/*
   * linux/kernel/workqueue.c
   *
   * Generic mechanism for defining kernel helper threads for running
   * arbitrary tasks in process context.
   *
   * Started by Ingo Molnar, Copyright (C) 2002
   *
   * Derived from the taskqueue/keventd code by:
   *
   *   David Woodhouse <dwmw2@infradead.org>

   *   Andrew Morton

   *   Kai Petzke <wpp@marie.physik.tu-berlin.de>
   *   Theodore Ts'o <tytso@mit.edu>

   *

   * Made to use alloc_percpu by Christoph Lameter.

   */
  
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/sched.h>
  #include <linux/init.h>
  #include <linux/signal.h>
  #include <linux/completion.h>
  #include <linux/workqueue.h>
  #include <linux/slab.h>
  #include <linux/cpu.h>
  #include <linux/notifier.h>
  #include <linux/kthread.h>

  #include <linux/hardirq.h>

  #include <linux/mempolicy.h>

  #include <linux/freezer.h>

  #include <linux/kallsyms.h>
  #include <linux/debug_locks.h>

  #include <linux/lockdep.h>

  #define CREATE_TRACE_POINTS
  #include <trace/events/workqueue.h>

  
  /*

   * The per-CPU workqueue (if single thread, we always use the first
   * possible cpu).

   */
  struct cpu_workqueue_struct {
  
  	spinlock_t lock;

  	struct list_head worklist;
  	wait_queue_head_t more_work;

  	struct work_struct *current_work;

  
  	struct workqueue_struct *wq;

  	struct task_struct *thread;

  } ____cacheline_aligned;
  
  /*
   * The externally visible workqueue abstraction is an array of
   * per-CPU workqueues:
   */
  struct workqueue_struct {

  	struct cpu_workqueue_struct *cpu_wq;

  	struct list_head list;

  	const char *name;

  	int singlethread;

  	int freezeable;		/* Freeze threads during suspend */

  	int rt;

  #ifdef CONFIG_LOCKDEP
  	struct lockdep_map lockdep_map;
  #endif

  };

  #ifdef CONFIG_DEBUG_OBJECTS_WORK
  
  static struct debug_obj_descr work_debug_descr;
  
  /*
   * fixup_init is called when:
   * - an active object is initialized
   */
  static int work_fixup_init(void *addr, enum debug_obj_state state)
  {
  	struct work_struct *work = addr;
  
  	switch (state) {
  	case ODEBUG_STATE_ACTIVE:
  		cancel_work_sync(work);
  		debug_object_init(work, &work_debug_descr);
  		return 1;
  	default:
  		return 0;
  	}
  }
  
  /*
   * fixup_activate is called when:
   * - an active object is activated
   * - an unknown object is activated (might be a statically initialized object)
   */
  static int work_fixup_activate(void *addr, enum debug_obj_state state)
  {
  	struct work_struct *work = addr;
  
  	switch (state) {
  
  	case ODEBUG_STATE_NOTAVAILABLE:
  		/*
  		 * This is not really a fixup. The work struct was
  		 * statically initialized. We just make sure that it
  		 * is tracked in the object tracker.
  		 */
  		if (test_bit(WORK_STRUCT_STATIC, work_data_bits(work))) {
  			debug_object_init(work, &work_debug_descr);
  			debug_object_activate(work, &work_debug_descr);
  			return 0;
  		}
  		WARN_ON_ONCE(1);
  		return 0;
  
  	case ODEBUG_STATE_ACTIVE:
  		WARN_ON(1);
  
  	default:
  		return 0;
  	}
  }
  
  /*
   * fixup_free is called when:
   * - an active object is freed
   */
  static int work_fixup_free(void *addr, enum debug_obj_state state)
  {
  	struct work_struct *work = addr;
  
  	switch (state) {
  	case ODEBUG_STATE_ACTIVE:
  		cancel_work_sync(work);
  		debug_object_free(work, &work_debug_descr);
  		return 1;
  	default:
  		return 0;
  	}
  }
  
  static struct debug_obj_descr work_debug_descr = {
  	.name		= "work_struct",
  	.fixup_init	= work_fixup_init,
  	.fixup_activate	= work_fixup_activate,
  	.fixup_free	= work_fixup_free,
  };
  
  static inline void debug_work_activate(struct work_struct *work)
  {
  	debug_object_activate(work, &work_debug_descr);
  }
  
  static inline void debug_work_deactivate(struct work_struct *work)
  {
  	debug_object_deactivate(work, &work_debug_descr);
  }
  
  void __init_work(struct work_struct *work, int onstack)
  {
  	if (onstack)
  		debug_object_init_on_stack(work, &work_debug_descr);
  	else
  		debug_object_init(work, &work_debug_descr);
  }
  EXPORT_SYMBOL_GPL(__init_work);
  
  void destroy_work_on_stack(struct work_struct *work)
  {
  	debug_object_free(work, &work_debug_descr);
  }
  EXPORT_SYMBOL_GPL(destroy_work_on_stack);
  
  #else
  static inline void debug_work_activate(struct work_struct *work) { }
  static inline void debug_work_deactivate(struct work_struct *work) { }
  #endif

  /* Serializes the accesses to the list of workqueues. */
  static DEFINE_SPINLOCK(workqueue_lock);

  static LIST_HEAD(workqueues);

  static int singlethread_cpu __read_mostly;

  static const struct cpumask *cpu_singlethread_map __read_mostly;

  /*
   * _cpu_down() first removes CPU from cpu_online_map, then CPU_DEAD
   * flushes cwq->worklist. This means that flush_workqueue/wait_on_work
   * which comes in between can't use for_each_online_cpu(). We could
   * use cpu_possible_map, the cpumask below is more a documentation
   * than optimization.
   */

  static cpumask_var_t cpu_populated_map __read_mostly;

  /* If it's single threaded, it isn't in the list of workqueues. */

  static inline int is_wq_single_threaded(struct workqueue_struct *wq)

  {

  	return wq->singlethread;

  }

  static const struct cpumask *wq_cpu_map(struct workqueue_struct *wq)

  {

  	return is_wq_single_threaded(wq)

  		? cpu_singlethread_map : cpu_populated_map;

  }

  static
  struct cpu_workqueue_struct *wq_per_cpu(struct workqueue_struct *wq, int cpu)
  {

  	if (unlikely(is_wq_single_threaded(wq)))

  		cpu = singlethread_cpu;
  	return per_cpu_ptr(wq->cpu_wq, cpu);
  }

  /*
   * Set the workqueue on which a work item is to be run
   * - Must *only* be called if the pending flag is set
   */

  static inline void set_wq_data(struct work_struct *work,
  				struct cpu_workqueue_struct *cwq)

  {

  	unsigned long new;
  
  	BUG_ON(!work_pending(work));

  	new = (unsigned long) cwq | (1UL << WORK_STRUCT_PENDING);

  	new |= WORK_STRUCT_FLAG_MASK & *work_data_bits(work);
  	atomic_long_set(&work->data, new);

  }

  static inline
  struct cpu_workqueue_struct *get_wq_data(struct work_struct *work)

  {

  	return (void *) (atomic_long_read(&work->data) & WORK_STRUCT_WQ_DATA_MASK);

  }

  static void insert_work(struct cpu_workqueue_struct *cwq,

  			struct work_struct *work, struct list_head *head)

  {

  	trace_workqueue_insertion(cwq->thread, work);

  	set_wq_data(work, cwq);

  	/*
  	 * Ensure that we get the right work->data if we see the
  	 * result of list_add() below, see try_to_grab_pending().
  	 */
  	smp_wmb();

  	list_add_tail(&work->entry, head);

  	wake_up(&cwq->more_work);
  }

  static void __queue_work(struct cpu_workqueue_struct *cwq,
  			 struct work_struct *work)
  {
  	unsigned long flags;

  	debug_work_activate(work);

  	spin_lock_irqsave(&cwq->lock, flags);

  	insert_work(cwq, work, &cwq->worklist);

  	spin_unlock_irqrestore(&cwq->lock, flags);
  }

  /**
   * queue_work - queue work on a workqueue
   * @wq: workqueue to use
   * @work: work to queue
   *

   * Returns 0 if @work was already on a queue, non-zero otherwise.

   *

   * We queue the work to the CPU on which it was submitted, but if the CPU dies
   * it can be processed by another CPU.

   */

  int queue_work(struct workqueue_struct *wq, struct work_struct *work)

  {

  	int ret;
  
  	ret = queue_work_on(get_cpu(), wq, work);
  	put_cpu();

  	return ret;
  }

  EXPORT_SYMBOL_GPL(queue_work);

  /**
   * queue_work_on - queue work on specific cpu
   * @cpu: CPU number to execute work on
   * @wq: workqueue to use
   * @work: work to queue
   *
   * Returns 0 if @work was already on a queue, non-zero otherwise.
   *
   * We queue the work to a specific CPU, the caller must ensure it
   * can't go away.
   */
  int
  queue_work_on(int cpu, struct workqueue_struct *wq, struct work_struct *work)
  {
  	int ret = 0;
  
  	if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {
  		BUG_ON(!list_empty(&work->entry));
  		__queue_work(wq_per_cpu(wq, cpu), work);
  		ret = 1;
  	}
  	return ret;
  }
  EXPORT_SYMBOL_GPL(queue_work_on);

  static void delayed_work_timer_fn(unsigned long __data)

  {

  	struct delayed_work *dwork = (struct delayed_work *)__data;

  	struct cpu_workqueue_struct *cwq = get_wq_data(&dwork->work);
  	struct workqueue_struct *wq = cwq->wq;

  	__queue_work(wq_per_cpu(wq, smp_processor_id()), &dwork->work);

  }

  /**
   * queue_delayed_work - queue work on a workqueue after delay
   * @wq: workqueue to use

   * @dwork: delayable work to queue

   * @delay: number of jiffies to wait before queueing
   *

   * Returns 0 if @work was already on a queue, non-zero otherwise.

   */

  int queue_delayed_work(struct workqueue_struct *wq,

  			struct delayed_work *dwork, unsigned long delay)

  {

  	if (delay == 0)

  		return queue_work(wq, &dwork->work);

  	return queue_delayed_work_on(-1, wq, dwork, delay);

  }

  EXPORT_SYMBOL_GPL(queue_delayed_work);

  /**
   * queue_delayed_work_on - queue work on specific CPU after delay
   * @cpu: CPU number to execute work on
   * @wq: workqueue to use

   * @dwork: work to queue

   * @delay: number of jiffies to wait before queueing
   *

   * Returns 0 if @work was already on a queue, non-zero otherwise.

   */

  int queue_delayed_work_on(int cpu, struct workqueue_struct *wq,

  			struct delayed_work *dwork, unsigned long delay)

  {
  	int ret = 0;

  	struct timer_list *timer = &dwork->timer;
  	struct work_struct *work = &dwork->work;

  	if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work))) {

  		BUG_ON(timer_pending(timer));
  		BUG_ON(!list_empty(&work->entry));

  		timer_stats_timer_set_start_info(&dwork->timer);

  		/* This stores cwq for the moment, for the timer_fn */

  		set_wq_data(work, wq_per_cpu(wq, raw_smp_processor_id()));

  		timer->expires = jiffies + delay;

  		timer->data = (unsigned long)dwork;

  		timer->function = delayed_work_timer_fn;

  
  		if (unlikely(cpu >= 0))
  			add_timer_on(timer, cpu);
  		else
  			add_timer(timer);

  		ret = 1;
  	}
  	return ret;
  }

  EXPORT_SYMBOL_GPL(queue_delayed_work_on);

  static void run_workqueue(struct cpu_workqueue_struct *cwq)

  {

  	spin_lock_irq(&cwq->lock);

  	while (!list_empty(&cwq->worklist)) {
  		struct work_struct *work = list_entry(cwq->worklist.next,
  						struct work_struct, entry);

  		work_func_t f = work->func;

  #ifdef CONFIG_LOCKDEP
  		/*
  		 * It is permissible to free the struct work_struct
  		 * from inside the function that is called from it,
  		 * this we need to take into account for lockdep too.
  		 * To avoid bogus "held lock freed" warnings as well
  		 * as problems when looking into work->lockdep_map,
  		 * make a copy and use that here.
  		 */
  		struct lockdep_map lockdep_map = work->lockdep_map;
  #endif

  		trace_workqueue_execution(cwq->thread, work);

  		debug_work_deactivate(work);

  		cwq->current_work = work;

  		list_del_init(cwq->worklist.next);

  		spin_unlock_irq(&cwq->lock);

  		BUG_ON(get_wq_data(work) != cwq);

  		work_clear_pending(work);

  		lock_map_acquire(&cwq->wq->lockdep_map);
  		lock_map_acquire(&lockdep_map);

  		f(work);

  		lock_map_release(&lockdep_map);
  		lock_map_release(&cwq->wq->lockdep_map);

  		if (unlikely(in_atomic() || lockdep_depth(current) > 0)) {
  			printk(KERN_ERR "BUG: workqueue leaked lock or atomic: "
  					"%s/0x%08x/%d
  ",
  					current->comm, preempt_count(),

  				       	task_pid_nr(current));

  			printk(KERN_ERR "    last function: ");
  			print_symbol("%s
  ", (unsigned long)f);
  			debug_show_held_locks(current);
  			dump_stack();
  		}

  		spin_lock_irq(&cwq->lock);

  		cwq->current_work = NULL;

  	}

  	spin_unlock_irq(&cwq->lock);

  }
  
  static int worker_thread(void *__cwq)
  {
  	struct cpu_workqueue_struct *cwq = __cwq;

  	DEFINE_WAIT(wait);

  	if (cwq->wq->freezeable)
  		set_freezable();

  	for (;;) {

  		prepare_to_wait(&cwq->more_work, &wait, TASK_INTERRUPTIBLE);

  		if (!freezing(current) &&
  		    !kthread_should_stop() &&
  		    list_empty(&cwq->worklist))

  			schedule();

  		finish_wait(&cwq->more_work, &wait);

  		try_to_freeze();

  		if (kthread_should_stop())

  			break;

  		run_workqueue(cwq);

  	}

  	return 0;
  }

  struct wq_barrier {
  	struct work_struct	work;
  	struct completion	done;
  };
  
  static void wq_barrier_func(struct work_struct *work)
  {
  	struct wq_barrier *barr = container_of(work, struct wq_barrier, work);
  	complete(&barr->done);
  }

  static void insert_wq_barrier(struct cpu_workqueue_struct *cwq,

  			struct wq_barrier *barr, struct list_head *head)

  {

  	/*
  	 * debugobject calls are safe here even with cwq->lock locked
  	 * as we know for sure that this will not trigger any of the
  	 * checks and call back into the fixup functions where we
  	 * might deadlock.
  	 */
  	INIT_WORK_ON_STACK(&barr->work, wq_barrier_func);

  	__set_bit(WORK_STRUCT_PENDING, work_data_bits(&barr->work));
  
  	init_completion(&barr->done);

  	debug_work_activate(&barr->work);

  	insert_work(cwq, &barr->work, head);

  }

  static int flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)

  {

  	int active = 0;
  	struct wq_barrier barr;

  	WARN_ON(cwq->thread == current);

  	spin_lock_irq(&cwq->lock);
  	if (!list_empty(&cwq->worklist) || cwq->current_work != NULL) {
  		insert_wq_barrier(cwq, &barr, &cwq->worklist);
  		active = 1;

  	}

  	spin_unlock_irq(&cwq->lock);

  	if (active) {

  		wait_for_completion(&barr.done);

  		destroy_work_on_stack(&barr.work);
  	}

  
  	return active;

  }

  /**

   * flush_workqueue - ensure that any scheduled work has run to completion.

   * @wq: workqueue to flush

   *
   * Forces execution of the workqueue and blocks until its completion.
   * This is typically used in driver shutdown handlers.
   *

   * We sleep until all works which were queued on entry have been handled,
   * but we are not livelocked by new incoming ones.

   *
   * This function used to run the workqueues itself.  Now we just wait for the
   * helper threads to do it.
   */

  void flush_workqueue(struct workqueue_struct *wq)

  {

  	const struct cpumask *cpu_map = wq_cpu_map(wq);

  	int cpu;

  	might_sleep();

  	lock_map_acquire(&wq->lockdep_map);
  	lock_map_release(&wq->lockdep_map);

  	for_each_cpu(cpu, cpu_map)

  		flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, cpu));

  }

  EXPORT_SYMBOL_GPL(flush_workqueue);

  /**
   * flush_work - block until a work_struct's callback has terminated
   * @work: the work which is to be flushed
   *

   * Returns false if @work has already terminated.
   *

   * It is expected that, prior to calling flush_work(), the caller has
   * arranged for the work to not be requeued, otherwise it doesn't make
   * sense to use this function.
   */
  int flush_work(struct work_struct *work)
  {
  	struct cpu_workqueue_struct *cwq;
  	struct list_head *prev;
  	struct wq_barrier barr;
  
  	might_sleep();
  	cwq = get_wq_data(work);
  	if (!cwq)
  		return 0;

  	lock_map_acquire(&cwq->wq->lockdep_map);
  	lock_map_release(&cwq->wq->lockdep_map);

  	prev = NULL;
  	spin_lock_irq(&cwq->lock);
  	if (!list_empty(&work->entry)) {
  		/*
  		 * See the comment near try_to_grab_pending()->smp_rmb().
  		 * If it was re-queued under us we are not going to wait.
  		 */
  		smp_rmb();
  		if (unlikely(cwq != get_wq_data(work)))
  			goto out;
  		prev = &work->entry;
  	} else {
  		if (cwq->current_work != work)
  			goto out;
  		prev = &cwq->worklist;
  	}
  	insert_wq_barrier(cwq, &barr, prev->next);
  out:
  	spin_unlock_irq(&cwq->lock);
  	if (!prev)
  		return 0;
  
  	wait_for_completion(&barr.done);

  	destroy_work_on_stack(&barr.work);

  	return 1;
  }
  EXPORT_SYMBOL_GPL(flush_work);

  /*

   * Upon a successful return (>= 0), the caller "owns" WORK_STRUCT_PENDING bit,

   * so this work can't be re-armed in any way.
   */
  static int try_to_grab_pending(struct work_struct *work)
  {
  	struct cpu_workqueue_struct *cwq;

  	int ret = -1;

  
  	if (!test_and_set_bit(WORK_STRUCT_PENDING, work_data_bits(work)))

  		return 0;

  
  	/*
  	 * The queueing is in progress, or it is already queued. Try to
  	 * steal it from ->worklist without clearing WORK_STRUCT_PENDING.
  	 */
  
  	cwq = get_wq_data(work);
  	if (!cwq)
  		return ret;
  
  	spin_lock_irq(&cwq->lock);
  	if (!list_empty(&work->entry)) {
  		/*
  		 * This work is queued, but perhaps we locked the wrong cwq.
  		 * In that case we must see the new value after rmb(), see
  		 * insert_work()->wmb().
  		 */
  		smp_rmb();
  		if (cwq == get_wq_data(work)) {

  			debug_work_deactivate(work);

  			list_del_init(&work->entry);
  			ret = 1;
  		}
  	}
  	spin_unlock_irq(&cwq->lock);
  
  	return ret;
  }
  
  static void wait_on_cpu_work(struct cpu_workqueue_struct *cwq,

  				struct work_struct *work)
  {
  	struct wq_barrier barr;
  	int running = 0;
  
  	spin_lock_irq(&cwq->lock);
  	if (unlikely(cwq->current_work == work)) {

  		insert_wq_barrier(cwq, &barr, cwq->worklist.next);

  		running = 1;
  	}
  	spin_unlock_irq(&cwq->lock);

  	if (unlikely(running)) {

  		wait_for_completion(&barr.done);

  		destroy_work_on_stack(&barr.work);
  	}

  }

  static void wait_on_work(struct work_struct *work)

  {
  	struct cpu_workqueue_struct *cwq;

  	struct workqueue_struct *wq;

  	const struct cpumask *cpu_map;

  	int cpu;

  	might_sleep();

  	lock_map_acquire(&work->lockdep_map);
  	lock_map_release(&work->lockdep_map);

  	cwq = get_wq_data(work);

  	if (!cwq)

  		return;

  	wq = cwq->wq;
  	cpu_map = wq_cpu_map(wq);

  	for_each_cpu(cpu, cpu_map)

  		wait_on_cpu_work(per_cpu_ptr(wq->cpu_wq, cpu), work);
  }

  static int __cancel_work_timer(struct work_struct *work,
  				struct timer_list* timer)
  {
  	int ret;
  
  	do {
  		ret = (timer && likely(del_timer(timer)));
  		if (!ret)
  			ret = try_to_grab_pending(work);
  		wait_on_work(work);
  	} while (unlikely(ret < 0));
  
  	work_clear_pending(work);
  	return ret;
  }

  /**
   * cancel_work_sync - block until a work_struct's callback has terminated
   * @work: the work which is to be flushed
   *

   * Returns true if @work was pending.
   *

   * cancel_work_sync() will cancel the work if it is queued. If the work's
   * callback appears to be running, cancel_work_sync() will block until it
   * has completed.
   *
   * It is possible to use this function if the work re-queues itself. It can
   * cancel the work even if it migrates to another workqueue, however in that
   * case it only guarantees that work->func() has completed on the last queued
   * workqueue.
   *
   * cancel_work_sync(&delayed_work->work) should be used only if ->timer is not
   * pending, otherwise it goes into a busy-wait loop until the timer expires.
   *
   * The caller must ensure that workqueue_struct on which this work was last
   * queued can't be destroyed before this function returns.
   */

  int cancel_work_sync(struct work_struct *work)

  {

  	return __cancel_work_timer(work, NULL);

  }

  EXPORT_SYMBOL_GPL(cancel_work_sync);

  /**

   * cancel_delayed_work_sync - reliably kill off a delayed work.

   * @dwork: the delayed work struct
   *

   * Returns true if @dwork was pending.
   *

   * It is possible to use this function if @dwork rearms itself via queue_work()
   * or queue_delayed_work(). See also the comment for cancel_work_sync().
   */

  int cancel_delayed_work_sync(struct delayed_work *dwork)

  {

  	return __cancel_work_timer(&dwork->work, &dwork->timer);

  }

  EXPORT_SYMBOL(cancel_delayed_work_sync);

  static struct workqueue_struct *keventd_wq __read_mostly;

  /**
   * schedule_work - put work task in global workqueue
   * @work: job to be done
   *

   * Returns zero if @work was already on the kernel-global workqueue and
   * non-zero otherwise.
   *
   * This puts a job in the kernel-global workqueue if it was not already
   * queued and leaves it in the same position on the kernel-global
   * workqueue otherwise.

   */

  int schedule_work(struct work_struct *work)

  {
  	return queue_work(keventd_wq, work);
  }

  EXPORT_SYMBOL(schedule_work);

  /*
   * schedule_work_on - put work task on a specific cpu
   * @cpu: cpu to put the work task on
   * @work: job to be done
   *
   * This puts a job on a specific cpu
   */
  int schedule_work_on(int cpu, struct work_struct *work)
  {
  	return queue_work_on(cpu, keventd_wq, work);
  }
  EXPORT_SYMBOL(schedule_work_on);

  /**
   * schedule_delayed_work - put work task in global workqueue after delay

   * @dwork: job to be done
   * @delay: number of jiffies to wait or 0 for immediate execution

   *
   * After waiting for a given time this puts a job in the kernel-global
   * workqueue.
   */

  int schedule_delayed_work(struct delayed_work *dwork,

  					unsigned long delay)

  {

  	return queue_delayed_work(keventd_wq, dwork, delay);

  }

  EXPORT_SYMBOL(schedule_delayed_work);

  /**

   * flush_delayed_work - block until a dwork_struct's callback has terminated
   * @dwork: the delayed work which is to be flushed
   *
   * Any timeout is cancelled, and any pending work is run immediately.
   */
  void flush_delayed_work(struct delayed_work *dwork)
  {
  	if (del_timer_sync(&dwork->timer)) {
  		struct cpu_workqueue_struct *cwq;
  		cwq = wq_per_cpu(keventd_wq, get_cpu());
  		__queue_work(cwq, &dwork->work);
  		put_cpu();
  	}
  	flush_work(&dwork->work);
  }
  EXPORT_SYMBOL(flush_delayed_work);
  
  /**

   * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
   * @cpu: cpu to use

   * @dwork: job to be done

   * @delay: number of jiffies to wait
   *
   * After waiting for a given time this puts a job in the kernel-global
   * workqueue on the specified CPU.
   */

  int schedule_delayed_work_on(int cpu,

  			struct delayed_work *dwork, unsigned long delay)

  {

  	return queue_delayed_work_on(cpu, keventd_wq, dwork, delay);

  }

  EXPORT_SYMBOL(schedule_delayed_work_on);

  /**
   * schedule_on_each_cpu - call a function on each online CPU from keventd
   * @func: the function to call

   *
   * Returns zero on success.
   * Returns -ve errno on failure.
   *

   * schedule_on_each_cpu() is very slow.
   */

  int schedule_on_each_cpu(work_func_t func)

  {
  	int cpu;

  	int orig = -1;

  	struct work_struct *works;

  	works = alloc_percpu(struct work_struct);
  	if (!works)

  		return -ENOMEM;

  	get_online_cpus();

  	/*

  	 * When running in keventd don't schedule a work item on
  	 * itself.  Can just call directly because the work queue is
  	 * already bound.  This also is faster.

  	 */

  	if (current_is_keventd())

  		orig = raw_smp_processor_id();

  	for_each_online_cpu(cpu) {

  		struct work_struct *work = per_cpu_ptr(works, cpu);
  
  		INIT_WORK(work, func);

  		if (cpu != orig)

  			schedule_work_on(cpu, work);

  	}

  	if (orig >= 0)
  		func(per_cpu_ptr(works, orig));
  
  	for_each_online_cpu(cpu)
  		flush_work(per_cpu_ptr(works, cpu));

  	put_online_cpus();

  	free_percpu(works);

  	return 0;
  }

  void flush_scheduled_work(void)
  {
  	flush_workqueue(keventd_wq);
  }

  EXPORT_SYMBOL(flush_scheduled_work);

  
  /**

   * execute_in_process_context - reliably execute the routine with user context
   * @fn:		the function to execute

   * @ew:		guaranteed storage for the execute work structure (must
   *		be available when the work executes)
   *
   * Executes the function immediately if process context is available,
   * otherwise schedules the function for delayed execution.
   *
   * Returns:	0 - function was executed
   *		1 - function was scheduled for execution
   */

  int execute_in_process_context(work_func_t fn, struct execute_work *ew)

  {
  	if (!in_interrupt()) {

  		fn(&ew->work);

  		return 0;
  	}

  	INIT_WORK(&ew->work, fn);

  	schedule_work(&ew->work);
  
  	return 1;
  }
  EXPORT_SYMBOL_GPL(execute_in_process_context);

  int keventd_up(void)
  {
  	return keventd_wq != NULL;
  }
  
  int current_is_keventd(void)
  {
  	struct cpu_workqueue_struct *cwq;

  	int cpu = raw_smp_processor_id(); /* preempt-safe: keventd is per-cpu */

  	int ret = 0;
  
  	BUG_ON(!keventd_wq);

  	cwq = per_cpu_ptr(keventd_wq->cpu_wq, cpu);

  	if (current == cwq->thread)
  		ret = 1;
  
  	return ret;
  
  }

  static struct cpu_workqueue_struct *
  init_cpu_workqueue(struct workqueue_struct *wq, int cpu)

  {

  	struct cpu_workqueue_struct *cwq = per_cpu_ptr(wq->cpu_wq, cpu);

  	cwq->wq = wq;
  	spin_lock_init(&cwq->lock);
  	INIT_LIST_HEAD(&cwq->worklist);
  	init_waitqueue_head(&cwq->more_work);
  
  	return cwq;

  }

  static int create_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
  {

  	struct sched_param param = { .sched_priority = MAX_RT_PRIO-1 };

  	struct workqueue_struct *wq = cwq->wq;

  	const char *fmt = is_wq_single_threaded(wq) ? "%s" : "%s/%d";

  	struct task_struct *p;
  
  	p = kthread_create(worker_thread, cwq, fmt, wq->name, cpu);
  	/*
  	 * Nobody can add the work_struct to this cwq,
  	 *	if (caller is __create_workqueue)
  	 *		nobody should see this wq
  	 *	else // caller is CPU_UP_PREPARE
  	 *		cpu is not on cpu_online_map
  	 * so we can abort safely.
  	 */
  	if (IS_ERR(p))
  		return PTR_ERR(p);

  	if (cwq->wq->rt)
  		sched_setscheduler_nocheck(p, SCHED_FIFO, &param);

  	cwq->thread = p;

  	trace_workqueue_creation(cwq->thread, cpu);

  	return 0;
  }

  static void start_workqueue_thread(struct cpu_workqueue_struct *cwq, int cpu)
  {
  	struct task_struct *p = cwq->thread;
  
  	if (p != NULL) {
  		if (cpu >= 0)
  			kthread_bind(p, cpu);
  		wake_up_process(p);
  	}
  }

  struct workqueue_struct *__create_workqueue_key(const char *name,
  						int singlethread,
  						int freezeable,

  						int rt,

  						struct lock_class_key *key,
  						const char *lock_name)

  {

  	struct workqueue_struct *wq;

  	struct cpu_workqueue_struct *cwq;
  	int err = 0, cpu;

  	wq = kzalloc(sizeof(*wq), GFP_KERNEL);
  	if (!wq)
  		return NULL;
  
  	wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);
  	if (!wq->cpu_wq) {
  		kfree(wq);
  		return NULL;
  	}
  
  	wq->name = name;

  	lockdep_init_map(&wq->lockdep_map, lock_name, key, 0);

  	wq->singlethread = singlethread;

  	wq->freezeable = freezeable;

  	wq->rt = rt;

  	INIT_LIST_HEAD(&wq->list);

  
  	if (singlethread) {

  		cwq = init_cpu_workqueue(wq, singlethread_cpu);
  		err = create_workqueue_thread(cwq, singlethread_cpu);

  		start_workqueue_thread(cwq, -1);

  	} else {

  		cpu_maps_update_begin();

  		/*
  		 * We must place this wq on list even if the code below fails.
  		 * cpu_down(cpu) can remove cpu from cpu_populated_map before
  		 * destroy_workqueue() takes the lock, in that case we leak
  		 * cwq[cpu]->thread.
  		 */

  		spin_lock(&workqueue_lock);

  		list_add(&wq->list, &workqueues);

  		spin_unlock(&workqueue_lock);

  		/*
  		 * We must initialize cwqs for each possible cpu even if we
  		 * are going to call destroy_workqueue() finally. Otherwise
  		 * cpu_up() can hit the uninitialized cwq once we drop the
  		 * lock.
  		 */

  		for_each_possible_cpu(cpu) {
  			cwq = init_cpu_workqueue(wq, cpu);
  			if (err || !cpu_online(cpu))
  				continue;
  			err = create_workqueue_thread(cwq, cpu);

  			start_workqueue_thread(cwq, cpu);

  		}

  		cpu_maps_update_done();

  	}
  
  	if (err) {
  		destroy_workqueue(wq);
  		wq = NULL;
  	}
  	return wq;
  }

  EXPORT_SYMBOL_GPL(__create_workqueue_key);

  static void cleanup_workqueue_thread(struct cpu_workqueue_struct *cwq)

  {

  	/*

  	 * Our caller is either destroy_workqueue() or CPU_POST_DEAD,
  	 * cpu_add_remove_lock protects cwq->thread.

  	 */
  	if (cwq->thread == NULL)
  		return;

  	lock_map_acquire(&cwq->wq->lockdep_map);
  	lock_map_release(&cwq->wq->lockdep_map);

  	flush_cpu_workqueue(cwq);

  	/*

  	 * If the caller is CPU_POST_DEAD and cwq->worklist was not empty,

  	 * a concurrent flush_workqueue() can insert a barrier after us.
  	 * However, in that case run_workqueue() won't return and check
  	 * kthread_should_stop() until it flushes all work_struct's.

  	 * When ->worklist becomes empty it is safe to exit because no
  	 * more work_structs can be queued on this cwq: flush_workqueue
  	 * checks list_empty(), and a "normal" queue_work() can't use
  	 * a dead CPU.
  	 */

  	trace_workqueue_destruction(cwq->thread);

  	kthread_stop(cwq->thread);
  	cwq->thread = NULL;

  }
  
  /**
   * destroy_workqueue - safely terminate a workqueue
   * @wq: target workqueue
   *
   * Safely destroy a workqueue. All work currently pending will be done first.
   */
  void destroy_workqueue(struct workqueue_struct *wq)
  {

  	const struct cpumask *cpu_map = wq_cpu_map(wq);

  	int cpu;

  	cpu_maps_update_begin();

  	spin_lock(&workqueue_lock);

  	list_del(&wq->list);

  	spin_unlock(&workqueue_lock);

  	for_each_cpu(cpu, cpu_map)

  		cleanup_workqueue_thread(per_cpu_ptr(wq->cpu_wq, cpu));

   	cpu_maps_update_done();

  	free_percpu(wq->cpu_wq);
  	kfree(wq);
  }
  EXPORT_SYMBOL_GPL(destroy_workqueue);
  
  static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
  						unsigned long action,
  						void *hcpu)
  {
  	unsigned int cpu = (unsigned long)hcpu;
  	struct cpu_workqueue_struct *cwq;
  	struct workqueue_struct *wq;

  	int ret = NOTIFY_OK;

  	action &= ~CPU_TASKS_FROZEN;

  	switch (action) {

  	case CPU_UP_PREPARE:

  		cpumask_set_cpu(cpu, cpu_populated_map);

  	}

  undo:

  	list_for_each_entry(wq, &workqueues, list) {
  		cwq = per_cpu_ptr(wq->cpu_wq, cpu);
  
  		switch (action) {
  		case CPU_UP_PREPARE:
  			if (!create_workqueue_thread(cwq, cpu))
  				break;

  			printk(KERN_ERR "workqueue [%s] for %i failed
  ",
  				wq->name, cpu);

  			action = CPU_UP_CANCELED;
  			ret = NOTIFY_BAD;
  			goto undo;

  
  		case CPU_ONLINE:

  			start_workqueue_thread(cwq, cpu);

  			break;
  
  		case CPU_UP_CANCELED:

  			start_workqueue_thread(cwq, -1);

  		case CPU_POST_DEAD:

  			cleanup_workqueue_thread(cwq);

  			break;
  		}

  	}

  	switch (action) {
  	case CPU_UP_CANCELED:

  	case CPU_POST_DEAD:

  		cpumask_clear_cpu(cpu, cpu_populated_map);

  	}

  	return ret;

  }

  #ifdef CONFIG_SMP

  struct work_for_cpu {

  	struct completion completion;

  	long (*fn)(void *);
  	void *arg;
  	long ret;
  };

  static int do_work_for_cpu(void *_wfc)

  {

  	struct work_for_cpu *wfc = _wfc;

  	wfc->ret = wfc->fn(wfc->arg);

  	complete(&wfc->completion);
  	return 0;

  }
  
  /**
   * work_on_cpu - run a function in user context on a particular cpu
   * @cpu: the cpu to run on
   * @fn: the function to run
   * @arg: the function arg
   *

   * This will return the value @fn returns.
   * It is up to the caller to ensure that the cpu doesn't go offline.

   * The caller must not hold any locks which would prevent @fn from completing.

   */
  long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)
  {

  	struct task_struct *sub_thread;
  	struct work_for_cpu wfc = {
  		.completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),
  		.fn = fn,
  		.arg = arg,
  	};
  
  	sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");
  	if (IS_ERR(sub_thread))
  		return PTR_ERR(sub_thread);
  	kthread_bind(sub_thread, cpu);
  	wake_up_process(sub_thread);
  	wait_for_completion(&wfc.completion);

  	return wfc.ret;
  }
  EXPORT_SYMBOL_GPL(work_on_cpu);
  #endif /* CONFIG_SMP */

  void __init init_workqueues(void)

  {

  	alloc_cpumask_var(&cpu_populated_map, GFP_KERNEL);
  
  	cpumask_copy(cpu_populated_map, cpu_online_mask);
  	singlethread_cpu = cpumask_first(cpu_possible_mask);
  	cpu_singlethread_map = cpumask_of(singlethread_cpu);

  	hotcpu_notifier(workqueue_cpu_callback, 0);
  	keventd_wq = create_workqueue("events");
  	BUG_ON(!keventd_wq);
  }