1 /* SPDX-License-Identifier: GPL-2.0 */
3 * workqueue.h --- work queue handling for Linux.
6 #ifndef _LINUX_WORKQUEUE_H
7 #define _LINUX_WORKQUEUE_H
9 #include <linux/timer.h>
10 #include <linux/linkage.h>
11 #include <linux/bitops.h>
12 #include <linux/lockdep.h>
13 #include <linux/threads.h>
14 #include <linux/atomic.h>
15 #include <linux/cpumask.h>
17 struct workqueue_struct;
20 typedef void (*work_func_t)(struct work_struct *work);
21 void delayed_work_timer_fn(struct timer_list *t);
24 * The first word is the work queue pointer and the flags rolled into
27 #define work_data_bits(work) ((unsigned long *)(&(work)->data))
30 WORK_STRUCT_PENDING_BIT = 0, /* work item is pending execution */
31 WORK_STRUCT_DELAYED_BIT = 1, /* work item is delayed */
32 WORK_STRUCT_PWQ_BIT = 2, /* data points to pwq */
33 WORK_STRUCT_LINKED_BIT = 3, /* next work is linked to this one */
34 #ifdef CONFIG_DEBUG_OBJECTS_WORK
35 WORK_STRUCT_STATIC_BIT = 4, /* static initializer (debugobjects) */
36 WORK_STRUCT_COLOR_SHIFT = 5, /* color for workqueue flushing */
38 WORK_STRUCT_COLOR_SHIFT = 4, /* color for workqueue flushing */
41 WORK_STRUCT_COLOR_BITS = 4,
43 WORK_STRUCT_PENDING = 1 << WORK_STRUCT_PENDING_BIT,
44 WORK_STRUCT_DELAYED = 1 << WORK_STRUCT_DELAYED_BIT,
45 WORK_STRUCT_PWQ = 1 << WORK_STRUCT_PWQ_BIT,
46 WORK_STRUCT_LINKED = 1 << WORK_STRUCT_LINKED_BIT,
47 #ifdef CONFIG_DEBUG_OBJECTS_WORK
48 WORK_STRUCT_STATIC = 1 << WORK_STRUCT_STATIC_BIT,
50 WORK_STRUCT_STATIC = 0,
54 * The last color is no color used for works which don't
55 * participate in workqueue flushing.
57 WORK_NR_COLORS = (1 << WORK_STRUCT_COLOR_BITS) - 1,
58 WORK_NO_COLOR = WORK_NR_COLORS,
60 /* not bound to any CPU, prefer the local CPU */
61 WORK_CPU_UNBOUND = NR_CPUS,
64 * Reserve 7 bits off of pwq pointer w/ debugobjects turned off.
65 * This makes pwqs aligned to 256 bytes and allows 15 workqueue
68 WORK_STRUCT_FLAG_BITS = WORK_STRUCT_COLOR_SHIFT +
69 WORK_STRUCT_COLOR_BITS,
71 /* data contains off-queue information when !WORK_STRUCT_PWQ */
72 WORK_OFFQ_FLAG_BASE = WORK_STRUCT_COLOR_SHIFT,
74 __WORK_OFFQ_CANCELING = WORK_OFFQ_FLAG_BASE,
75 WORK_OFFQ_CANCELING = (1 << __WORK_OFFQ_CANCELING),
78 * When a work item is off queue, its high bits point to the last
79 * pool it was on. Cap at 31 bits and use the highest number to
80 * indicate that no pool is associated.
82 WORK_OFFQ_FLAG_BITS = 1,
83 WORK_OFFQ_POOL_SHIFT = WORK_OFFQ_FLAG_BASE + WORK_OFFQ_FLAG_BITS,
84 WORK_OFFQ_LEFT = BITS_PER_LONG - WORK_OFFQ_POOL_SHIFT,
85 WORK_OFFQ_POOL_BITS = WORK_OFFQ_LEFT <= 31 ? WORK_OFFQ_LEFT : 31,
86 WORK_OFFQ_POOL_NONE = (1LU << WORK_OFFQ_POOL_BITS) - 1,
88 /* convenience constants */
89 WORK_STRUCT_FLAG_MASK = (1UL << WORK_STRUCT_FLAG_BITS) - 1,
90 WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK,
91 WORK_STRUCT_NO_POOL = (unsigned long)WORK_OFFQ_POOL_NONE << WORK_OFFQ_POOL_SHIFT,
93 /* bit mask for work_busy() return values */
94 WORK_BUSY_PENDING = 1 << 0,
95 WORK_BUSY_RUNNING = 1 << 1,
97 /* maximum string length for set_worker_desc() */
103 struct list_head entry;
105 #ifdef CONFIG_LOCKDEP
106 struct lockdep_map lockdep_map;
110 #define WORK_DATA_INIT() ATOMIC_LONG_INIT((unsigned long)WORK_STRUCT_NO_POOL)
111 #define WORK_DATA_STATIC_INIT() \
112 ATOMIC_LONG_INIT((unsigned long)(WORK_STRUCT_NO_POOL | WORK_STRUCT_STATIC))
114 struct delayed_work {
115 struct work_struct work;
116 struct timer_list timer;
118 /* target workqueue and CPU ->timer uses to queue ->work */
119 struct workqueue_struct *wq;
124 * struct workqueue_attrs - A struct for workqueue attributes.
126 * This can be used to change attributes of an unbound workqueue.
128 struct workqueue_attrs {
135 * @cpumask: allowed CPUs
137 cpumask_var_t cpumask;
140 * @no_numa: disable NUMA affinity
142 * Unlike other fields, ``no_numa`` isn't a property of a worker_pool. It
143 * only modifies how :c:func:`apply_workqueue_attrs` select pools and thus
144 * doesn't participate in pool hash calculations or equality comparisons.
149 static inline struct delayed_work *to_delayed_work(struct work_struct *work)
151 return container_of(work, struct delayed_work, work);
154 struct execute_work {
155 struct work_struct work;
158 #ifdef CONFIG_LOCKDEP
160 * NB: because we have to copy the lockdep_map, setting _key
161 * here is required, otherwise it could get initialised to the
162 * copy of the lockdep_map!
164 #define __WORK_INIT_LOCKDEP_MAP(n, k) \
165 .lockdep_map = STATIC_LOCKDEP_MAP_INIT(n, k),
167 #define __WORK_INIT_LOCKDEP_MAP(n, k)
170 #define __WORK_INITIALIZER(n, f) { \
171 .data = WORK_DATA_STATIC_INIT(), \
172 .entry = { &(n).entry, &(n).entry }, \
174 __WORK_INIT_LOCKDEP_MAP(#n, &(n)) \
177 #define __DELAYED_WORK_INITIALIZER(n, f, tflags) { \
178 .work = __WORK_INITIALIZER((n).work, (f)), \
179 .timer = __TIMER_INITIALIZER((TIMER_FUNC_TYPE)delayed_work_timer_fn,\
180 (TIMER_DATA_TYPE)&(n.timer), \
181 (tflags) | TIMER_IRQSAFE), \
184 #define DECLARE_WORK(n, f) \
185 struct work_struct n = __WORK_INITIALIZER(n, f)
187 #define DECLARE_DELAYED_WORK(n, f) \
188 struct delayed_work n = __DELAYED_WORK_INITIALIZER(n, f, 0)
190 #define DECLARE_DEFERRABLE_WORK(n, f) \
191 struct delayed_work n = __DELAYED_WORK_INITIALIZER(n, f, TIMER_DEFERRABLE)
193 #ifdef CONFIG_DEBUG_OBJECTS_WORK
194 extern void __init_work(struct work_struct *work, int onstack);
195 extern void destroy_work_on_stack(struct work_struct *work);
196 extern void destroy_delayed_work_on_stack(struct delayed_work *work);
197 static inline unsigned int work_static(struct work_struct *work)
199 return *work_data_bits(work) & WORK_STRUCT_STATIC;
202 static inline void __init_work(struct work_struct *work, int onstack) { }
203 static inline void destroy_work_on_stack(struct work_struct *work) { }
204 static inline void destroy_delayed_work_on_stack(struct delayed_work *work) { }
205 static inline unsigned int work_static(struct work_struct *work) { return 0; }
209 * initialize all of a work item in one go
211 * NOTE! No point in using "atomic_long_set()": using a direct
212 * assignment of the work data initializer allows the compiler
213 * to generate better code.
215 #ifdef CONFIG_LOCKDEP
216 #define __INIT_WORK(_work, _func, _onstack) \
218 static struct lock_class_key __key; \
220 __init_work((_work), _onstack); \
221 (_work)->data = (atomic_long_t) WORK_DATA_INIT(); \
222 lockdep_init_map(&(_work)->lockdep_map, "(work_completion)"#_work, &__key, 0); \
223 INIT_LIST_HEAD(&(_work)->entry); \
224 (_work)->func = (_func); \
227 #define __INIT_WORK(_work, _func, _onstack) \
229 __init_work((_work), _onstack); \
230 (_work)->data = (atomic_long_t) WORK_DATA_INIT(); \
231 INIT_LIST_HEAD(&(_work)->entry); \
232 (_work)->func = (_func); \
236 #define INIT_WORK(_work, _func) \
237 __INIT_WORK((_work), (_func), 0)
239 #define INIT_WORK_ONSTACK(_work, _func) \
240 __INIT_WORK((_work), (_func), 1)
242 #define __INIT_DELAYED_WORK(_work, _func, _tflags) \
244 INIT_WORK(&(_work)->work, (_func)); \
245 __setup_timer(&(_work)->timer, \
246 (TIMER_FUNC_TYPE)delayed_work_timer_fn, \
247 (TIMER_DATA_TYPE)&(_work)->timer, \
248 (_tflags) | TIMER_IRQSAFE); \
251 #define __INIT_DELAYED_WORK_ONSTACK(_work, _func, _tflags) \
253 INIT_WORK_ONSTACK(&(_work)->work, (_func)); \
254 __setup_timer_on_stack(&(_work)->timer, \
255 (TIMER_FUNC_TYPE)delayed_work_timer_fn,\
256 (TIMER_DATA_TYPE)&(_work)->timer,\
257 (_tflags) | TIMER_IRQSAFE); \
260 #define INIT_DELAYED_WORK(_work, _func) \
261 __INIT_DELAYED_WORK(_work, _func, 0)
263 #define INIT_DELAYED_WORK_ONSTACK(_work, _func) \
264 __INIT_DELAYED_WORK_ONSTACK(_work, _func, 0)
266 #define INIT_DEFERRABLE_WORK(_work, _func) \
267 __INIT_DELAYED_WORK(_work, _func, TIMER_DEFERRABLE)
269 #define INIT_DEFERRABLE_WORK_ONSTACK(_work, _func) \
270 __INIT_DELAYED_WORK_ONSTACK(_work, _func, TIMER_DEFERRABLE)
273 * work_pending - Find out whether a work item is currently pending
274 * @work: The work item in question
276 #define work_pending(work) \
277 test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))
280 * delayed_work_pending - Find out whether a delayable work item is currently
282 * @w: The work item in question
284 #define delayed_work_pending(w) \
285 work_pending(&(w)->work)
288 * Workqueue flags and constants. For details, please refer to
289 * Documentation/core-api/workqueue.rst.
292 WQ_UNBOUND = 1 << 1, /* not bound to any cpu */
293 WQ_FREEZABLE = 1 << 2, /* freeze during suspend */
294 WQ_MEM_RECLAIM = 1 << 3, /* may be used for memory reclaim */
295 WQ_HIGHPRI = 1 << 4, /* high priority */
296 WQ_CPU_INTENSIVE = 1 << 5, /* cpu intensive workqueue */
297 WQ_SYSFS = 1 << 6, /* visible in sysfs, see wq_sysfs_register() */
300 * Per-cpu workqueues are generally preferred because they tend to
301 * show better performance thanks to cache locality. Per-cpu
302 * workqueues exclude the scheduler from choosing the CPU to
303 * execute the worker threads, which has an unfortunate side effect
304 * of increasing power consumption.
306 * The scheduler considers a CPU idle if it doesn't have any task
307 * to execute and tries to keep idle cores idle to conserve power;
308 * however, for example, a per-cpu work item scheduled from an
309 * interrupt handler on an idle CPU will force the scheduler to
310 * excute the work item on that CPU breaking the idleness, which in
311 * turn may lead to more scheduling choices which are sub-optimal
312 * in terms of power consumption.
314 * Workqueues marked with WQ_POWER_EFFICIENT are per-cpu by default
315 * but become unbound if workqueue.power_efficient kernel param is
316 * specified. Per-cpu workqueues which are identified to
317 * contribute significantly to power-consumption are identified and
318 * marked with this flag and enabling the power_efficient mode
319 * leads to noticeable power saving at the cost of small
320 * performance disadvantage.
322 * http://thread.gmane.org/gmane.linux.kernel/1480396
324 WQ_POWER_EFFICIENT = 1 << 7,
326 __WQ_DRAINING = 1 << 16, /* internal: workqueue is draining */
327 __WQ_ORDERED = 1 << 17, /* internal: workqueue is ordered */
328 __WQ_LEGACY = 1 << 18, /* internal: create*_workqueue() */
329 __WQ_ORDERED_EXPLICIT = 1 << 19, /* internal: alloc_ordered_workqueue() */
331 WQ_MAX_ACTIVE = 512, /* I like 512, better ideas? */
332 WQ_MAX_UNBOUND_PER_CPU = 4, /* 4 * #cpus for unbound wq */
333 WQ_DFL_ACTIVE = WQ_MAX_ACTIVE / 2,
336 /* unbound wq's aren't per-cpu, scale max_active according to #cpus */
337 #define WQ_UNBOUND_MAX_ACTIVE \
338 max_t(int, WQ_MAX_ACTIVE, num_possible_cpus() * WQ_MAX_UNBOUND_PER_CPU)
341 * System-wide workqueues which are always present.
343 * system_wq is the one used by schedule[_delayed]_work[_on]().
344 * Multi-CPU multi-threaded. There are users which expect relatively
345 * short queue flush time. Don't queue works which can run for too
348 * system_highpri_wq is similar to system_wq but for work items which
349 * require WQ_HIGHPRI.
351 * system_long_wq is similar to system_wq but may host long running
352 * works. Queue flushing might take relatively long.
354 * system_unbound_wq is unbound workqueue. Workers are not bound to
355 * any specific CPU, not concurrency managed, and all queued works are
356 * executed immediately as long as max_active limit is not reached and
357 * resources are available.
359 * system_freezable_wq is equivalent to system_wq except that it's
362 * *_power_efficient_wq are inclined towards saving power and converted
363 * into WQ_UNBOUND variants if 'wq_power_efficient' is enabled; otherwise,
364 * they are same as their non-power-efficient counterparts - e.g.
365 * system_power_efficient_wq is identical to system_wq if
366 * 'wq_power_efficient' is disabled. See WQ_POWER_EFFICIENT for more info.
368 extern struct workqueue_struct *system_wq;
369 extern struct workqueue_struct *system_highpri_wq;
370 extern struct workqueue_struct *system_long_wq;
371 extern struct workqueue_struct *system_unbound_wq;
372 extern struct workqueue_struct *system_freezable_wq;
373 extern struct workqueue_struct *system_power_efficient_wq;
374 extern struct workqueue_struct *system_freezable_power_efficient_wq;
376 extern struct workqueue_struct *
377 __alloc_workqueue_key(const char *fmt, unsigned int flags, int max_active,
378 struct lock_class_key *key, const char *lock_name, ...) __printf(1, 6);
381 * alloc_workqueue - allocate a workqueue
382 * @fmt: printf format for the name of the workqueue
384 * @max_active: max in-flight work items, 0 for default
385 * @args...: args for @fmt
387 * Allocate a workqueue with the specified parameters. For detailed
388 * information on WQ_* flags, please refer to
389 * Documentation/core-api/workqueue.rst.
391 * The __lock_name macro dance is to guarantee that single lock_class_key
392 * doesn't end up with different namesm, which isn't allowed by lockdep.
395 * Pointer to the allocated workqueue on success, %NULL on failure.
397 #ifdef CONFIG_LOCKDEP
398 #define alloc_workqueue(fmt, flags, max_active, args...) \
400 static struct lock_class_key __key; \
401 const char *__lock_name; \
403 __lock_name = "(wq_completion)"#fmt#args; \
405 __alloc_workqueue_key((fmt), (flags), (max_active), \
406 &__key, __lock_name, ##args); \
409 #define alloc_workqueue(fmt, flags, max_active, args...) \
410 __alloc_workqueue_key((fmt), (flags), (max_active), \
415 * alloc_ordered_workqueue - allocate an ordered workqueue
416 * @fmt: printf format for the name of the workqueue
417 * @flags: WQ_* flags (only WQ_FREEZABLE and WQ_MEM_RECLAIM are meaningful)
418 * @args...: args for @fmt
420 * Allocate an ordered workqueue. An ordered workqueue executes at
421 * most one work item at any given time in the queued order. They are
422 * implemented as unbound workqueues with @max_active of one.
425 * Pointer to the allocated workqueue on success, %NULL on failure.
427 #define alloc_ordered_workqueue(fmt, flags, args...) \
428 alloc_workqueue(fmt, WQ_UNBOUND | __WQ_ORDERED | \
429 __WQ_ORDERED_EXPLICIT | (flags), 1, ##args)
431 #define create_workqueue(name) \
432 alloc_workqueue("%s", __WQ_LEGACY | WQ_MEM_RECLAIM, 1, (name))
433 #define create_freezable_workqueue(name) \
434 alloc_workqueue("%s", __WQ_LEGACY | WQ_FREEZABLE | WQ_UNBOUND | \
435 WQ_MEM_RECLAIM, 1, (name))
436 #define create_singlethread_workqueue(name) \
437 alloc_ordered_workqueue("%s", __WQ_LEGACY | WQ_MEM_RECLAIM, name)
439 extern void destroy_workqueue(struct workqueue_struct *wq);
441 struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask);
442 void free_workqueue_attrs(struct workqueue_attrs *attrs);
443 int apply_workqueue_attrs(struct workqueue_struct *wq,
444 const struct workqueue_attrs *attrs);
445 int workqueue_set_unbound_cpumask(cpumask_var_t cpumask);
447 extern bool queue_work_on(int cpu, struct workqueue_struct *wq,
448 struct work_struct *work);
449 extern bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
450 struct delayed_work *work, unsigned long delay);
451 extern bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
452 struct delayed_work *dwork, unsigned long delay);
454 extern void flush_workqueue(struct workqueue_struct *wq);
455 extern void drain_workqueue(struct workqueue_struct *wq);
457 extern int schedule_on_each_cpu(work_func_t func);
459 int execute_in_process_context(work_func_t fn, struct execute_work *);
461 extern bool flush_work(struct work_struct *work);
462 extern bool cancel_work(struct work_struct *work);
463 extern bool cancel_work_sync(struct work_struct *work);
465 extern bool flush_delayed_work(struct delayed_work *dwork);
466 extern bool cancel_delayed_work(struct delayed_work *dwork);
467 extern bool cancel_delayed_work_sync(struct delayed_work *dwork);
469 extern void workqueue_set_max_active(struct workqueue_struct *wq,
471 extern bool current_is_workqueue_rescuer(void);
472 extern bool workqueue_congested(int cpu, struct workqueue_struct *wq);
473 extern unsigned int work_busy(struct work_struct *work);
474 extern __printf(1, 2) void set_worker_desc(const char *fmt, ...);
475 extern void print_worker_info(const char *log_lvl, struct task_struct *task);
476 extern void show_workqueue_state(void);
479 * queue_work - queue work on a workqueue
480 * @wq: workqueue to use
481 * @work: work to queue
483 * Returns %false if @work was already on a queue, %true otherwise.
485 * We queue the work to the CPU on which it was submitted, but if the CPU dies
486 * it can be processed by another CPU.
488 static inline bool queue_work(struct workqueue_struct *wq,
489 struct work_struct *work)
491 return queue_work_on(WORK_CPU_UNBOUND, wq, work);
495 * queue_delayed_work - queue work on a workqueue after delay
496 * @wq: workqueue to use
497 * @dwork: delayable work to queue
498 * @delay: number of jiffies to wait before queueing
500 * Equivalent to queue_delayed_work_on() but tries to use the local CPU.
502 static inline bool queue_delayed_work(struct workqueue_struct *wq,
503 struct delayed_work *dwork,
506 return queue_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay);
510 * mod_delayed_work - modify delay of or queue a delayed work
511 * @wq: workqueue to use
512 * @dwork: work to queue
513 * @delay: number of jiffies to wait before queueing
515 * mod_delayed_work_on() on local CPU.
517 static inline bool mod_delayed_work(struct workqueue_struct *wq,
518 struct delayed_work *dwork,
521 return mod_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay);
525 * schedule_work_on - put work task on a specific cpu
526 * @cpu: cpu to put the work task on
527 * @work: job to be done
529 * This puts a job on a specific cpu
531 static inline bool schedule_work_on(int cpu, struct work_struct *work)
533 return queue_work_on(cpu, system_wq, work);
537 * schedule_work - put work task in global workqueue
538 * @work: job to be done
540 * Returns %false if @work was already on the kernel-global workqueue and
543 * This puts a job in the kernel-global workqueue if it was not already
544 * queued and leaves it in the same position on the kernel-global
545 * workqueue otherwise.
547 static inline bool schedule_work(struct work_struct *work)
549 return queue_work(system_wq, work);
553 * flush_scheduled_work - ensure that any scheduled work has run to completion.
555 * Forces execution of the kernel-global workqueue and blocks until its
558 * Think twice before calling this function! It's very easy to get into
559 * trouble if you don't take great care. Either of the following situations
560 * will lead to deadlock:
562 * One of the work items currently on the workqueue needs to acquire
563 * a lock held by your code or its caller.
565 * Your code is running in the context of a work routine.
567 * They will be detected by lockdep when they occur, but the first might not
568 * occur very often. It depends on what work items are on the workqueue and
569 * what locks they need, which you have no control over.
571 * In most situations flushing the entire workqueue is overkill; you merely
572 * need to know that a particular work item isn't queued and isn't running.
573 * In such cases you should use cancel_delayed_work_sync() or
574 * cancel_work_sync() instead.
576 static inline void flush_scheduled_work(void)
578 flush_workqueue(system_wq);
582 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
584 * @dwork: job to be done
585 * @delay: number of jiffies to wait
587 * After waiting for a given time this puts a job in the kernel-global
588 * workqueue on the specified CPU.
590 static inline bool schedule_delayed_work_on(int cpu, struct delayed_work *dwork,
593 return queue_delayed_work_on(cpu, system_wq, dwork, delay);
597 * schedule_delayed_work - put work task in global workqueue after delay
598 * @dwork: job to be done
599 * @delay: number of jiffies to wait or 0 for immediate execution
601 * After waiting for a given time this puts a job in the kernel-global
604 static inline bool schedule_delayed_work(struct delayed_work *dwork,
607 return queue_delayed_work(system_wq, dwork, delay);
611 static inline long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
615 static inline long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg)
620 long work_on_cpu(int cpu, long (*fn)(void *), void *arg);
621 long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg);
622 #endif /* CONFIG_SMP */
624 #ifdef CONFIG_FREEZER
625 extern void freeze_workqueues_begin(void);
626 extern bool freeze_workqueues_busy(void);
627 extern void thaw_workqueues(void);
628 #endif /* CONFIG_FREEZER */
631 int workqueue_sysfs_register(struct workqueue_struct *wq);
632 #else /* CONFIG_SYSFS */
633 static inline int workqueue_sysfs_register(struct workqueue_struct *wq)
635 #endif /* CONFIG_SYSFS */
637 #ifdef CONFIG_WQ_WATCHDOG
638 void wq_watchdog_touch(int cpu);
639 #else /* CONFIG_WQ_WATCHDOG */
640 static inline void wq_watchdog_touch(int cpu) { }
641 #endif /* CONFIG_WQ_WATCHDOG */
644 int workqueue_prepare_cpu(unsigned int cpu);
645 int workqueue_online_cpu(unsigned int cpu);
646 int workqueue_offline_cpu(unsigned int cpu);
649 int __init workqueue_init_early(void);
650 int __init workqueue_init(void);