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

   *
   * Made to use alloc_percpu by Christoph Lameter <clameter@sgi.com>.

   */
  
  #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>
  
  /*
   * The per-CPU workqueue (if single thread, we always use cpu 0's).
   *
   * The sequence counters are for flush_scheduled_work().  It wants to wait
   * until until all currently-scheduled works are completed, but it doesn't
   * want to be livelocked by new, incoming ones.  So it waits until
   * remove_sequence is >= the insert_sequence which pertained when
   * flush_scheduled_work() was called.
   */
  struct cpu_workqueue_struct {
  
  	spinlock_t lock;
  
  	long remove_sequence;	/* Least-recently added (next to run) */
  	long insert_sequence;	/* Next to add */
  
  	struct list_head worklist;
  	wait_queue_head_t more_work;
  	wait_queue_head_t work_done;
  
  	struct workqueue_struct *wq;
  	task_t *thread;
  
  	int run_depth;		/* Detect run_workqueue() recursion depth */
  } ____cacheline_aligned;
  
  /*
   * The externally visible workqueue abstraction is an array of
   * per-CPU workqueues:
   */
  struct workqueue_struct {

  	struct cpu_workqueue_struct *cpu_wq;

  	const char *name;
  	struct list_head list; 	/* Empty if single thread */
  };
  
  /* All the per-cpu workqueues on the system, for hotplug cpu to add/remove
     threads to each one as cpus come/go. */
  static DEFINE_SPINLOCK(workqueue_lock);
  static LIST_HEAD(workqueues);
  
  /* If it's single threaded, it isn't in the list of workqueues. */
  static inline int is_single_threaded(struct workqueue_struct *wq)
  {
  	return list_empty(&wq->list);
  }
  
  /* Preempt must be disabled. */
  static void __queue_work(struct cpu_workqueue_struct *cwq,
  			 struct work_struct *work)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&cwq->lock, flags);
  	work->wq_data = cwq;
  	list_add_tail(&work->entry, &cwq->worklist);
  	cwq->insert_sequence++;
  	wake_up(&cwq->more_work);
  	spin_unlock_irqrestore(&cwq->lock, flags);
  }
  
  /*
   * Queue work on a workqueue. Return non-zero if it was successfully
   * added.
   *
   * We queue the work to the CPU it was submitted, but there is no
   * guarantee that it will be processed by that CPU.
   */
  int fastcall queue_work(struct workqueue_struct *wq, struct work_struct *work)
  {
  	int ret = 0, cpu = get_cpu();
  
  	if (!test_and_set_bit(0, &work->pending)) {
  		if (unlikely(is_single_threaded(wq)))
  			cpu = 0;
  		BUG_ON(!list_empty(&work->entry));

  		__queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);

  		ret = 1;
  	}
  	put_cpu();
  	return ret;
  }
  
  static void delayed_work_timer_fn(unsigned long __data)
  {
  	struct work_struct *work = (struct work_struct *)__data;
  	struct workqueue_struct *wq = work->wq_data;
  	int cpu = smp_processor_id();
  
  	if (unlikely(is_single_threaded(wq)))
  		cpu = 0;

  	__queue_work(per_cpu_ptr(wq->cpu_wq, cpu), work);

  }
  
  int fastcall queue_delayed_work(struct workqueue_struct *wq,
  			struct work_struct *work, unsigned long delay)
  {
  	int ret = 0;
  	struct timer_list *timer = &work->timer;
  
  	if (!test_and_set_bit(0, &work->pending)) {
  		BUG_ON(timer_pending(timer));
  		BUG_ON(!list_empty(&work->entry));
  
  		/* This stores wq for the moment, for the timer_fn */
  		work->wq_data = wq;
  		timer->expires = jiffies + delay;
  		timer->data = (unsigned long)work;
  		timer->function = delayed_work_timer_fn;
  		add_timer(timer);
  		ret = 1;
  	}
  	return ret;
  }
  
  static inline void run_workqueue(struct cpu_workqueue_struct *cwq)
  {
  	unsigned long flags;
  
  	/*
  	 * Keep taking off work from the queue until
  	 * done.
  	 */
  	spin_lock_irqsave(&cwq->lock, flags);
  	cwq->run_depth++;
  	if (cwq->run_depth > 3) {
  		/* morton gets to eat his hat */
  		printk("%s: recursion depth exceeded: %d
  ",
  			__FUNCTION__, cwq->run_depth);
  		dump_stack();
  	}
  	while (!list_empty(&cwq->worklist)) {
  		struct work_struct *work = list_entry(cwq->worklist.next,
  						struct work_struct, entry);
  		void (*f) (void *) = work->func;
  		void *data = work->data;
  
  		list_del_init(cwq->worklist.next);
  		spin_unlock_irqrestore(&cwq->lock, flags);
  
  		BUG_ON(work->wq_data != cwq);
  		clear_bit(0, &work->pending);
  		f(data);
  
  		spin_lock_irqsave(&cwq->lock, flags);
  		cwq->remove_sequence++;
  		wake_up(&cwq->work_done);
  	}
  	cwq->run_depth--;
  	spin_unlock_irqrestore(&cwq->lock, flags);
  }
  
  static int worker_thread(void *__cwq)
  {
  	struct cpu_workqueue_struct *cwq = __cwq;
  	DECLARE_WAITQUEUE(wait, current);
  	struct k_sigaction sa;
  	sigset_t blocked;
  
  	current->flags |= PF_NOFREEZE;
  
  	set_user_nice(current, -5);
  
  	/* Block and flush all signals */
  	sigfillset(&blocked);
  	sigprocmask(SIG_BLOCK, &blocked, NULL);
  	flush_signals(current);
  
  	/* SIG_IGN makes children autoreap: see do_notify_parent(). */
  	sa.sa.sa_handler = SIG_IGN;
  	sa.sa.sa_flags = 0;
  	siginitset(&sa.sa.sa_mask, sigmask(SIGCHLD));
  	do_sigaction(SIGCHLD, &sa, (struct k_sigaction *)0);
  
  	set_current_state(TASK_INTERRUPTIBLE);
  	while (!kthread_should_stop()) {
  		add_wait_queue(&cwq->more_work, &wait);
  		if (list_empty(&cwq->worklist))
  			schedule();
  		else
  			__set_current_state(TASK_RUNNING);
  		remove_wait_queue(&cwq->more_work, &wait);
  
  		if (!list_empty(&cwq->worklist))
  			run_workqueue(cwq);
  		set_current_state(TASK_INTERRUPTIBLE);
  	}
  	__set_current_state(TASK_RUNNING);
  	return 0;
  }
  
  static void flush_cpu_workqueue(struct cpu_workqueue_struct *cwq)
  {
  	if (cwq->thread == current) {
  		/*
  		 * Probably keventd trying to flush its own queue. So simply run
  		 * it by hand rather than deadlocking.
  		 */
  		run_workqueue(cwq);
  	} else {
  		DEFINE_WAIT(wait);
  		long sequence_needed;
  
  		spin_lock_irq(&cwq->lock);
  		sequence_needed = cwq->insert_sequence;
  
  		while (sequence_needed - cwq->remove_sequence > 0) {
  			prepare_to_wait(&cwq->work_done, &wait,
  					TASK_UNINTERRUPTIBLE);
  			spin_unlock_irq(&cwq->lock);
  			schedule();
  			spin_lock_irq(&cwq->lock);
  		}
  		finish_wait(&cwq->work_done, &wait);
  		spin_unlock_irq(&cwq->lock);
  	}
  }
  
  /*
   * flush_workqueue - ensure that any scheduled work has run to completion.
   *
   * Forces execution of the workqueue and blocks until its completion.
   * This is typically used in driver shutdown handlers.
   *
   * This function will sample each workqueue's current insert_sequence number and
   * will sleep until the head sequence is greater than or equal to that.  This
   * means that 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 fastcall flush_workqueue(struct workqueue_struct *wq)
  {
  	might_sleep();
  
  	if (is_single_threaded(wq)) {
  		/* Always use cpu 0's area. */

  		flush_cpu_workqueue(per_cpu_ptr(wq->cpu_wq, 0));

  	} else {
  		int cpu;
  
  		lock_cpu_hotplug();
  		for_each_online_cpu(cpu)

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

  		unlock_cpu_hotplug();
  	}
  }
  
  static struct task_struct *create_workqueue_thread(struct workqueue_struct *wq,
  						   int cpu)
  {

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

  	struct task_struct *p;
  
  	spin_lock_init(&cwq->lock);
  	cwq->wq = wq;
  	cwq->thread = NULL;
  	cwq->insert_sequence = 0;
  	cwq->remove_sequence = 0;
  	INIT_LIST_HEAD(&cwq->worklist);
  	init_waitqueue_head(&cwq->more_work);
  	init_waitqueue_head(&cwq->work_done);
  
  	if (is_single_threaded(wq))
  		p = kthread_create(worker_thread, cwq, "%s", wq->name);
  	else
  		p = kthread_create(worker_thread, cwq, "%s/%d", wq->name, cpu);
  	if (IS_ERR(p))
  		return NULL;
  	cwq->thread = p;
  	return p;
  }
  
  struct workqueue_struct *__create_workqueue(const char *name,
  					    int singlethread)
  {
  	int cpu, destroy = 0;
  	struct workqueue_struct *wq;
  	struct task_struct *p;

  	wq = kzalloc(sizeof(*wq), GFP_KERNEL);

  	if (!wq)
  		return NULL;

  	wq->cpu_wq = alloc_percpu(struct cpu_workqueue_struct);

  	wq->name = name;
  	/* We don't need the distraction of CPUs appearing and vanishing. */
  	lock_cpu_hotplug();
  	if (singlethread) {
  		INIT_LIST_HEAD(&wq->list);
  		p = create_workqueue_thread(wq, 0);
  		if (!p)
  			destroy = 1;
  		else
  			wake_up_process(p);
  	} else {
  		spin_lock(&workqueue_lock);
  		list_add(&wq->list, &workqueues);
  		spin_unlock(&workqueue_lock);
  		for_each_online_cpu(cpu) {
  			p = create_workqueue_thread(wq, cpu);
  			if (p) {
  				kthread_bind(p, cpu);
  				wake_up_process(p);
  			} else
  				destroy = 1;
  		}
  	}
  	unlock_cpu_hotplug();
  
  	/*
  	 * Was there any error during startup? If yes then clean up:
  	 */
  	if (destroy) {
  		destroy_workqueue(wq);
  		wq = NULL;
  	}
  	return wq;
  }
  
  static void cleanup_workqueue_thread(struct workqueue_struct *wq, int cpu)
  {
  	struct cpu_workqueue_struct *cwq;
  	unsigned long flags;
  	struct task_struct *p;

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

  	spin_lock_irqsave(&cwq->lock, flags);
  	p = cwq->thread;
  	cwq->thread = NULL;
  	spin_unlock_irqrestore(&cwq->lock, flags);
  	if (p)
  		kthread_stop(p);
  }
  
  void destroy_workqueue(struct workqueue_struct *wq)
  {
  	int cpu;
  
  	flush_workqueue(wq);
  
  	/* We don't need the distraction of CPUs appearing and vanishing. */
  	lock_cpu_hotplug();
  	if (is_single_threaded(wq))
  		cleanup_workqueue_thread(wq, 0);
  	else {
  		for_each_online_cpu(cpu)
  			cleanup_workqueue_thread(wq, cpu);
  		spin_lock(&workqueue_lock);
  		list_del(&wq->list);
  		spin_unlock(&workqueue_lock);
  	}
  	unlock_cpu_hotplug();

  	free_percpu(wq->cpu_wq);

  	kfree(wq);
  }
  
  static struct workqueue_struct *keventd_wq;
  
  int fastcall schedule_work(struct work_struct *work)
  {
  	return queue_work(keventd_wq, work);
  }
  
  int fastcall schedule_delayed_work(struct work_struct *work, unsigned long delay)
  {
  	return queue_delayed_work(keventd_wq, work, delay);
  }
  
  int schedule_delayed_work_on(int cpu,
  			struct work_struct *work, unsigned long delay)
  {
  	int ret = 0;
  	struct timer_list *timer = &work->timer;
  
  	if (!test_and_set_bit(0, &work->pending)) {
  		BUG_ON(timer_pending(timer));
  		BUG_ON(!list_empty(&work->entry));
  		/* This stores keventd_wq for the moment, for the timer_fn */
  		work->wq_data = keventd_wq;
  		timer->expires = jiffies + delay;
  		timer->data = (unsigned long)work;
  		timer->function = delayed_work_timer_fn;
  		add_timer_on(timer, cpu);
  		ret = 1;
  	}
  	return ret;
  }
  
  void flush_scheduled_work(void)
  {
  	flush_workqueue(keventd_wq);
  }
  
  /**
   * cancel_rearming_delayed_workqueue - reliably kill off a delayed
   *			work whose handler rearms the delayed work.
   * @wq:   the controlling workqueue structure
   * @work: the delayed work struct
   */

  void cancel_rearming_delayed_workqueue(struct workqueue_struct *wq,
  				       struct work_struct *work)

  {
  	while (!cancel_delayed_work(work))
  		flush_workqueue(wq);
  }

  EXPORT_SYMBOL(cancel_rearming_delayed_workqueue);

  
  /**
   * cancel_rearming_delayed_work - reliably kill off a delayed keventd
   *			work whose handler rearms the delayed work.
   * @work: the delayed work struct
   */
  void cancel_rearming_delayed_work(struct work_struct *work)
  {
  	cancel_rearming_delayed_workqueue(keventd_wq, work);
  }
  EXPORT_SYMBOL(cancel_rearming_delayed_work);
  
  int keventd_up(void)
  {
  	return keventd_wq != NULL;
  }
  
  int current_is_keventd(void)
  {
  	struct cpu_workqueue_struct *cwq;
  	int cpu = 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;
  
  }
  
  #ifdef CONFIG_HOTPLUG_CPU
  /* Take the work from this (downed) CPU. */
  static void take_over_work(struct workqueue_struct *wq, unsigned int cpu)
  {

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

  	LIST_HEAD(list);
  	struct work_struct *work;
  
  	spin_lock_irq(&cwq->lock);
  	list_splice_init(&cwq->worklist, &list);
  
  	while (!list_empty(&list)) {
  		printk("Taking work for %s
  ", wq->name);
  		work = list_entry(list.next,struct work_struct,entry);
  		list_del(&work->entry);

  		__queue_work(per_cpu_ptr(wq->cpu_wq, smp_processor_id()), work);

  	}
  	spin_unlock_irq(&cwq->lock);
  }
  
  /* We're holding the cpucontrol mutex here */
  static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
  				  unsigned long action,
  				  void *hcpu)
  {
  	unsigned int hotcpu = (unsigned long)hcpu;
  	struct workqueue_struct *wq;
  
  	switch (action) {
  	case CPU_UP_PREPARE:
  		/* Create a new workqueue thread for it. */
  		list_for_each_entry(wq, &workqueues, list) {

  			if (!create_workqueue_thread(wq, hotcpu)) {

  				printk("workqueue for %i failed
  ", hotcpu);
  				return NOTIFY_BAD;
  			}
  		}
  		break;
  
  	case CPU_ONLINE:
  		/* Kick off worker threads. */
  		list_for_each_entry(wq, &workqueues, list) {

  			struct cpu_workqueue_struct *cwq;
  
  			cwq = per_cpu_ptr(wq->cpu_wq, hotcpu);
  			kthread_bind(cwq->thread, hotcpu);
  			wake_up_process(cwq->thread);

  		}
  		break;
  
  	case CPU_UP_CANCELED:
  		list_for_each_entry(wq, &workqueues, list) {
  			/* Unbind so it can run. */

  			kthread_bind(per_cpu_ptr(wq->cpu_wq, hotcpu)->thread,

  				     any_online_cpu(cpu_online_map));

  			cleanup_workqueue_thread(wq, hotcpu);
  		}
  		break;
  
  	case CPU_DEAD:
  		list_for_each_entry(wq, &workqueues, list)
  			cleanup_workqueue_thread(wq, hotcpu);
  		list_for_each_entry(wq, &workqueues, list)
  			take_over_work(wq, hotcpu);
  		break;
  	}
  
  	return NOTIFY_OK;
  }
  #endif
  
  void init_workqueues(void)
  {
  	hotcpu_notifier(workqueue_cpu_callback, 0);
  	keventd_wq = create_workqueue("events");
  	BUG_ON(!keventd_wq);
  }
  
  EXPORT_SYMBOL_GPL(__create_workqueue);
  EXPORT_SYMBOL_GPL(queue_work);
  EXPORT_SYMBOL_GPL(queue_delayed_work);
  EXPORT_SYMBOL_GPL(flush_workqueue);
  EXPORT_SYMBOL_GPL(destroy_workqueue);
  
  EXPORT_SYMBOL(schedule_work);
  EXPORT_SYMBOL(schedule_delayed_work);
  EXPORT_SYMBOL(schedule_delayed_work_on);
  EXPORT_SYMBOL(flush_scheduled_work);