workqueue.c 106 KB

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