worker_enter_idle(worker); | |
2226 | __set_current_state(TASK_INTERRUPTIBLE); | |
2227 | spin_unlock_irq(&gcwq->lock); | |
2228 | schedule(); | |
2229 | goto woke_up; | |
2230 | } | |
2231 | ||
2232 | /** | |
2233 | * rescuer_thread - the rescuer thread function | |
2234 | * @__wq: the associated workqueue | |
2235 | * | |
2236 | * Workqueue rescuer thread function. There's one rescuer for each | |
2237 | * workqueue which has WQ_RESCUER set. | |
2238 | * | |
2239 | * Regular work processing on a gcwq may block trying to create a new | |
2240 | * worker which uses GFP_KERNEL allocation which has slight chance of | |
2241 | * developing into deadlock if some works currently on the same queue | |
2242 | * need to be processed to satisfy the GFP_KERNEL allocation. This is | |
2243 | * the problem rescuer solves. | |
2244 | * | |
2245 | * When such condition is possible, the gcwq summons rescuers of all | |
2246 | * workqueues which have works queued on the gcwq and let them process | |
2247 | * those works so that forward progress can be guaranteed. | |
2248 | * | |
2249 | * This should happen rarely. | |
2250 | */ | |
2251 | static int rescuer_thread(void *__wq) | |
2252 | { | |
2253 | struct workqueue_struct *wq = __wq; | |
2254 | struct worker *rescuer = wq->rescuer; | |
2255 | struct list_head *scheduled = &rescuer->scheduled; | |
2256 | bool is_unbound = wq->flags & WQ_UNBOUND; | |
2257 | unsigned int cpu; | |
2258 | ||
2259 | set_user_nice(current, RESCUER_NICE_LEVEL); | |
2260 | repeat: | |
2261 | set_current_state(TASK_INTERRUPTIBLE); | |
2262 | ||
2263 | if (kthread_should_stop()) | |
2264 | return 0; | |
2265 | ||
2266 | /* | |
2267 | * See whether any cpu is asking for help. Unbounded | |
2268 | * workqueues use cpu 0 in mayday_mask for CPU_UNBOUND. | |
2269 | */ | |
2270 | for_each_mayday_cpu(cpu, wq->mayday_mask) { | |
2271 | unsigned int tcpu = is_unbound ? WORK_CPU_UNBOUND : cpu; | |
2272 | struct cpu_workqueue_struct *cwq = get_cwq(tcpu, wq); | |
2273 | struct worker_pool *pool = cwq->pool; | |
2274 | struct global_cwq *gcwq = pool->gcwq; | |
2275 | struct work_struct *work, *n; | |
2276 | ||
2277 | __set_current_state(TASK_RUNNING); | |
2278 | mayday_clear_cpu(cpu, wq->mayday_mask); | |
2279 | ||
2280 | /* migrate to the target cpu if possible */ | |
2281 | rescuer->pool = pool; | |
2282 | worker_maybe_bind_and_lock(rescuer); | |
2283 | ||
2284 | /* | |
2285 | * Slurp in all works issued via this workqueue and | |
2286 | * process'em. | |
2287 | */ | |
2288 | BUG_ON(!list_empty(&rescuer->scheduled)); | |
2289 | list_for_each_entry_safe(work, n, &pool->worklist, entry) | |
2290 | if (get_work_cwq(work) == cwq) | |
2291 | move_linked_works(work, scheduled, &n); | |
2292 | ||
2293 | process_scheduled_works(rescuer); | |
2294 | ||
2295 | /* | |
2296 | * Leave this gcwq. If keep_working() is %true, notify a | |
2297 | * regular worker; otherwise, we end up with 0 concurrency | |
2298 | * and stalling the execution. | |
2299 | */ | |
2300 | if (keep_working(pool)) | |
2301 | wake_up_worker(pool); | |
2302 | ||
2303 | spin_unlock_irq(&gcwq->lock); | |
2304 | } | |
2305 | ||
2306 | schedule(); | |
2307 | goto repeat; | |
2308 | } | |
2309 | ||
2310 | struct wq_barrier { | |
2311 | struct work_struct work; | |
2312 | struct completion done; | |
2313 | }; | |
2314 | ||
2315 | static void wq_barrier_func(struct work_struct *work) | |
2316 | { | |
2317 | struct wq_barrier *barr = container_of(work, struct wq_barrier, work); | |
2318 | complete(&barr->done); | |
2319 | } | |
2320 | ||
2321 | /** | |
2322 | * insert_wq_barrier - insert a barrier work | |
2323 | * @cwq: cwq to insert barrier into | |
2324 | * @barr: wq_barrier to insert | |
2325 | * @target: target work to attach @barr to | |
2326 | * @worker: worker currently executing @target, NULL if @target is not executing | |
2327 | * | |
2328 | * @barr is linked to @target such that @barr is completed only after | |
2329 | * @target finishes execution. Please note that the ordering | |
2330 | * guarantee is observed only with respect to @target and on the local | |
2331 | * cpu. | |
2332 | * | |
2333 | * Currently, a queued barrier can't be canceled. This is because | |
2334 | * try_to_grab_pending() can't determine whether the work to be | |
2335 | * grabbed is at the head of the queue and thus can't clear LINKED | |
2336 | * flag of the previous work while there must be a valid next work | |
2337 | * after a work with LINKED flag set. | |
2338 | * | |
2339 | * Note that when @worker is non-NULL, @target may be modified | |
2340 | * underneath us, so we can't reliably determine cwq from @target. | |
2341 | * | |
2342 | * CONTEXT: | |
2343 | * spin_lock_irq(gcwq->lock). | |
2344 | */ | |
2345 | static void insert_wq_barrier(struct cpu_workqueue_struct *cwq, | |
2346 | struct wq_barrier *barr, | |
2347 | struct work_struct *target, struct worker *worker) | |
2348 | { | |
2349 | struct list_head *head; | |
2350 | unsigned int linked = 0; | |
2351 | ||
2352 | /* | |
2353 | * debugobject calls are safe here even with gcwq->lock locked | |
2354 | * as we know for sure that this will not trigger any of the | |
2355 | * checks and call back into the fixup functions where we | |
2356 | * might deadlock. | |
2357 | */ | |
2358 | INIT_WORK_ONSTACK(&barr->work, wq_barrier_func); | |
2359 | __set_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(&barr->work)); | |
2360 | init_completion(&barr->done); | |
2361 | ||
2362 | /* | |
2363 | * If @target is currently being executed, schedule the | |
2364 | * barrier to the worker; otherwise, put it after @target. | |
2365 | */ | |
2366 | if (worker) | |
2367 | head = worker->scheduled.next; | |
2368 | else { | |
2369 | unsigned long *bits = work_data_bits(target); | |
2370 | ||
2371 | head = target->entry.next; | |
2372 | /* there can already be other linked works, inherit and set */ | |
2373 | linked = *bits & WORK_STRUCT_LINKED; | |
2374 | __set_bit(WORK_STRUCT_LINKED_BIT, bits); | |
2375 | } | |
2376 | ||
2377 | debug_work_activate(&barr->work); | |
2378 | insert_work(cwq, &barr->work, head, | |
2379 | work_color_to_flags(WORK_NO_COLOR) | linked); | |
2380 | } | |
2381 | ||
2382 | /** | |
2383 | * flush_workqueue_prep_cwqs - prepare cwqs for workqueue flushing | |
2384 | * @wq: workqueue being flushed | |
2385 | * @flush_color: new flush color, < 0 for no-op | |
2386 | * @work_color: new work color, < 0 for no-op | |
2387 | * | |
2388 | * Prepare cwqs for workqueue flushing. | |
2389 | * | |
2390 | * If @flush_color is non-negative, flush_color on all cwqs should be | |
2391 | * -1. If no cwq has in-flight commands at the specified color, all | |
2392 | * cwq->flush_color's stay at -1 and %false is returned. If any cwq | |
2393 | * has in flight commands, its cwq->flush_color is set to | |
2394 | * @flush_color, @wq->nr_cwqs_to_flush is updated accordingly, cwq | |
2395 | * wakeup logic is armed and %true is returned. | |
2396 | * | |
2397 | * The caller should have initialized @wq->first_flusher prior to | |
2398 | * calling this function with non-negative @flush_color. If | |
2399 | * @flush_color is negative, no flush color update is done and %false | |
2400 | * is returned. | |
2401 | * | |
2402 | * If @work_color is non-negative, all cwqs should have the same | |
2403 | * work_color which is previous to @work_color and all will be | |
2404 | * advanced to @work_color. | |
2405 | * | |
2406 | * CONTEXT: | |
2407 | * mutex_lock(wq->flush_mutex). | |
2408 | * | |
2409 | * RETURNS: | |
2410 | * %true if @flush_color >= 0 and there's something to flush. %false | |
2411 | * otherwise. | |
2412 | */ | |
2413 | static bool flush_workqueue_prep_cwqs(struct workqueue_struct *wq, | |
2414 | int flush_color, int work_color) | |
2415 | { | |
2416 | bool wait = false; | |
2417 | unsigned int cpu; | |
2418 | ||
2419 | if (flush_color >= 0) { | |
2420 | BUG_ON(atomic_read(&wq->nr_cwqs_to_flush)); | |
2421 | atomic_set(&wq->nr_cwqs_to_flush, 1); | |
2422 | } | |
2423 | ||
2424 | for_each_cwq_cpu(cpu, wq) { | |
2425 | struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); | |
2426 | struct global_cwq *gcwq = cwq->pool->gcwq; | |
2427 | ||
2428 | spin_lock_irq(&gcwq->lock); | |
2429 | ||
2430 | if (flush_color >= 0) { | |
2431 | BUG_ON(cwq->flush_color != -1); | |
2432 | ||
2433 | if (cwq->nr_in_flight[flush_color]) { | |
2434 | cwq->flush_color = flush_color; | |
2435 | atomic_inc(&wq->nr_cwqs_to_flush); | |
2436 | wait = true; | |
2437 | } | |
2438 | } | |
2439 | ||
2440 | if (work_color >= 0) { | |
2441 | BUG_ON(work_color != work_next_color(cwq->work_color)); | |
2442 | cwq->work_color = work_color; | |
2443 | } | |
2444 | ||
2445 | spin_unlock_irq(&gcwq->lock); | |
2446 | } | |
2447 | ||
2448 | if (flush_color >= 0 && atomic_dec_and_test(&wq->nr_cwqs_to_flush)) | |
2449 | complete(&wq->first_flusher->done); | |
2450 | ||
2451 | return wait; | |
2452 | } | |
2453 | ||
2454 | /** | |
2455 | * flush_workqueue - ensure that any scheduled work has run to completion. | |
2456 | * @wq: workqueue to flush | |
2457 | * | |
2458 | * Forces execution of the workqueue and blocks until its completion. | |
2459 | * This is typically used in driver shutdown handlers. | |
2460 | * | |
2461 | * We sleep until all works which were queued on entry have been handled, | |
2462 | * but we are not livelocked by new incoming ones. | |
2463 | */ | |
2464 | void flush_workqueue(struct workqueue_struct *wq) | |
2465 | { | |
2466 | struct wq_flusher this_flusher = { | |
2467 | .list = LIST_HEAD_INIT(this_flusher.list), | |
2468 | .flush_color = -1, | |
2469 | .done = COMPLETION_INITIALIZER_ONSTACK(this_flusher.done), | |
2470 | }; | |
2471 | int next_color; | |
2472 | ||
2473 | lock_map_acquire(&wq->lockdep_map); | |
2474 | lock_map_release(&wq->lockdep_map); | |
2475 | ||
2476 | mutex_lock(&wq->flush_mutex); | |
2477 | ||
2478 | /* | |
2479 | * Start-to-wait phase | |
2480 | */ | |
2481 | next_color = work_next_color(wq->work_color); | |
2482 | ||
2483 | if (next_color != wq->flush_color) { | |
2484 | /* | |
2485 | * Color space is not full. The current work_color | |
2486 | * becomes our flush_color and work_color is advanced | |
2487 | * by one. | |
2488 | */ | |
2489 | BUG_ON(!list_empty(&wq->flusher_overflow)); | |
2490 | this_flusher.flush_color = wq->work_color; | |
2491 | wq->work_color = next_color; | |
2492 | ||
2493 | if (!wq->first_flusher) { | |
2494 | /* no flush in progress, become the first flusher */ | |
2495 | BUG_ON(wq->flush_color != this_flusher.flush_color); | |
2496 | ||
2497 | wq->first_flusher = &this_flusher; | |
2498 | ||
2499 | if (!flush_workqueue_prep_cwqs(wq, wq->flush_color, | |
2500 | wq->work_color)) { | |
2501 | /* nothing to flush, done */ | |
2502 | wq->flush_color = next_color; | |
2503 | wq->first_flusher = NULL; | |
2504 | goto out_unlock; | |
2505 | } | |
2506 | } else { | |
2507 | /* wait in queue */ | |
2508 | BUG_ON(wq->flush_color == this_flusher.flush_color); | |
2509 | list_add_tail(&this_flusher.list, &wq->flusher_queue); | |
2510 | flush_workqueue_prep_cwqs(wq, -1, wq->work_color); | |
2511 | } | |
2512 | } else { | |
2513 | /* | |
2514 | * Oops, color space is full, wait on overflow queue. | |
2515 | * The next flush completion will assign us | |
2516 | * flush_color and transfer to flusher_queue. | |
2517 | */ | |
2518 | list_add_tail(&this_flusher.list, &wq->flusher_overflow); | |
2519 | } | |
2520 | ||
2521 | mutex_unlock(&wq->flush_mutex); | |
2522 | ||
2523 | wait_for_completion(&this_flusher.done); | |
2524 | ||
2525 | /* | |
2526 | * Wake-up-and-cascade phase | |
2527 | * | |
2528 | * First flushers are responsible for cascading flushes and | |
2529 | * handling overflow. Non-first flushers can simply return. | |
2530 | */ | |
2531 | if (wq->first_flusher != &this_flusher) | |
2532 | return; | |
2533 | ||
2534 | mutex_lock(&wq->flush_mutex); | |
2535 | ||
2536 | /* we might have raced, check again with mutex held */ | |
2537 | if (wq->first_flusher != &this_flusher) | |
2538 | goto out_unlock; | |
2539 | ||
2540 | wq->first_flusher = NULL; | |
2541 | ||
2542 | BUG_ON(!list_empty(&this_flusher.list)); | |
2543 | BUG_ON(wq->flush_color != this_flusher.flush_color); | |
2544 | ||
2545 | while (true) { | |
2546 | struct wq_flusher *next, *tmp; | |
2547 | ||
2548 | /* complete all the flushers sharing the current flush color */ | |
2549 | list_for_each_entry_safe(next, tmp, &wq->flusher_queue, list) { | |
2550 | if (next->flush_color != wq->flush_color) | |
2551 | break; | |
2552 | list_del_init(&next->list); | |
2553 | complete(&next->done); | |
2554 | } | |
2555 | ||
2556 | BUG_ON(!list_empty(&wq->flusher_overflow) && | |
2557 | wq->flush_color != work_next_color(wq->work_color)); | |
2558 | ||
2559 | /* this flush_color is finished, advance by one */ | |
2560 | wq->flush_color = work_next_color(wq->flush_color); | |
2561 | ||
2562 | /* one color has been freed, handle overflow queue */ | |
2563 | if (!list_empty(&wq->flusher_overflow)) { | |
2564 | /* | |
2565 | * Assign the same color to all overflowed | |
2566 | * flushers, advance work_color and append to | |
2567 | * flusher_queue. This is the start-to-wait | |
2568 | * phase for these overflowed flushers. | |
2569 | */ | |
2570 | list_for_each_entry(tmp, &wq->flusher_overflow, list) | |
2571 | tmp->flush_color = wq->work_color; | |
2572 | ||
2573 | wq->work_color = work_next_color(wq->work_color); | |
2574 | ||
2575 | list_splice_tail_init(&wq->flusher_overflow, | |
2576 | &wq->flusher_queue); | |
2577 | flush_workqueue_prep_cwqs(wq, -1, wq->work_color); | |
2578 | } | |
2579 | ||
2580 | if (list_empty(&wq->flusher_queue)) { | |
2581 | BUG_ON(wq->flush_color != wq->work_color); | |
2582 | break; | |
2583 | } | |
2584 | ||
2585 | /* | |
2586 | * Need to flush more colors. Make the next flusher | |
2587 | * the new first flusher and arm cwqs. | |
2588 | */ | |
2589 | BUG_ON(wq->flush_color == wq->work_color); | |
2590 | BUG_ON(wq->flush_color != next->flush_color); | |
2591 | ||
2592 | list_del_init(&next->list); | |
2593 | wq->first_flusher = next; | |
2594 | ||
2595 | if (flush_workqueue_prep_cwqs(wq, wq->flush_color, -1)) | |
2596 | break; | |
2597 | ||
2598 | /* | |
2599 | * Meh... this color is already done, clear first | |
2600 | * flusher and repeat cascading. | |
2601 | */ | |
2602 | wq->first_flusher = NULL; | |
2603 | } | |
2604 | ||
2605 | out_unlock: | |
2606 | mutex_unlock(&wq->flush_mutex); | |
2607 | } | |
2608 | EXPORT_SYMBOL_GPL(flush_workqueue); | |
2609 | ||
2610 | /** | |
2611 | * drain_workqueue - drain a workqueue | |
2612 | * @wq: workqueue to drain | |
2613 | * | |
2614 | * Wait until the workqueue becomes empty. While draining is in progress, | |
2615 | * only chain queueing is allowed. IOW, only currently pending or running | |
2616 | * work items on @wq can queue further work items on it. @wq is flushed | |
2617 | * repeatedly until it becomes empty. The number of flushing is detemined | |
2618 | * by the depth of chaining and should be relatively short. Whine if it | |
2619 | * takes too long. | |
2620 | */ | |
2621 | void drain_workqueue(struct workqueue_struct *wq) | |
2622 | { | |
2623 | unsigned int flush_cnt = 0; | |
2624 | unsigned int cpu; | |
2625 | ||
2626 | /* | |
2627 | * __queue_work() needs to test whether there are drainers, is much | |
2628 | * hotter than drain_workqueue() and already looks at @wq->flags. | |
2629 | * Use WQ_DRAINING so that queue doesn't have to check nr_drainers. | |
2630 | */ | |
2631 | spin_lock(&workqueue_lock); | |
2632 | if (!wq->nr_drainers++) | |
2633 | wq->flags |= WQ_DRAINING; | |
2634 | spin_unlock(&workqueue_lock); | |
2635 | reflush: | |
2636 | flush_workqueue(wq); | |
2637 | ||
2638 | for_each_cwq_cpu(cpu, wq) { | |
2639 | struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); | |
2640 | bool drained; | |
2641 | ||
2642 | spin_lock_irq(&cwq->pool->gcwq->lock); | |
2643 | drained = !cwq->nr_active && list_empty(&cwq->delayed_works); | |
2644 | spin_unlock_irq(&cwq->pool->gcwq->lock); | |
2645 | ||
2646 | if (drained) | |
2647 | continue; | |
2648 | ||
2649 | if (++flush_cnt == 10 || | |
2650 | (flush_cnt % 100 == 0 && flush_cnt <= 1000)) | |
2651 | pr_warning("workqueue %s: flush on destruction isn't complete after %u tries\n", | |
2652 | wq->name, flush_cnt); | |
2653 | goto reflush; | |
2654 | } | |
2655 | ||
2656 | spin_lock(&workqueue_lock); | |
2657 | if (!--wq->nr_drainers) | |
2658 | wq->flags &= ~WQ_DRAINING; | |
2659 | spin_unlock(&workqueue_lock); | |
2660 | } | |
2661 | EXPORT_SYMBOL_GPL(drain_workqueue); | |
2662 | ||
2663 | static bool start_flush_work(struct work_struct *work, struct wq_barrier *barr, | |
2664 | bool wait_executing) | |
2665 | { | |
2666 | struct worker *worker = NULL; | |
2667 | struct global_cwq *gcwq; | |
2668 | struct cpu_workqueue_struct *cwq; | |
2669 | ||
2670 | might_sleep(); | |
2671 | gcwq = get_work_gcwq(work); | |
2672 | if (!gcwq) | |
2673 | return false; | |
2674 | ||
2675 | spin_lock_irq(&gcwq->lock); | |
2676 | if (!list_empty(&work->entry)) { | |
2677 | /* | |
2678 | * See the comment near try_to_grab_pending()->smp_rmb(). | |
2679 | * If it was re-queued to a different gcwq under us, we | |
2680 | * are not going to wait. | |
2681 | */ | |
2682 | smp_rmb(); | |
2683 | cwq = get_work_cwq(work); | |
2684 | if (unlikely(!cwq || gcwq != cwq->pool->gcwq)) | |
2685 | goto already_gone; | |
2686 | } else if (wait_executing) { | |
2687 | worker = find_worker_executing_work(gcwq, work); | |
2688 | if (!worker) | |
2689 | goto already_gone; | |
2690 | cwq = worker->current_cwq; | |
2691 | } else | |
2692 | goto already_gone; | |
2693 | ||
2694 | insert_wq_barrier(cwq, barr, work, worker); | |
2695 | spin_unlock_irq(&gcwq->lock); | |
2696 | ||
2697 | /* | |
2698 | * If @max_active is 1 or rescuer is in use, flushing another work | |
2699 | * item on the same workqueue may lead to deadlock. Make sure the | |
2700 | * flusher is not running on the same workqueue by verifying write | |
2701 | * access. | |
2702 | */ | |
2703 | if (cwq->wq->saved_max_active == 1 || cwq->wq->flags & WQ_RESCUER) | |
2704 | lock_map_acquire(&cwq->wq->lockdep_map); | |
2705 | else | |
2706 | lock_map_acquire_read(&cwq->wq->lockdep_map); | |
2707 | lock_map_release(&cwq->wq->lockdep_map); | |
2708 | ||
2709 | return true; | |
2710 | already_gone: | |
2711 | spin_unlock_irq(&gcwq->lock); | |
2712 | return false; | |
2713 | } | |
2714 | ||
2715 | /** | |
2716 | * flush_work - wait for a work to finish executing the last queueing instance | |
2717 | * @work: the work to flush | |
2718 | * | |
2719 | * Wait until @work has finished execution. This function considers | |
2720 | * only the last queueing instance of @work. If @work has been | |
2721 | * enqueued across different CPUs on a non-reentrant workqueue or on | |
2722 | * multiple workqueues, @work might still be executing on return on | |
2723 | * some of the CPUs from earlier queueing. | |
2724 | * | |
2725 | * If @work was queued only on a non-reentrant, ordered or unbound | |
2726 | * workqueue, @work is guaranteed to be idle on return if it hasn't | |
2727 | * been requeued since flush started. | |
2728 | * | |
2729 | * RETURNS: | |
2730 | * %true if flush_work() waited for the work to finish execution, | |
2731 | * %false if it was already idle. | |
2732 | */ | |
2733 | bool flush_work(struct work_struct *work) | |
2734 | { | |
2735 | struct wq_barrier barr; | |
2736 | ||
2737 | lock_map_acquire(&work->lockdep_map); | |
2738 | lock_map_release(&work->lockdep_map); | |
2739 | ||
2740 | if (start_flush_work(work, &barr, true)) { | |
2741 | wait_for_completion(&barr.done); | |
2742 | destroy_work_on_stack(&barr.work); | |
2743 | return true; | |
2744 | } else | |
2745 | return false; | |
2746 | } | |
2747 | EXPORT_SYMBOL_GPL(flush_work); | |
2748 | ||
2749 | static bool wait_on_cpu_work(struct global_cwq *gcwq, struct work_struct *work) | |
2750 | { | |
2751 | struct wq_barrier barr; | |
2752 | struct worker *worker; | |
2753 | ||
2754 | spin_lock_irq(&gcwq->lock); | |
2755 | ||
2756 | worker = find_worker_executing_work(gcwq, work); | |
2757 | if (unlikely(worker)) | |
2758 | insert_wq_barrier(worker->current_cwq, &barr, work, worker); | |
2759 | ||
2760 | spin_unlock_irq(&gcwq->lock); | |
2761 | ||
2762 | if (unlikely(worker)) { | |
2763 | wait_for_completion(&barr.done); | |
2764 | destroy_work_on_stack(&barr.work); | |
2765 | return true; | |
2766 | } else | |
2767 | return false; | |
2768 | } | |
2769 | ||
2770 | static bool wait_on_work(struct work_struct *work) | |
2771 | { | |
2772 | bool ret = false; | |
2773 | int cpu; | |
2774 | ||
2775 | might_sleep(); | |
2776 | ||
2777 | lock_map_acquire(&work->lockdep_map); | |
2778 | lock_map_release(&work->lockdep_map); | |
2779 | ||
2780 | for_each_gcwq_cpu(cpu) | |
2781 | ret |= wait_on_cpu_work(get_gcwq(cpu), work); | |
2782 | return ret; | |
2783 | } | |
2784 | ||
2785 | /** | |
2786 | * flush_work_sync - wait until a work has finished execution | |
2787 | * @work: the work to flush | |
2788 | * | |
2789 | * Wait until @work has finished execution. On return, it's | |
2790 | * guaranteed that all queueing instances of @work which happened | |
2791 | * before this function is called are finished. In other words, if | |
2792 | * @work hasn't been requeued since this function was called, @work is | |
2793 | * guaranteed to be idle on return. | |
2794 | * | |
2795 | * RETURNS: | |
2796 | * %true if flush_work_sync() waited for the work to finish execution, | |
2797 | * %false if it was already idle. | |
2798 | */ | |
2799 | bool flush_work_sync(struct work_struct *work) | |
2800 | { | |
2801 | struct wq_barrier barr; | |
2802 | bool pending, waited; | |
2803 | ||
2804 | /* we'll wait for executions separately, queue barr only if pending */ | |
2805 | pending = start_flush_work(work, &barr, false); | |
2806 | ||
2807 | /* wait for executions to finish */ | |
2808 | waited = wait_on_work(work); | |
2809 | ||
2810 | /* wait for the pending one */ | |
2811 | if (pending) { | |
2812 | wait_for_completion(&barr.done); | |
2813 | destroy_work_on_stack(&barr.work); | |
2814 | } | |
2815 | ||
2816 | return pending || waited; | |
2817 | } | |
2818 | EXPORT_SYMBOL_GPL(flush_work_sync); | |
2819 | ||
2820 | static bool __cancel_work_timer(struct work_struct *work, | |
2821 | struct timer_list* timer) | |
2822 | { | |
2823 | int ret; | |
2824 | ||
2825 | do { | |
2826 | ret = (timer && likely(del_timer(timer))); | |
2827 | if (!ret) | |
2828 | ret = try_to_grab_pending(work); | |
2829 | wait_on_work(work); | |
2830 | } while (unlikely(ret < 0)); | |
2831 | ||
2832 | clear_work_data(work); | |
2833 | return ret; | |
2834 | } | |
2835 | ||
2836 | /** | |
2837 | * cancel_work_sync - cancel a work and wait for it to finish | |
2838 | * @work: the work to cancel | |
2839 | * | |
2840 | * Cancel @work and wait for its execution to finish. This function | |
2841 | * can be used even if the work re-queues itself or migrates to | |
2842 | * another workqueue. On return from this function, @work is | |
2843 | * guaranteed to be not pending or executing on any CPU. | |
2844 | * | |
2845 | * cancel_work_sync(&delayed_work->work) must not be used for | |
2846 | * delayed_work's. Use cancel_delayed_work_sync() instead. | |
2847 | * | |
2848 | * The caller must ensure that the workqueue on which @work was last | |
2849 | * queued can't be destroyed before this function returns. | |
2850 | * | |
2851 | * RETURNS: | |
2852 | * %true if @work was pending, %false otherwise. | |
2853 | */ | |
2854 | bool cancel_work_sync(struct work_struct *work) | |
2855 | { | |
2856 | return __cancel_work_timer(work, NULL); | |
2857 | } | |
2858 | EXPORT_SYMBOL_GPL(cancel_work_sync); | |
2859 | ||
2860 | /** | |
2861 | * flush_delayed_work - wait for a dwork to finish executing the last queueing | |
2862 | * @dwork: the delayed work to flush | |
2863 | * | |
2864 | * Delayed timer is cancelled and the pending work is queued for | |
2865 | * immediate execution. Like flush_work(), this function only | |
2866 | * considers the last queueing instance of @dwork. | |
2867 | * | |
2868 | * RETURNS: | |
2869 | * %true if flush_work() waited for the work to finish execution, | |
2870 | * %false if it was already idle. | |
2871 | */ | |
2872 | bool flush_delayed_work(struct delayed_work *dwork) | |
2873 | { | |
2874 | local_irq_disable(); | |
2875 | if (del_timer_sync(&dwork->timer)) | |
2876 | __queue_work(WORK_CPU_UNBOUND, | |
2877 | get_work_cwq(&dwork->work)->wq, &dwork->work); | |
2878 | local_irq_enable(); | |
2879 | return flush_work(&dwork->work); | |
2880 | } | |
2881 | EXPORT_SYMBOL(flush_delayed_work); | |
2882 | ||
2883 | /** | |
2884 | * flush_delayed_work_sync - wait for a dwork to finish | |
2885 | * @dwork: the delayed work to flush | |
2886 | * | |
2887 | * Delayed timer is cancelled and the pending work is queued for | |
2888 | * execution immediately. Other than timer handling, its behavior | |
2889 | * is identical to flush_work_sync(). | |
2890 | * | |
2891 | * RETURNS: | |
2892 | * %true if flush_work_sync() waited for the work to finish execution, | |
2893 | * %false if it was already idle. | |
2894 | */ | |
2895 | bool flush_delayed_work_sync(struct delayed_work *dwork) | |
2896 | { | |
2897 | local_irq_disable(); | |
2898 | if (del_timer_sync(&dwork->timer)) | |
2899 | __queue_work(WORK_CPU_UNBOUND, | |
2900 | get_work_cwq(&dwork->work)->wq, &dwork->work); | |
2901 | local_irq_enable(); | |
2902 | return flush_work_sync(&dwork->work); | |
2903 | } | |
2904 | EXPORT_SYMBOL(flush_delayed_work_sync); | |
2905 | ||
2906 | /** | |
2907 | * cancel_delayed_work_sync - cancel a delayed work and wait for it to finish | |
2908 | * @dwork: the delayed work cancel | |
2909 | * | |
2910 | * This is cancel_work_sync() for delayed works. | |
2911 | * | |
2912 | * RETURNS: | |
2913 | * %true if @dwork was pending, %false otherwise. | |
2914 | */ | |
2915 | bool cancel_delayed_work_sync(struct delayed_work *dwork) | |
2916 | { | |
2917 | return __cancel_work_timer(&dwork->work, &dwork->timer); | |
2918 | } | |
2919 | EXPORT_SYMBOL(cancel_delayed_work_sync); | |
2920 | ||
2921 | /** | |
2922 | * schedule_work_on - put work task on a specific cpu | |
2923 | * @cpu: cpu to put the work task on | |
2924 | * @work: job to be done | |
2925 | * | |
2926 | * This puts a job on a specific cpu | |
2927 | */ | |
2928 | bool schedule_work_on(int cpu, struct work_struct *work) | |
2929 | { | |
2930 | return queue_work_on(cpu, system_wq, work); | |
2931 | } | |
2932 | EXPORT_SYMBOL(schedule_work_on); | |
2933 | ||
2934 | /** | |
2935 | * schedule_work - put work task in global workqueue | |
2936 | * @work: job to be done | |
2937 | * | |
2938 | * Returns %false if @work was already on the kernel-global workqueue and | |
2939 | * %true otherwise. | |
2940 | * | |
2941 | * This puts a job in the kernel-global workqueue if it was not already | |
2942 | * queued and leaves it in the same position on the kernel-global | |
2943 | * workqueue otherwise. | |
2944 | */ | |
2945 | bool schedule_work(struct work_struct *work) | |
2946 | { | |
2947 | return queue_work(system_wq, work); | |
2948 | } | |
2949 | EXPORT_SYMBOL(schedule_work); | |
2950 | ||
2951 | /** | |
2952 | * schedule_delayed_work_on - queue work in global workqueue on CPU after delay | |
2953 | * @cpu: cpu to use | |
2954 | * @dwork: job to be done | |
2955 | * @delay: number of jiffies to wait | |
2956 | * | |
2957 | * After waiting for a given time this puts a job in the kernel-global | |
2958 | * workqueue on the specified CPU. | |
2959 | */ | |
2960 | bool schedule_delayed_work_on(int cpu, struct delayed_work *dwork, | |
2961 | unsigned long delay) | |
2962 | { | |
2963 | return queue_delayed_work_on(cpu, system_wq, dwork, delay); | |
2964 | } | |
2965 | EXPORT_SYMBOL(schedule_delayed_work_on); | |
2966 | ||
2967 | /** | |
2968 | * schedule_delayed_work - put work task in global workqueue after delay | |
2969 | * @dwork: job to be done | |
2970 | * @delay: number of jiffies to wait or 0 for immediate execution | |
2971 | * | |
2972 | * After waiting for a given time this puts a job in the kernel-global | |
2973 | * workqueue. | |
2974 | */ | |
2975 | bool schedule_delayed_work(struct delayed_work *dwork, unsigned long delay) | |
2976 | { | |
2977 | return queue_delayed_work(system_wq, dwork, delay); | |
2978 | } | |
2979 | EXPORT_SYMBOL(schedule_delayed_work); | |
2980 | ||
2981 | /** | |
2982 | * schedule_on_each_cpu - execute a function synchronously on each online CPU | |
2983 | * @func: the function to call | |
2984 | * | |
2985 | * schedule_on_each_cpu() executes @func on each online CPU using the | |
2986 | * system workqueue and blocks until all CPUs have completed. | |
2987 | * schedule_on_each_cpu() is very slow. | |
2988 | * | |
2989 | * RETURNS: | |
2990 | * 0 on success, -errno on failure. | |
2991 | */ | |
2992 | int schedule_on_each_cpu(work_func_t func) | |
2993 | { | |
2994 | int cpu; | |
2995 | struct work_struct __percpu *works; | |
2996 | ||
2997 | works = alloc_percpu(struct work_struct); | |
2998 | if (!works) | |
2999 | return -ENOMEM; | |
3000 | ||
3001 | get_online_cpus(); | |
3002 | ||
3003 | for_each_online_cpu(cpu) { | |
3004 | struct work_struct *work = per_cpu_ptr(works, cpu); | |
3005 | ||
3006 | INIT_WORK(work, func); | |
3007 | schedule_work_on(cpu, work); | |
3008 | } | |
3009 | ||
3010 | for_each_online_cpu(cpu) | |
3011 | flush_work(per_cpu_ptr(works, cpu)); | |
3012 | ||
3013 | put_online_cpus(); | |
3014 | free_percpu(works); | |
3015 | return 0; | |
3016 | } | |
3017 | ||
3018 | /** | |
3019 | * flush_scheduled_work - ensure that any scheduled work has run to completion. | |
3020 | * | |
3021 | * Forces execution of the kernel-global workqueue and blocks until its | |
3022 | * completion. | |
3023 | * | |
3024 | * Think twice before calling this function! It's very easy to get into | |
3025 | * trouble if you don't take great care. Either of the following situations | |
3026 | * will lead to deadlock: | |
3027 | * | |
3028 | * One of the work items currently on the workqueue needs to acquire | |
3029 | * a lock held by your code or its caller. | |
3030 | * | |
3031 | * Your code is running in the context of a work routine. | |
3032 | * | |
3033 | * They will be detected by lockdep when they occur, but the first might not | |
3034 | * occur very often. It depends on what work items are on the workqueue and | |
3035 | * what locks they need, which you have no control over. | |
3036 | * | |
3037 | * In most situations flushing the entire workqueue is overkill; you merely | |
3038 | * need to know that a particular work item isn't queued and isn't running. | |
3039 | * In such cases you should use cancel_delayed_work_sync() or | |
3040 | * cancel_work_sync() instead. | |
3041 | */ | |
3042 | void flush_scheduled_work(void) | |
3043 | { | |
3044 | flush_workqueue(system_wq); | |
3045 | } | |
3046 | EXPORT_SYMBOL(flush_scheduled_work); | |
3047 | ||
3048 | /** | |
3049 | * execute_in_process_context - reliably execute the routine with user context | |
3050 | * @fn: the function to execute | |
3051 | * @ew: guaranteed storage for the execute work structure (must | |
3052 | * be available when the work executes) | |
3053 | * | |
3054 | * Executes the function immediately if process context is available, | |
3055 | * otherwise schedules the function for delayed execution. | |
3056 | * | |
3057 | * Returns: 0 - function was executed | |
3058 | * 1 - function was scheduled for execution | |
3059 | */ | |
3060 | int execute_in_process_context(work_func_t fn, struct execute_work *ew) | |
3061 | { | |
3062 | if (!in_interrupt()) { | |
3063 | fn(&ew->work); | |
3064 | return 0; | |
3065 | } | |
3066 | ||
3067 | INIT_WORK(&ew->work, fn); | |
3068 | schedule_work(&ew->work); | |
3069 | ||
3070 | return 1; | |
3071 | } | |
3072 | EXPORT_SYMBOL_GPL(execute_in_process_context); | |
3073 | ||
3074 | int keventd_up(void) | |
3075 | { | |
3076 | return system_wq != NULL; | |
3077 | } | |
3078 | ||
3079 | static int alloc_cwqs(struct workqueue_struct *wq) | |
3080 | { | |
3081 | /* | |
3082 | * cwqs are forced aligned according to WORK_STRUCT_FLAG_BITS. | |
3083 | * Make sure that the alignment isn't lower than that of | |
3084 | * unsigned long long. | |
3085 | */ | |
3086 | const size_t size = sizeof(struct cpu_workqueue_struct); | |
3087 | const size_t align = max_t(size_t, 1 << WORK_STRUCT_FLAG_BITS, | |
3088 | __alignof__(unsigned long long)); | |
3089 | ||
3090 | if (!(wq->flags & WQ_UNBOUND)) | |
3091 | wq->cpu_wq.pcpu = __alloc_percpu(size, align); | |
3092 | else { | |
3093 | void *ptr; | |
3094 | ||
3095 | /* | |
3096 | * Allocate enough room to align cwq and put an extra | |
3097 | * pointer at the end pointing back to the originally | |
3098 | * allocated pointer which will be used for free. | |
3099 | */ | |
3100 | ptr = kzalloc(size + align + sizeof(void *), GFP_KERNEL); | |
3101 | if (ptr) { | |
3102 | wq->cpu_wq.single = PTR_ALIGN(ptr, align); | |
3103 | *(void **)(wq->cpu_wq.single + 1) = ptr; | |
3104 | } | |
3105 | } | |
3106 | ||
3107 | /* just in case, make sure it's actually aligned */ | |
3108 | BUG_ON(!IS_ALIGNED(wq->cpu_wq.v, align)); | |
3109 | return wq->cpu_wq.v ? 0 : -ENOMEM; | |
3110 | } | |
3111 | ||
3112 | static void free_cwqs(struct workqueue_struct *wq) | |
3113 | { | |
3114 | if (!(wq->flags & WQ_UNBOUND)) | |
3115 | free_percpu(wq->cpu_wq.pcpu); | |
3116 | else if (wq->cpu_wq.single) { | |
3117 | /* the pointer to free is stored right after the cwq */ | |
3118 | kfree(*(void **)(wq->cpu_wq.single + 1)); | |
3119 | } | |
3120 | } | |
3121 | ||
3122 | static int wq_clamp_max_active(int max_active, unsigned int flags, | |
3123 | const char *name) | |
3124 | { | |
3125 | int lim = flags & WQ_UNBOUND ? WQ_UNBOUND_MAX_ACTIVE : WQ_MAX_ACTIVE; | |
3126 | ||
3127 | if (max_active < 1 || max_active > lim) | |
3128 | printk(KERN_WARNING "workqueue: max_active %d requested for %s " | |
3129 | "is out of range, clamping between %d and %d\n", | |
3130 | max_active, name, 1, lim); | |
3131 | ||
3132 | return clamp_val(max_active, 1, lim); | |
3133 | } | |
3134 | ||
3135 | struct workqueue_struct *__alloc_workqueue_key(const char *fmt, | |
3136 | unsigned int flags, | |
3137 | int max_active, | |
3138 | struct lock_class_key *key, | |
3139 | const char *lock_name, ...) | |
3140 | { | |
3141 | va_list args, args1; | |
3142 | struct workqueue_struct *wq; | |
3143 | unsigned int cpu; | |
3144 | size_t namelen; | |
3145 | ||
3146 | /* determine namelen, allocate wq and format name */ | |
3147 | va_start(args, lock_name); | |
3148 | va_copy(args1, args); | |
3149 | namelen = vsnprintf(NULL, 0, fmt, args) + 1; | |
3150 | ||
3151 | wq = kzalloc(sizeof(*wq) + namelen, GFP_KERNEL); | |
3152 | if (!wq) | |
3153 | goto err; | |
3154 | ||
3155 | vsnprintf(wq->name, namelen, fmt, args1); | |
3156 | va_end(args); | |
3157 | va_end(args1); | |
3158 | ||
3159 | /* | |
3160 | * Workqueues which may be used during memory reclaim should | |
3161 | * have a rescuer to guarantee forward progress. | |
3162 | */ | |
3163 | if (flags & WQ_MEM_RECLAIM) | |
3164 | flags |= WQ_RESCUER; | |
3165 | ||
3166 | max_active = max_active ?: WQ_DFL_ACTIVE; | |
3167 | max_active = wq_clamp_max_active(max_active, flags, wq->name); | |
3168 | ||
3169 | /* init wq */ | |
3170 | wq->flags = flags; | |
3171 | wq->saved_max_active = max_active; | |
3172 | mutex_init(&wq->flush_mutex); | |
3173 | atomic_set(&wq->nr_cwqs_to_flush, 0); | |
3174 | INIT_LIST_HEAD(&wq->flusher_queue); | |
3175 | INIT_LIST_HEAD(&wq->flusher_overflow); | |
3176 | ||
3177 | lockdep_init_map(&wq->lockdep_map, lock_name, key, 0); | |
3178 | INIT_LIST_HEAD(&wq->list); | |
3179 | ||
3180 | if (alloc_cwqs(wq) < 0) | |
3181 | goto err; | |
3182 | ||
3183 | for_each_cwq_cpu(cpu, wq) { | |
3184 | struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); | |
3185 | struct global_cwq *gcwq = get_gcwq(cpu); | |
3186 | int pool_idx = (bool)(flags & WQ_HIGHPRI); | |
3187 | ||
3188 | BUG_ON((unsigned long)cwq & WORK_STRUCT_FLAG_MASK); | |
3189 | cwq->pool = &gcwq->pools[pool_idx]; | |
3190 | cwq->wq = wq; | |
3191 | cwq->flush_color = -1; | |
3192 | cwq->max_active = max_active; | |
3193 | INIT_LIST_HEAD(&cwq->delayed_works); | |
3194 | } | |
3195 | ||
3196 | if (flags & WQ_RESCUER) { | |
3197 | struct worker *rescuer; | |
3198 | ||
3199 | if (!alloc_mayday_mask(&wq->mayday_mask, GFP_KERNEL)) | |
3200 | goto err; | |
3201 | ||
3202 | wq->rescuer = rescuer = alloc_worker(); | |
3203 | if (!rescuer) | |
3204 | goto err; | |
3205 | ||
3206 | rescuer->task = kthread_create(rescuer_thread, wq, "%s", | |
3207 | wq->name); | |
3208 | if (IS_ERR(rescuer->task)) | |
3209 | goto err; | |
3210 | ||
3211 | rescuer->task->flags |= PF_THREAD_BOUND; | |
3212 | wake_up_process(rescuer->task); | |
3213 | } | |
3214 | ||
3215 | /* | |
3216 | * workqueue_lock protects global freeze state and workqueues | |
3217 | * list. Grab it, set max_active accordingly and add the new | |
3218 | * workqueue to workqueues list. | |
3219 | */ | |
3220 | spin_lock(&workqueue_lock); | |
3221 | ||
3222 | if (workqueue_freezing && wq->flags & WQ_FREEZABLE) | |
3223 | for_each_cwq_cpu(cpu, wq) | |
3224 | get_cwq(cpu, wq)->max_active = 0; | |
3225 | ||
3226 | list_add(&wq->list, &workqueues); | |
3227 | ||
3228 | spin_unlock(&workqueue_lock); | |
3229 | ||
3230 | return wq; | |
3231 | err: | |
3232 | if (wq) { | |
3233 | free_cwqs(wq); | |
3234 | free_mayday_mask(wq->mayday_mask); | |
3235 | kfree(wq->rescuer); | |
3236 | kfree(wq); | |
3237 | } | |
3238 | return NULL; | |
3239 | } | |
3240 | EXPORT_SYMBOL_GPL(__alloc_workqueue_key); | |
3241 | ||
3242 | /** | |
3243 | * destroy_workqueue - safely terminate a workqueue | |
3244 | * @wq: target workqueue | |
3245 | * | |
3246 | * Safely destroy a workqueue. All work currently pending will be done first. | |
3247 | */ | |
3248 | void destroy_workqueue(struct workqueue_struct *wq) | |
3249 | { | |
3250 | unsigned int cpu; | |
3251 | ||
3252 | /* drain it before proceeding with destruction */ | |
3253 | drain_workqueue(wq); | |
3254 | ||
3255 | /* | |
3256 | * wq list is used to freeze wq, remove from list after | |
3257 | * flushing is complete in case freeze races us. | |
3258 | */ | |
3259 | spin_lock(&workqueue_lock); | |
3260 | list_del(&wq->list); | |
3261 | spin_unlock(&workqueue_lock); | |
3262 | ||
3263 | /* sanity check */ | |
3264 | for_each_cwq_cpu(cpu, wq) { | |
3265 | struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); | |
3266 | int i; | |
3267 | ||
3268 | for (i = 0; i < WORK_NR_COLORS; i++) | |
3269 | BUG_ON(cwq->nr_in_flight[i]); | |
3270 | BUG_ON(cwq->nr_active); | |
3271 | BUG_ON(!list_empty(&cwq->delayed_works)); | |
3272 | } | |
3273 | ||
3274 | if (wq->flags & WQ_RESCUER) { | |
3275 | kthread_stop(wq->rescuer->task); | |
3276 | free_mayday_mask(wq->mayday_mask); | |
3277 | kfree(wq->rescuer); | |
3278 | } | |
3279 | ||
3280 | free_cwqs(wq); | |
3281 | kfree(wq); | |
3282 | } | |
3283 | EXPORT_SYMBOL_GPL(destroy_workqueue); | |
3284 | ||
3285 | /** | |
3286 | * workqueue_set_max_active - adjust max_active of a workqueue | |
3287 | * @wq: target workqueue | |
3288 | * @max_active: new max_active value. | |
3289 | * | |
3290 | * Set max_active of @wq to @max_active. | |
3291 | * | |
3292 | * CONTEXT: | |
3293 | * Don't call from IRQ context. | |
3294 | */ | |
3295 | void workqueue_set_max_active(struct workqueue_struct *wq, int max_active) | |
3296 | { | |
3297 | unsigned int cpu; | |
3298 | ||
3299 | max_active = wq_clamp_max_active(max_active, wq->flags, wq->name); | |
3300 | ||
3301 | spin_lock(&workqueue_lock); | |
3302 | ||
3303 | wq->saved_max_active = max_active; | |
3304 | ||
3305 | for_each_cwq_cpu(cpu, wq) { | |
3306 | struct global_cwq *gcwq = get_gcwq(cpu); | |
3307 | ||
3308 | spin_lock_irq(&gcwq->lock); | |
3309 | ||
3310 | if (!(wq->flags & WQ_FREEZABLE) || | |
3311 | !(gcwq->flags & GCWQ_FREEZING)) | |
3312 | get_cwq(gcwq->cpu, wq)->max_active = max_active; | |
3313 | ||
3314 | spin_unlock_irq(&gcwq->lock); | |
3315 | } | |
3316 | ||
3317 | spin_unlock(&workqueue_lock); | |
3318 | } | |
3319 | EXPORT_SYMBOL_GPL(workqueue_set_max_active); | |
3320 | ||
3321 | /** | |
3322 | * workqueue_congested - test whether a workqueue is congested | |
3323 | * @cpu: CPU in question | |
3324 | * @wq: target workqueue | |
3325 | * | |
3326 | * Test whether @wq's cpu workqueue for @cpu is congested. There is | |
3327 | * no synchronization around this function and the test result is | |
3328 | * unreliable and only useful as advisory hints or for debugging. | |
3329 | * | |
3330 | * RETURNS: | |
3331 | * %true if congested, %false otherwise. | |
3332 | */ | |
3333 | bool workqueue_congested(unsigned int cpu, struct workqueue_struct *wq) | |
3334 | { | |
3335 | struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); | |
3336 | ||
3337 | return !list_empty(&cwq->delayed_works); | |
3338 | } | |
3339 | EXPORT_SYMBOL_GPL(workqueue_congested); | |
3340 | ||
3341 | /** | |
3342 | * work_cpu - return the last known associated cpu for @work | |
3343 | * @work: the work of interest | |
3344 | * | |
3345 | * RETURNS: | |
3346 | * CPU number if @work was ever queued. WORK_CPU_NONE otherwise. | |
3347 | */ | |
3348 | unsigned int work_cpu(struct work_struct *work) | |
3349 | { | |
3350 | struct global_cwq *gcwq = get_work_gcwq(work); | |
3351 | ||
3352 | return gcwq ? gcwq->cpu : WORK_CPU_NONE; | |
3353 | } | |
3354 | EXPORT_SYMBOL_GPL(work_cpu); | |
3355 | ||
3356 | /** | |
3357 | * work_busy - test whether a work is currently pending or running | |
3358 | * @work: the work to be tested | |
3359 | * | |
3360 | * Test whether @work is currently pending or running. There is no | |
3361 | * synchronization around this function and the test result is | |
3362 | * unreliable and only useful as advisory hints or for debugging. | |
3363 | * Especially for reentrant wqs, the pending state might hide the | |
3364 | * running state. | |
3365 | * | |
3366 | * RETURNS: | |
3367 | * OR'd bitmask of WORK_BUSY_* bits. | |
3368 | */ | |
3369 | unsigned int work_busy(struct work_struct *work) | |
3370 | { | |
3371 | struct global_cwq *gcwq = get_work_gcwq(work); | |
3372 | unsigned long flags; | |
3373 | unsigned int ret = 0; | |
3374 | ||
3375 | if (!gcwq) | |
3376 | return false; | |
3377 | ||
3378 | spin_lock_irqsave(&gcwq->lock, flags); | |
3379 | ||
3380 | if (work_pending(work)) | |
3381 | ret |= WORK_BUSY_PENDING; | |
3382 | if (find_worker_executing_work(gcwq, work)) | |
3383 | ret |= WORK_BUSY_RUNNING; | |
3384 | ||
3385 | spin_unlock_irqrestore(&gcwq->lock, flags); | |
3386 | ||
3387 | return ret; | |
3388 | } | |
3389 | EXPORT_SYMBOL_GPL(work_busy); | |
3390 | ||
3391 | /* | |
3392 | * CPU hotplug. | |
3393 | * | |
3394 | * There are two challenges in supporting CPU hotplug. Firstly, there | |
3395 | * are a lot of assumptions on strong associations among work, cwq and | |
3396 | * gcwq which make migrating pending and scheduled works very | |
3397 | * difficult to implement without impacting hot paths. Secondly, | |
3398 | * gcwqs serve mix of short, long and very long running works making | |
3399 | * blocked draining impractical. | |
3400 | * | |
3401 | * This is solved by allowing a gcwq to be disassociated from the CPU | |
3402 | * running as an unbound one and allowing it to be reattached later if the | |
3403 | * cpu comes back online. | |
3404 | */ | |
3405 | ||
3406 | /* claim manager positions of all pools */ | |
3407 | static void gcwq_claim_management_and_lock(struct global_cwq *gcwq) | |
3408 | { | |
3409 | struct worker_pool *pool; | |
3410 | ||
3411 | for_each_worker_pool(pool, gcwq) | |
3412 | mutex_lock_nested(&pool->manager_mutex, pool - gcwq->pools); | |
3413 | spin_lock_irq(&gcwq->lock); | |
3414 | } | |
3415 | ||
3416 | /* release manager positions */ | |
3417 | static void gcwq_release_management_and_unlock(struct global_cwq *gcwq) | |
3418 | { | |
3419 | struct worker_pool *pool; | |
3420 | ||
3421 | spin_unlock_irq(&gcwq->lock); | |
3422 | for_each_worker_pool(pool, gcwq) | |
3423 | mutex_unlock(&pool->manager_mutex); | |
3424 | } | |
3425 | ||
3426 | static void gcwq_unbind_fn(struct work_struct *work) | |
3427 | { | |
3428 | struct global_cwq *gcwq = get_gcwq(smp_processor_id()); | |
3429 | struct worker_pool *pool; | |
3430 | struct worker *worker; | |
3431 | struct hlist_node *pos; | |
3432 | int i; | |
3433 | ||
3434 | BUG_ON(gcwq->cpu != smp_processor_id()); | |
3435 | ||
3436 | gcwq_claim_management_and_lock(gcwq); | |
3437 | ||
3438 | /* | |
3439 | * We've claimed all manager positions. Make all workers unbound | |
3440 | * and set DISASSOCIATED. Before this, all workers except for the | |
3441 | * ones which are still executing works from before the last CPU | |
3442 | * down must be on the cpu. After this, they may become diasporas. | |
3443 | */ | |
3444 | for_each_worker_pool(pool, gcwq) | |
3445 | list_for_each_entry(worker, &pool->idle_list, entry) | |
3446 | worker->flags |= WORKER_UNBOUND; | |
3447 | ||
3448 | for_each_busy_worker(worker, i, pos, gcwq) | |
3449 | worker->flags |= WORKER_UNBOUND; | |
3450 | ||
3451 | gcwq->flags |= GCWQ_DISASSOCIATED; | |
3452 | ||
3453 | gcwq_release_management_and_unlock(gcwq); | |
3454 | ||
3455 | /* | |
3456 | * Call schedule() so that we cross rq->lock and thus can guarantee | |
3457 | * sched callbacks see the %WORKER_UNBOUND flag. This is necessary | |
3458 | * as scheduler callbacks may be invoked from other cpus. | |
3459 | */ | |
3460 | schedule(); | |
3461 | ||
3462 | /* | |
3463 | * Sched callbacks are disabled now. Zap nr_running. After this, | |
3464 | * nr_running stays zero and need_more_worker() and keep_working() | |
3465 | * are always true as long as the worklist is not empty. @gcwq now | |
3466 | * behaves as unbound (in terms of concurrency management) gcwq | |
3467 | * which is served by workers tied to the CPU. | |
3468 | * | |
3469 | * On return from this function, the current worker would trigger | |
3470 | * unbound chain execution of pending work items if other workers | |
3471 | * didn't already. | |
3472 | */ | |
3473 | for_each_worker_pool(pool, gcwq) | |
3474 | atomic_set(get_pool_nr_running(pool), 0); | |
3475 | } | |
3476 | ||
3477 | /* | |
3478 | * Workqueues should be brought up before normal priority CPU notifiers. | |
3479 | * This will be registered high priority CPU notifier. | |
3480 | */ | |
3481 | static int __devinit workqueue_cpu_up_callback(struct notifier_block *nfb, | |
3482 | unsigned long action, | |
3483 | void *hcpu) | |
3484 | { | |
3485 | unsigned int cpu = (unsigned long)hcpu; | |
3486 | struct global_cwq *gcwq = get_gcwq(cpu); | |
3487 | struct worker_pool *pool; | |
3488 | ||
3489 | switch (action & ~CPU_TASKS_FROZEN) { | |
3490 | case CPU_UP_PREPARE: | |
3491 | for_each_worker_pool(pool, gcwq) { | |
3492 | struct worker *worker; | |
3493 | ||
3494 | if (pool->nr_workers) | |
3495 | continue; | |
3496 | ||
3497 | worker = create_worker(pool); | |
3498 | if (!worker) | |
3499 | return NOTIFY_BAD; | |
3500 | ||
3501 | spin_lock_irq(&gcwq->lock); | |
3502 | start_worker(worker); | |
3503 | spin_unlock_irq(&gcwq->lock); | |
3504 | } | |
3505 | break; | |
3506 | ||
3507 | case CPU_DOWN_FAILED: | |
3508 | case CPU_ONLINE: | |
3509 | gcwq_claim_management_and_lock(gcwq); | |
3510 | gcwq->flags &= ~GCWQ_DISASSOCIATED; | |
3511 | rebind_workers(gcwq); | |
3512 | gcwq_release_management_and_unlock(gcwq); | |
3513 | break; | |
3514 | } | |
3515 | return NOTIFY_OK; | |
3516 | } | |
3517 | ||
3518 | /* | |
3519 | * Workqueues should be brought down after normal priority CPU notifiers. | |
3520 | * This will be registered as low priority CPU notifier. | |
3521 | */ | |
3522 | static int __devinit workqueue_cpu_down_callback(struct notifier_block *nfb, | |
3523 | unsigned long action, | |
3524 | void *hcpu) | |
3525 | { | |
3526 | unsigned int cpu = (unsigned long)hcpu; | |
3527 | struct work_struct unbind_work; | |
3528 | ||
3529 | switch (action & ~CPU_TASKS_FROZEN) { | |
3530 | case CPU_DOWN_PREPARE: | |
3531 | /* unbinding should happen on the local CPU */ | |
3532 | INIT_WORK_ONSTACK(&unbind_work, gcwq_unbind_fn); | |
3533 | schedule_work_on(cpu, &unbind_work); | |
3534 | flush_work(&unbind_work); | |
3535 | break; | |
3536 | } | |
3537 | return NOTIFY_OK; | |
3538 | } | |
3539 | ||
3540 | #ifdef CONFIG_SMP | |
3541 | ||
3542 | struct work_for_cpu { | |
3543 | struct completion completion; | |
3544 | long (*fn)(void *); | |
3545 | void *arg; | |
3546 | long ret; | |
3547 | }; | |
3548 | ||
3549 | static int do_work_for_cpu(void *_wfc) | |
3550 | { | |
3551 | struct work_for_cpu *wfc = _wfc; | |
3552 | wfc->ret = wfc->fn(wfc->arg); | |
3553 | complete(&wfc->completion); | |
3554 | return 0; | |
3555 | } | |
3556 | ||
3557 | /** | |
3558 | * work_on_cpu - run a function in user context on a particular cpu | |
3559 | * @cpu: the cpu to run on | |
3560 | * @fn: the function to run | |
3561 | * @arg: the function arg | |
3562 | * | |
3563 | * This will return the value @fn returns. | |
3564 | * It is up to the caller to ensure that the cpu doesn't go offline. | |
3565 | * The caller must not hold any locks which would prevent @fn from completing. | |
3566 | */ | |
3567 | long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg) | |
3568 | { | |
3569 | struct task_struct *sub_thread; | |
3570 | struct work_for_cpu wfc = { | |
3571 | .completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion), | |
3572 | .fn = fn, | |
3573 | .arg = arg, | |
3574 | }; | |
3575 | ||
3576 | sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu"); | |
3577 | if (IS_ERR(sub_thread)) | |
3578 | return PTR_ERR(sub_thread); | |
3579 | kthread_bind(sub_thread, cpu); | |
3580 | wake_up_process(sub_thread); | |
3581 | wait_for_completion(&wfc.completion); | |
3582 | return wfc.ret; | |
3583 | } | |
3584 | EXPORT_SYMBOL_GPL(work_on_cpu); | |
3585 | #endif /* CONFIG_SMP */ | |
3586 | ||
3587 | #ifdef CONFIG_FREEZER | |
3588 | ||
3589 | /** | |
3590 | * freeze_workqueues_begin - begin freezing workqueues | |
3591 | * | |
3592 | * Start freezing workqueues. After this function returns, all freezable | |
3593 | * workqueues will queue new works to their frozen_works list instead of | |
3594 | * gcwq->worklist. | |
3595 | * | |
3596 | * CONTEXT: | |
3597 | * Grabs and releases workqueue_lock and gcwq->lock's. | |
3598 | */ | |
3599 | void freeze_workqueues_begin(void) | |
3600 | { | |
3601 | unsigned int cpu; | |
3602 | ||
3603 | spin_lock(&workqueue_lock); | |
3604 | ||
3605 | BUG_ON(workqueue_freezing); | |
3606 | workqueue_freezing = true; | |
3607 | ||
3608 | for_each_gcwq_cpu(cpu) { | |
3609 | struct global_cwq *gcwq = get_gcwq(cpu); | |
3610 | struct workqueue_struct *wq; | |
3611 | ||
3612 | spin_lock_irq(&gcwq->lock); | |
3613 | ||
3614 | BUG_ON(gcwq->flags & GCWQ_FREEZING); | |
3615 | gcwq->flags |= GCWQ_FREEZING; | |
3616 | ||
3617 | list_for_each_entry(wq, &workqueues, list) { | |
3618 | struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); | |
3619 | ||
3620 | if (cwq && wq->flags & WQ_FREEZABLE) | |
3621 | cwq->max_active = 0; | |
3622 | } | |
3623 | ||
3624 | spin_unlock_irq(&gcwq->lock); | |
3625 | } | |
3626 | ||
3627 | spin_unlock(&workqueue_lock); | |
3628 | } | |
3629 | ||
3630 | /** | |
3631 | * freeze_workqueues_busy - are freezable workqueues still busy? | |
3632 | * | |
3633 | * Check whether freezing is complete. This function must be called | |
3634 | * between freeze_workqueues_begin() and thaw_workqueues(). | |
3635 | * | |
3636 | * CONTEXT: | |
3637 | * Grabs and releases workqueue_lock. | |
3638 | * | |
3639 | * RETURNS: | |
3640 | * %true if some freezable workqueues are still busy. %false if freezing | |
3641 | * is complete. | |
3642 | */ | |
3643 | bool freeze_workqueues_busy(void) | |
3644 | { | |
3645 | unsigned int cpu; | |
3646 | bool busy = false; | |
3647 | ||
3648 | spin_lock(&workqueue_lock); | |
3649 | ||
3650 | BUG_ON(!workqueue_freezing); | |
3651 | ||
3652 | for_each_gcwq_cpu(cpu) { | |
3653 | struct workqueue_struct *wq; | |
3654 | /* | |
3655 | * nr_active is monotonically decreasing. It's safe | |
3656 | * to peek without lock. | |
3657 | */ | |
3658 | list_for_each_entry(wq, &workqueues, list) { | |
3659 | struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); | |
3660 | ||
3661 | if (!cwq || !(wq->flags & WQ_FREEZABLE)) | |
3662 | continue; | |
3663 | ||
3664 | BUG_ON(cwq->nr_active < 0); | |
3665 | if (cwq->nr_active) { | |
3666 | busy = true; | |
3667 | goto out_unlock; | |
3668 | } | |
3669 | } | |
3670 | } | |
3671 | out_unlock: | |
3672 | spin_unlock(&workqueue_lock); | |
3673 | return busy; | |
3674 | } | |
3675 | ||
3676 | /** | |
3677 | * thaw_workqueues - thaw workqueues | |
3678 | * | |
3679 | * Thaw workqueues. Normal queueing is restored and all collected | |
3680 | * frozen works are transferred to their respective gcwq worklists. | |
3681 | * | |
3682 | * CONTEXT: | |
3683 | * Grabs and releases workqueue_lock and gcwq->lock's. | |
3684 | */ | |
3685 | void thaw_workqueues(void) | |
3686 | { | |
3687 | unsigned int cpu; | |
3688 | ||
3689 | spin_lock(&workqueue_lock); | |
3690 | ||
3691 | if (!workqueue_freezing) | |
3692 | goto out_unlock; | |
3693 | ||
3694 | for_each_gcwq_cpu(cpu) { | |
3695 | struct global_cwq *gcwq = get_gcwq(cpu); | |
3696 | struct worker_pool *pool; | |
3697 | struct workqueue_struct *wq; | |
3698 | ||
3699 | spin_lock_irq(&gcwq->lock); | |
3700 | ||
3701 | BUG_ON(!(gcwq->flags & GCWQ_FREEZING)); | |
3702 | gcwq->flags &= ~GCWQ_FREEZING; | |
3703 | ||
3704 | list_for_each_entry(wq, &workqueues, list) { | |
3705 | struct cpu_workqueue_struct *cwq = get_cwq(cpu, wq); | |
3706 | ||
3707 | if (!cwq || !(wq->flags & WQ_FREEZABLE)) | |
3708 | continue; | |
3709 | ||
3710 | /* restore max_active and repopulate worklist */ | |
3711 | cwq->max_active = wq->saved_max_active; | |
3712 | ||
3713 | while (!list_empty(&cwq->delayed_works) && | |
3714 | cwq->nr_active < cwq->max_active) | |
3715 | cwq_activate_first_delayed(cwq); | |
3716 | } | |
3717 | ||
3718 | for_each_worker_pool(pool, gcwq) | |
3719 | wake_up_worker(pool); | |
3720 | ||
3721 | spin_unlock_irq(&gcwq->lock); | |
3722 | } | |
3723 | ||
3724 | workqueue_freezing = false; | |
3725 | out_unlock: | |
3726 | spin_unlock(&workqueue_lock); | |
3727 | } | |
3728 | #endif /* CONFIG_FREEZER */ | |
3729 | ||
3730 | static int __init init_workqueues(void) | |
3731 | { | |
3732 | unsigned int cpu; | |
3733 | int i; | |
3734 | ||
3735 | /* make sure we have enough bits for OFFQ CPU number */ | |
3736 | BUILD_BUG_ON((1LU << (BITS_PER_LONG - WORK_OFFQ_CPU_SHIFT)) < | |
3737 | WORK_CPU_LAST); | |
3738 | ||
3739 | cpu_notifier(workqueue_cpu_up_callback, CPU_PRI_WORKQUEUE_UP); | |
3740 | cpu_notifier(workqueue_cpu_down_callback, CPU_PRI_WORKQUEUE_DOWN); | |
3741 | ||
3742 | /* initialize gcwqs */ | |
3743 | for_each_gcwq_cpu(cpu) { | |
3744 | struct global_cwq *gcwq = get_gcwq(cpu); | |
3745 | struct worker_pool *pool; | |
3746 | ||
3747 | spin_lock_init(&gcwq->lock); | |
3748 | gcwq->cpu = cpu; | |
3749 | gcwq->flags |= GCWQ_DISASSOCIATED; | |
3750 | ||
3751 | for (i = 0; i < BUSY_WORKER_HASH_SIZE; i++) | |
3752 | INIT_HLIST_HEAD(&gcwq->busy_hash[i]); | |
3753 | ||
3754 | for_each_worker_pool(pool, gcwq) { | |
3755 | pool->gcwq = gcwq; | |
3756 | INIT_LIST_HEAD(&pool->worklist); | |
3757 | INIT_LIST_HEAD(&pool->idle_list); | |
3758 | ||
3759 | init_timer_deferrable(&pool->idle_timer); | |
3760 | pool->idle_timer.function = idle_worker_timeout; | |
3761 | pool->idle_timer.data = (unsigned long)pool; | |
3762 | ||
3763 | setup_timer(&pool->mayday_timer, gcwq_mayday_timeout, | |
3764 | (unsigned long)pool); | |
3765 | ||
3766 | mutex_init(&pool->manager_mutex); | |
3767 | ida_init(&pool->worker_ida); | |
3768 | } | |
3769 | ||
3770 | init_waitqueue_head(&gcwq->rebind_hold); | |
3771 | } | |
3772 | ||
3773 | /* create the initial worker */ | |
3774 | for_each_online_gcwq_cpu(cpu) { | |
3775 | struct global_cwq *gcwq = get_gcwq(cpu); | |
3776 | struct worker_pool *pool; | |
3777 | ||
3778 | if (cpu != WORK_CPU_UNBOUND) | |
3779 | gcwq->flags &= ~GCWQ_DISASSOCIATED; | |
3780 | ||
3781 | for_each_worker_pool(pool, gcwq) { | |
3782 | struct worker *worker; | |
3783 | ||
3784 | worker = create_worker(pool); | |
3785 | BUG_ON(!worker); | |
3786 | spin_lock_irq(&gcwq->lock); | |
3787 | start_worker(worker); | |
3788 | spin_unlock_irq(&gcwq->lock); | |
3789 | } | |
3790 | } | |
3791 | ||
3792 | system_wq = alloc_workqueue("events", 0, 0); | |
3793 | system_long_wq = alloc_workqueue("events_long", 0, 0); | |
3794 | system_nrt_wq = alloc_workqueue("events_nrt", WQ_NON_REENTRANT, 0); | |
3795 | system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND, | |
3796 | WQ_UNBOUND_MAX_ACTIVE); | |
3797 | system_freezable_wq = alloc_workqueue("events_freezable", | |
3798 | WQ_FREEZABLE, 0); | |
3799 | system_nrt_freezable_wq = alloc_workqueue("events_nrt_freezable", | |
3800 | WQ_NON_REENTRANT | WQ_FREEZABLE, 0); | |
3801 | BUG_ON(!system_wq || !system_long_wq || !system_nrt_wq || | |
3802 | !system_unbound_wq || !system_freezable_wq || | |
3803 | !system_nrt_freezable_wq); | |
3804 | return 0; | |
3805 | } | |
3806 | early_initcall(init_workqueues); |