xref: /linux-6.15/include/linux/workqueue.h (revision 08559657)
1 /*
2  * workqueue.h --- work queue handling for Linux.
3  */
4 
5 #ifndef _LINUX_WORKQUEUE_H
6 #define _LINUX_WORKQUEUE_H
7 
8 #include <linux/timer.h>
9 #include <linux/linkage.h>
10 #include <linux/bitops.h>
11 #include <linux/lockdep.h>
12 #include <linux/threads.h>
13 #include <linux/atomic.h>
14 #include <linux/cpumask.h>
15 
16 struct workqueue_struct;
17 
18 struct work_struct;
19 typedef void (*work_func_t)(struct work_struct *work);
20 void delayed_work_timer_fn(unsigned long __data);
21 
22 /*
23  * The first word is the work queue pointer and the flags rolled into
24  * one
25  */
26 #define work_data_bits(work) ((unsigned long *)(&(work)->data))
27 
28 enum {
29 	WORK_STRUCT_PENDING_BIT	= 0,	/* work item is pending execution */
30 	WORK_STRUCT_DELAYED_BIT	= 1,	/* work item is delayed */
31 	WORK_STRUCT_PWQ_BIT	= 2,	/* data points to pwq */
32 	WORK_STRUCT_LINKED_BIT	= 3,	/* next work is linked to this one */
33 #ifdef CONFIG_DEBUG_OBJECTS_WORK
34 	WORK_STRUCT_STATIC_BIT	= 4,	/* static initializer (debugobjects) */
35 	WORK_STRUCT_COLOR_SHIFT	= 5,	/* color for workqueue flushing */
36 #else
37 	WORK_STRUCT_COLOR_SHIFT	= 4,	/* color for workqueue flushing */
38 #endif
39 
40 	WORK_STRUCT_COLOR_BITS	= 4,
41 
42 	WORK_STRUCT_PENDING	= 1 << WORK_STRUCT_PENDING_BIT,
43 	WORK_STRUCT_DELAYED	= 1 << WORK_STRUCT_DELAYED_BIT,
44 	WORK_STRUCT_PWQ		= 1 << WORK_STRUCT_PWQ_BIT,
45 	WORK_STRUCT_LINKED	= 1 << WORK_STRUCT_LINKED_BIT,
46 #ifdef CONFIG_DEBUG_OBJECTS_WORK
47 	WORK_STRUCT_STATIC	= 1 << WORK_STRUCT_STATIC_BIT,
48 #else
49 	WORK_STRUCT_STATIC	= 0,
50 #endif
51 
52 	/*
53 	 * The last color is no color used for works which don't
54 	 * participate in workqueue flushing.
55 	 */
56 	WORK_NR_COLORS		= (1 << WORK_STRUCT_COLOR_BITS) - 1,
57 	WORK_NO_COLOR		= WORK_NR_COLORS,
58 
59 	/* not bound to any CPU, prefer the local CPU */
60 	WORK_CPU_UNBOUND	= NR_CPUS,
61 
62 	/*
63 	 * Reserve 7 bits off of pwq pointer w/ debugobjects turned off.
64 	 * This makes pwqs aligned to 256 bytes and allows 15 workqueue
65 	 * flush colors.
66 	 */
67 	WORK_STRUCT_FLAG_BITS	= WORK_STRUCT_COLOR_SHIFT +
68 				  WORK_STRUCT_COLOR_BITS,
69 
70 	/* data contains off-queue information when !WORK_STRUCT_PWQ */
71 	WORK_OFFQ_FLAG_BASE	= WORK_STRUCT_COLOR_SHIFT,
72 
73 	__WORK_OFFQ_CANCELING	= WORK_OFFQ_FLAG_BASE,
74 	WORK_OFFQ_CANCELING	= (1 << __WORK_OFFQ_CANCELING),
75 
76 	/*
77 	 * When a work item is off queue, its high bits point to the last
78 	 * pool it was on.  Cap at 31 bits and use the highest number to
79 	 * indicate that no pool is associated.
80 	 */
81 	WORK_OFFQ_FLAG_BITS	= 1,
82 	WORK_OFFQ_POOL_SHIFT	= WORK_OFFQ_FLAG_BASE + WORK_OFFQ_FLAG_BITS,
83 	WORK_OFFQ_LEFT		= BITS_PER_LONG - WORK_OFFQ_POOL_SHIFT,
84 	WORK_OFFQ_POOL_BITS	= WORK_OFFQ_LEFT <= 31 ? WORK_OFFQ_LEFT : 31,
85 	WORK_OFFQ_POOL_NONE	= (1LU << WORK_OFFQ_POOL_BITS) - 1,
86 
87 	/* convenience constants */
88 	WORK_STRUCT_FLAG_MASK	= (1UL << WORK_STRUCT_FLAG_BITS) - 1,
89 	WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK,
90 	WORK_STRUCT_NO_POOL	= (unsigned long)WORK_OFFQ_POOL_NONE << WORK_OFFQ_POOL_SHIFT,
91 
92 	/* bit mask for work_busy() return values */
93 	WORK_BUSY_PENDING	= 1 << 0,
94 	WORK_BUSY_RUNNING	= 1 << 1,
95 
96 	/* maximum string length for set_worker_desc() */
97 	WORKER_DESC_LEN		= 24,
98 };
99 
100 struct work_struct {
101 	atomic_long_t data;
102 	struct list_head entry;
103 	work_func_t func;
104 #ifdef CONFIG_LOCKDEP
105 	struct lockdep_map lockdep_map;
106 #endif
107 };
108 
109 #define WORK_DATA_INIT()	ATOMIC_LONG_INIT(WORK_STRUCT_NO_POOL)
110 #define WORK_DATA_STATIC_INIT()	\
111 	ATOMIC_LONG_INIT(WORK_STRUCT_NO_POOL | WORK_STRUCT_STATIC)
112 
113 struct delayed_work {
114 	struct work_struct work;
115 	struct timer_list timer;
116 
117 	/* target workqueue and CPU ->timer uses to queue ->work */
118 	struct workqueue_struct *wq;
119 	int cpu;
120 };
121 
122 /*
123  * A struct for workqueue attributes.  This can be used to change
124  * attributes of an unbound workqueue.
125  *
126  * Unlike other fields, ->no_numa isn't a property of a worker_pool.  It
127  * only modifies how apply_workqueue_attrs() select pools and thus doesn't
128  * participate in pool hash calculations or equality comparisons.
129  */
130 struct workqueue_attrs {
131 	int			nice;		/* nice level */
132 	cpumask_var_t		cpumask;	/* allowed CPUs */
133 	bool			no_numa;	/* disable NUMA affinity */
134 };
135 
136 static inline struct delayed_work *to_delayed_work(struct work_struct *work)
137 {
138 	return container_of(work, struct delayed_work, work);
139 }
140 
141 struct execute_work {
142 	struct work_struct work;
143 };
144 
145 #ifdef CONFIG_LOCKDEP
146 /*
147  * NB: because we have to copy the lockdep_map, setting _key
148  * here is required, otherwise it could get initialised to the
149  * copy of the lockdep_map!
150  */
151 #define __WORK_INIT_LOCKDEP_MAP(n, k) \
152 	.lockdep_map = STATIC_LOCKDEP_MAP_INIT(n, k),
153 #else
154 #define __WORK_INIT_LOCKDEP_MAP(n, k)
155 #endif
156 
157 #define __WORK_INITIALIZER(n, f) {					\
158 	.data = WORK_DATA_STATIC_INIT(),				\
159 	.entry	= { &(n).entry, &(n).entry },				\
160 	.func = (f),							\
161 	__WORK_INIT_LOCKDEP_MAP(#n, &(n))				\
162 	}
163 
164 #define __DELAYED_WORK_INITIALIZER(n, f, tflags) {			\
165 	.work = __WORK_INITIALIZER((n).work, (f)),			\
166 	.timer = __TIMER_INITIALIZER(delayed_work_timer_fn,		\
167 				     0, (unsigned long)&(n),		\
168 				     (tflags) | TIMER_IRQSAFE),		\
169 	}
170 
171 #define DECLARE_WORK(n, f)						\
172 	struct work_struct n = __WORK_INITIALIZER(n, f)
173 
174 #define DECLARE_DELAYED_WORK(n, f)					\
175 	struct delayed_work n = __DELAYED_WORK_INITIALIZER(n, f, 0)
176 
177 #define DECLARE_DEFERRABLE_WORK(n, f)					\
178 	struct delayed_work n = __DELAYED_WORK_INITIALIZER(n, f, TIMER_DEFERRABLE)
179 
180 #ifdef CONFIG_DEBUG_OBJECTS_WORK
181 extern void __init_work(struct work_struct *work, int onstack);
182 extern void destroy_work_on_stack(struct work_struct *work);
183 extern void destroy_delayed_work_on_stack(struct delayed_work *work);
184 static inline unsigned int work_static(struct work_struct *work)
185 {
186 	return *work_data_bits(work) & WORK_STRUCT_STATIC;
187 }
188 #else
189 static inline void __init_work(struct work_struct *work, int onstack) { }
190 static inline void destroy_work_on_stack(struct work_struct *work) { }
191 static inline void destroy_delayed_work_on_stack(struct delayed_work *work) { }
192 static inline unsigned int work_static(struct work_struct *work) { return 0; }
193 #endif
194 
195 /*
196  * initialize all of a work item in one go
197  *
198  * NOTE! No point in using "atomic_long_set()": using a direct
199  * assignment of the work data initializer allows the compiler
200  * to generate better code.
201  */
202 #ifdef CONFIG_LOCKDEP
203 #define __INIT_WORK(_work, _func, _onstack)				\
204 	do {								\
205 		static struct lock_class_key __key;			\
206 									\
207 		__init_work((_work), _onstack);				\
208 		(_work)->data = (atomic_long_t) WORK_DATA_INIT();	\
209 		lockdep_init_map(&(_work)->lockdep_map, #_work, &__key, 0); \
210 		INIT_LIST_HEAD(&(_work)->entry);			\
211 		(_work)->func = (_func);				\
212 	} while (0)
213 #else
214 #define __INIT_WORK(_work, _func, _onstack)				\
215 	do {								\
216 		__init_work((_work), _onstack);				\
217 		(_work)->data = (atomic_long_t) WORK_DATA_INIT();	\
218 		INIT_LIST_HEAD(&(_work)->entry);			\
219 		(_work)->func = (_func);				\
220 	} while (0)
221 #endif
222 
223 #define INIT_WORK(_work, _func)						\
224 	__INIT_WORK((_work), (_func), 0)
225 
226 #define INIT_WORK_ONSTACK(_work, _func)					\
227 	__INIT_WORK((_work), (_func), 1)
228 
229 #define __INIT_DELAYED_WORK(_work, _func, _tflags)			\
230 	do {								\
231 		INIT_WORK(&(_work)->work, (_func));			\
232 		__setup_timer(&(_work)->timer, delayed_work_timer_fn,	\
233 			      (unsigned long)(_work),			\
234 			      (_tflags) | TIMER_IRQSAFE);		\
235 	} while (0)
236 
237 #define __INIT_DELAYED_WORK_ONSTACK(_work, _func, _tflags)		\
238 	do {								\
239 		INIT_WORK_ONSTACK(&(_work)->work, (_func));		\
240 		__setup_timer_on_stack(&(_work)->timer,			\
241 				       delayed_work_timer_fn,		\
242 				       (unsigned long)(_work),		\
243 				       (_tflags) | TIMER_IRQSAFE);	\
244 	} while (0)
245 
246 #define INIT_DELAYED_WORK(_work, _func)					\
247 	__INIT_DELAYED_WORK(_work, _func, 0)
248 
249 #define INIT_DELAYED_WORK_ONSTACK(_work, _func)				\
250 	__INIT_DELAYED_WORK_ONSTACK(_work, _func, 0)
251 
252 #define INIT_DEFERRABLE_WORK(_work, _func)				\
253 	__INIT_DELAYED_WORK(_work, _func, TIMER_DEFERRABLE)
254 
255 #define INIT_DEFERRABLE_WORK_ONSTACK(_work, _func)			\
256 	__INIT_DELAYED_WORK_ONSTACK(_work, _func, TIMER_DEFERRABLE)
257 
258 /**
259  * work_pending - Find out whether a work item is currently pending
260  * @work: The work item in question
261  */
262 #define work_pending(work) \
263 	test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))
264 
265 /**
266  * delayed_work_pending - Find out whether a delayable work item is currently
267  * pending
268  * @w: The work item in question
269  */
270 #define delayed_work_pending(w) \
271 	work_pending(&(w)->work)
272 
273 /*
274  * Workqueue flags and constants.  For details, please refer to
275  * Documentation/workqueue.txt.
276  */
277 enum {
278 	WQ_UNBOUND		= 1 << 1, /* not bound to any cpu */
279 	WQ_FREEZABLE		= 1 << 2, /* freeze during suspend */
280 	WQ_MEM_RECLAIM		= 1 << 3, /* may be used for memory reclaim */
281 	WQ_HIGHPRI		= 1 << 4, /* high priority */
282 	WQ_CPU_INTENSIVE	= 1 << 5, /* cpu intensive workqueue */
283 	WQ_SYSFS		= 1 << 6, /* visible in sysfs, see wq_sysfs_register() */
284 
285 	/*
286 	 * Per-cpu workqueues are generally preferred because they tend to
287 	 * show better performance thanks to cache locality.  Per-cpu
288 	 * workqueues exclude the scheduler from choosing the CPU to
289 	 * execute the worker threads, which has an unfortunate side effect
290 	 * of increasing power consumption.
291 	 *
292 	 * The scheduler considers a CPU idle if it doesn't have any task
293 	 * to execute and tries to keep idle cores idle to conserve power;
294 	 * however, for example, a per-cpu work item scheduled from an
295 	 * interrupt handler on an idle CPU will force the scheduler to
296 	 * excute the work item on that CPU breaking the idleness, which in
297 	 * turn may lead to more scheduling choices which are sub-optimal
298 	 * in terms of power consumption.
299 	 *
300 	 * Workqueues marked with WQ_POWER_EFFICIENT are per-cpu by default
301 	 * but become unbound if workqueue.power_efficient kernel param is
302 	 * specified.  Per-cpu workqueues which are identified to
303 	 * contribute significantly to power-consumption are identified and
304 	 * marked with this flag and enabling the power_efficient mode
305 	 * leads to noticeable power saving at the cost of small
306 	 * performance disadvantage.
307 	 *
308 	 * http://thread.gmane.org/gmane.linux.kernel/1480396
309 	 */
310 	WQ_POWER_EFFICIENT	= 1 << 7,
311 
312 	__WQ_DRAINING		= 1 << 16, /* internal: workqueue is draining */
313 	__WQ_ORDERED		= 1 << 17, /* internal: workqueue is ordered */
314 	__WQ_LEGACY		= 1 << 18, /* internal: create*_workqueue() */
315 
316 	WQ_MAX_ACTIVE		= 512,	  /* I like 512, better ideas? */
317 	WQ_MAX_UNBOUND_PER_CPU	= 4,	  /* 4 * #cpus for unbound wq */
318 	WQ_DFL_ACTIVE		= WQ_MAX_ACTIVE / 2,
319 };
320 
321 /* unbound wq's aren't per-cpu, scale max_active according to #cpus */
322 #define WQ_UNBOUND_MAX_ACTIVE	\
323 	max_t(int, WQ_MAX_ACTIVE, num_possible_cpus() * WQ_MAX_UNBOUND_PER_CPU)
324 
325 /*
326  * System-wide workqueues which are always present.
327  *
328  * system_wq is the one used by schedule[_delayed]_work[_on]().
329  * Multi-CPU multi-threaded.  There are users which expect relatively
330  * short queue flush time.  Don't queue works which can run for too
331  * long.
332  *
333  * system_highpri_wq is similar to system_wq but for work items which
334  * require WQ_HIGHPRI.
335  *
336  * system_long_wq is similar to system_wq but may host long running
337  * works.  Queue flushing might take relatively long.
338  *
339  * system_unbound_wq is unbound workqueue.  Workers are not bound to
340  * any specific CPU, not concurrency managed, and all queued works are
341  * executed immediately as long as max_active limit is not reached and
342  * resources are available.
343  *
344  * system_freezable_wq is equivalent to system_wq except that it's
345  * freezable.
346  *
347  * *_power_efficient_wq are inclined towards saving power and converted
348  * into WQ_UNBOUND variants if 'wq_power_efficient' is enabled; otherwise,
349  * they are same as their non-power-efficient counterparts - e.g.
350  * system_power_efficient_wq is identical to system_wq if
351  * 'wq_power_efficient' is disabled.  See WQ_POWER_EFFICIENT for more info.
352  */
353 extern struct workqueue_struct *system_wq;
354 extern struct workqueue_struct *system_highpri_wq;
355 extern struct workqueue_struct *system_long_wq;
356 extern struct workqueue_struct *system_unbound_wq;
357 extern struct workqueue_struct *system_freezable_wq;
358 extern struct workqueue_struct *system_power_efficient_wq;
359 extern struct workqueue_struct *system_freezable_power_efficient_wq;
360 
361 extern struct workqueue_struct *
362 __alloc_workqueue_key(const char *fmt, unsigned int flags, int max_active,
363 	struct lock_class_key *key, const char *lock_name, ...) __printf(1, 6);
364 
365 /**
366  * alloc_workqueue - allocate a workqueue
367  * @fmt: printf format for the name of the workqueue
368  * @flags: WQ_* flags
369  * @max_active: max in-flight work items, 0 for default
370  * @args...: args for @fmt
371  *
372  * Allocate a workqueue with the specified parameters.  For detailed
373  * information on WQ_* flags, please refer to Documentation/workqueue.txt.
374  *
375  * The __lock_name macro dance is to guarantee that single lock_class_key
376  * doesn't end up with different namesm, which isn't allowed by lockdep.
377  *
378  * RETURNS:
379  * Pointer to the allocated workqueue on success, %NULL on failure.
380  */
381 #ifdef CONFIG_LOCKDEP
382 #define alloc_workqueue(fmt, flags, max_active, args...)		\
383 ({									\
384 	static struct lock_class_key __key;				\
385 	const char *__lock_name;					\
386 									\
387 	__lock_name = #fmt#args;					\
388 									\
389 	__alloc_workqueue_key((fmt), (flags), (max_active),		\
390 			      &__key, __lock_name, ##args);		\
391 })
392 #else
393 #define alloc_workqueue(fmt, flags, max_active, args...)		\
394 	__alloc_workqueue_key((fmt), (flags), (max_active),		\
395 			      NULL, NULL, ##args)
396 #endif
397 
398 /**
399  * alloc_ordered_workqueue - allocate an ordered workqueue
400  * @fmt: printf format for the name of the workqueue
401  * @flags: WQ_* flags (only WQ_FREEZABLE and WQ_MEM_RECLAIM are meaningful)
402  * @args...: args for @fmt
403  *
404  * Allocate an ordered workqueue.  An ordered workqueue executes at
405  * most one work item at any given time in the queued order.  They are
406  * implemented as unbound workqueues with @max_active of one.
407  *
408  * RETURNS:
409  * Pointer to the allocated workqueue on success, %NULL on failure.
410  */
411 #define alloc_ordered_workqueue(fmt, flags, args...)			\
412 	alloc_workqueue(fmt, WQ_UNBOUND | __WQ_ORDERED | (flags), 1, ##args)
413 
414 #define create_workqueue(name)						\
415 	alloc_workqueue("%s", __WQ_LEGACY | WQ_MEM_RECLAIM, 1, (name))
416 #define create_freezable_workqueue(name)				\
417 	alloc_workqueue("%s", __WQ_LEGACY | WQ_FREEZABLE | WQ_UNBOUND |	\
418 			WQ_MEM_RECLAIM, 1, (name))
419 #define create_singlethread_workqueue(name)				\
420 	alloc_ordered_workqueue("%s", __WQ_LEGACY | WQ_MEM_RECLAIM, name)
421 
422 extern void destroy_workqueue(struct workqueue_struct *wq);
423 
424 struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask);
425 void free_workqueue_attrs(struct workqueue_attrs *attrs);
426 int apply_workqueue_attrs(struct workqueue_struct *wq,
427 			  const struct workqueue_attrs *attrs);
428 int workqueue_set_unbound_cpumask(cpumask_var_t cpumask);
429 
430 extern bool queue_work_on(int cpu, struct workqueue_struct *wq,
431 			struct work_struct *work);
432 extern bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
433 			struct delayed_work *work, unsigned long delay);
434 extern bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
435 			struct delayed_work *dwork, unsigned long delay);
436 
437 extern void flush_workqueue(struct workqueue_struct *wq);
438 extern void drain_workqueue(struct workqueue_struct *wq);
439 
440 extern int schedule_on_each_cpu(work_func_t func);
441 
442 int execute_in_process_context(work_func_t fn, struct execute_work *);
443 
444 extern bool flush_work(struct work_struct *work);
445 extern bool cancel_work_sync(struct work_struct *work);
446 
447 extern bool flush_delayed_work(struct delayed_work *dwork);
448 extern bool cancel_delayed_work(struct delayed_work *dwork);
449 extern bool cancel_delayed_work_sync(struct delayed_work *dwork);
450 
451 extern void workqueue_set_max_active(struct workqueue_struct *wq,
452 				     int max_active);
453 extern bool current_is_workqueue_rescuer(void);
454 extern bool workqueue_congested(int cpu, struct workqueue_struct *wq);
455 extern unsigned int work_busy(struct work_struct *work);
456 extern __printf(1, 2) void set_worker_desc(const char *fmt, ...);
457 extern void print_worker_info(const char *log_lvl, struct task_struct *task);
458 extern void show_workqueue_state(void);
459 
460 /**
461  * queue_work - queue work on a workqueue
462  * @wq: workqueue to use
463  * @work: work to queue
464  *
465  * Returns %false if @work was already on a queue, %true otherwise.
466  *
467  * We queue the work to the CPU on which it was submitted, but if the CPU dies
468  * it can be processed by another CPU.
469  */
470 static inline bool queue_work(struct workqueue_struct *wq,
471 			      struct work_struct *work)
472 {
473 	return queue_work_on(WORK_CPU_UNBOUND, wq, work);
474 }
475 
476 /**
477  * queue_delayed_work - queue work on a workqueue after delay
478  * @wq: workqueue to use
479  * @dwork: delayable work to queue
480  * @delay: number of jiffies to wait before queueing
481  *
482  * Equivalent to queue_delayed_work_on() but tries to use the local CPU.
483  */
484 static inline bool queue_delayed_work(struct workqueue_struct *wq,
485 				      struct delayed_work *dwork,
486 				      unsigned long delay)
487 {
488 	return queue_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay);
489 }
490 
491 /**
492  * mod_delayed_work - modify delay of or queue a delayed work
493  * @wq: workqueue to use
494  * @dwork: work to queue
495  * @delay: number of jiffies to wait before queueing
496  *
497  * mod_delayed_work_on() on local CPU.
498  */
499 static inline bool mod_delayed_work(struct workqueue_struct *wq,
500 				    struct delayed_work *dwork,
501 				    unsigned long delay)
502 {
503 	return mod_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay);
504 }
505 
506 /**
507  * schedule_work_on - put work task on a specific cpu
508  * @cpu: cpu to put the work task on
509  * @work: job to be done
510  *
511  * This puts a job on a specific cpu
512  */
513 static inline bool schedule_work_on(int cpu, struct work_struct *work)
514 {
515 	return queue_work_on(cpu, system_wq, work);
516 }
517 
518 /**
519  * schedule_work - put work task in global workqueue
520  * @work: job to be done
521  *
522  * Returns %false if @work was already on the kernel-global workqueue and
523  * %true otherwise.
524  *
525  * This puts a job in the kernel-global workqueue if it was not already
526  * queued and leaves it in the same position on the kernel-global
527  * workqueue otherwise.
528  */
529 static inline bool schedule_work(struct work_struct *work)
530 {
531 	return queue_work(system_wq, work);
532 }
533 
534 /**
535  * flush_scheduled_work - ensure that any scheduled work has run to completion.
536  *
537  * Forces execution of the kernel-global workqueue and blocks until its
538  * completion.
539  *
540  * Think twice before calling this function!  It's very easy to get into
541  * trouble if you don't take great care.  Either of the following situations
542  * will lead to deadlock:
543  *
544  *	One of the work items currently on the workqueue needs to acquire
545  *	a lock held by your code or its caller.
546  *
547  *	Your code is running in the context of a work routine.
548  *
549  * They will be detected by lockdep when they occur, but the first might not
550  * occur very often.  It depends on what work items are on the workqueue and
551  * what locks they need, which you have no control over.
552  *
553  * In most situations flushing the entire workqueue is overkill; you merely
554  * need to know that a particular work item isn't queued and isn't running.
555  * In such cases you should use cancel_delayed_work_sync() or
556  * cancel_work_sync() instead.
557  */
558 static inline void flush_scheduled_work(void)
559 {
560 	flush_workqueue(system_wq);
561 }
562 
563 /**
564  * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
565  * @cpu: cpu to use
566  * @dwork: job to be done
567  * @delay: number of jiffies to wait
568  *
569  * After waiting for a given time this puts a job in the kernel-global
570  * workqueue on the specified CPU.
571  */
572 static inline bool schedule_delayed_work_on(int cpu, struct delayed_work *dwork,
573 					    unsigned long delay)
574 {
575 	return queue_delayed_work_on(cpu, system_wq, dwork, delay);
576 }
577 
578 /**
579  * schedule_delayed_work - put work task in global workqueue after delay
580  * @dwork: job to be done
581  * @delay: number of jiffies to wait or 0 for immediate execution
582  *
583  * After waiting for a given time this puts a job in the kernel-global
584  * workqueue.
585  */
586 static inline bool schedule_delayed_work(struct delayed_work *dwork,
587 					 unsigned long delay)
588 {
589 	return queue_delayed_work(system_wq, dwork, delay);
590 }
591 
592 /**
593  * keventd_up - is workqueue initialized yet?
594  */
595 static inline bool keventd_up(void)
596 {
597 	return system_wq != NULL;
598 }
599 
600 #ifndef CONFIG_SMP
601 static inline long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
602 {
603 	return fn(arg);
604 }
605 #else
606 long work_on_cpu(int cpu, long (*fn)(void *), void *arg);
607 #endif /* CONFIG_SMP */
608 
609 #ifdef CONFIG_FREEZER
610 extern void freeze_workqueues_begin(void);
611 extern bool freeze_workqueues_busy(void);
612 extern void thaw_workqueues(void);
613 #endif /* CONFIG_FREEZER */
614 
615 #ifdef CONFIG_SYSFS
616 int workqueue_sysfs_register(struct workqueue_struct *wq);
617 #else	/* CONFIG_SYSFS */
618 static inline int workqueue_sysfs_register(struct workqueue_struct *wq)
619 { return 0; }
620 #endif	/* CONFIG_SYSFS */
621 
622 #ifdef CONFIG_WQ_WATCHDOG
623 void wq_watchdog_touch(int cpu);
624 #else	/* CONFIG_WQ_WATCHDOG */
625 static inline void wq_watchdog_touch(int cpu) { }
626 #endif	/* CONFIG_WQ_WATCHDOG */
627 
628 #endif
629