/*
   * Asynchronous refcounty things
   *
   * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
   * Copyright 2012 Google, Inc.
   */
  
  #include <linux/debugfs.h>
  #include <linux/module.h>
  #include <linux/seq_file.h>
  
  #include "closure.h"
  
  static inline void closure_put_after_sub(struct closure *cl, int flags)
  {
  	int r = flags & CLOSURE_REMAINING_MASK;
  
  	BUG_ON(flags & CLOSURE_GUARD_MASK);
  	BUG_ON(!r && (flags & ~CLOSURE_DESTRUCTOR));
  
  	/* Must deliver precisely one wakeup */
  	if (r == 1 && (flags & CLOSURE_SLEEPING))
  		wake_up_process(cl->task);
  
  	if (!r) {
  		if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {
  			atomic_set(&cl->remaining,
  				   CLOSURE_REMAINING_INITIALIZER);
  			closure_queue(cl);
  		} else {
  			struct closure *parent = cl->parent;
  			closure_fn *destructor = cl->fn;
  
  			closure_debug_destroy(cl);
  
  			if (destructor)
  				destructor(cl);
  
  			if (parent)
  				closure_put(parent);
  		}
  	}
  }
  
  /* For clearing flags with the same atomic op as a put */
  void closure_sub(struct closure *cl, int v)
  {
  	closure_put_after_sub(cl, atomic_sub_return(v, &cl->remaining));
  }
  EXPORT_SYMBOL(closure_sub);
  
  /**
   * closure_put - decrement a closure's refcount
   */
  void closure_put(struct closure *cl)
  {
  	closure_put_after_sub(cl, atomic_dec_return(&cl->remaining));
  }
  EXPORT_SYMBOL(closure_put);
  
  /**
   * closure_wake_up - wake up all closures on a wait list, without memory barrier
   */
  void __closure_wake_up(struct closure_waitlist *wait_list)
  {
  	struct llist_node *list;
  	struct closure *cl;
  	struct llist_node *reverse = NULL;
  
  	list = llist_del_all(&wait_list->list);
  
  	/* We first reverse the list to preserve FIFO ordering and fairness */
  
  	while (list) {
  		struct llist_node *t = list;
  		list = llist_next(list);
  
  		t->next = reverse;
  		reverse = t;
  	}
  
  	/* Then do the wakeups */
  
  	while (reverse) {
  		cl = container_of(reverse, struct closure, list);
  		reverse = llist_next(reverse);
  
  		closure_set_waiting(cl, 0);
  		closure_sub(cl, CLOSURE_WAITING + 1);
  	}
  }
  EXPORT_SYMBOL(__closure_wake_up);
  
  /**
   * closure_wait - add a closure to a waitlist
   *
   * @waitlist will own a ref on @cl, which will be released when
   * closure_wake_up() is called on @waitlist.
   *
   */
  bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
  {
  	if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
  		return false;
  
  	closure_set_waiting(cl, _RET_IP_);
  	atomic_add(CLOSURE_WAITING + 1, &cl->remaining);
  	llist_add(&cl->list, &waitlist->list);
  
  	return true;
  }
  EXPORT_SYMBOL(closure_wait);
  
  /**
   * closure_sync - sleep until a closure a closure has nothing left to wait on
   *
   * Sleeps until the refcount hits 1 - the thread that's running the closure owns
   * the last refcount.
   */
  void closure_sync(struct closure *cl)
  {
  	while (1) {
  		__closure_start_sleep(cl);
  		closure_set_ret_ip(cl);
  
  		if ((atomic_read(&cl->remaining) &
  		     CLOSURE_REMAINING_MASK) == 1)
  			break;
  
  		schedule();
  	}
  
  	__closure_end_sleep(cl);
  }
  EXPORT_SYMBOL(closure_sync);
  
  #ifdef CONFIG_BCACHE_CLOSURES_DEBUG
  
  static LIST_HEAD(closure_list);
  static DEFINE_SPINLOCK(closure_list_lock);
  
  void closure_debug_create(struct closure *cl)
  {
  	unsigned long flags;
  
  	BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
  	cl->magic = CLOSURE_MAGIC_ALIVE;
  
  	spin_lock_irqsave(&closure_list_lock, flags);
  	list_add(&cl->all, &closure_list);
  	spin_unlock_irqrestore(&closure_list_lock, flags);
  }
  EXPORT_SYMBOL(closure_debug_create);
  
  void closure_debug_destroy(struct closure *cl)
  {
  	unsigned long flags;
  
  	BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
  	cl->magic = CLOSURE_MAGIC_DEAD;
  
  	spin_lock_irqsave(&closure_list_lock, flags);
  	list_del(&cl->all);
  	spin_unlock_irqrestore(&closure_list_lock, flags);
  }
  EXPORT_SYMBOL(closure_debug_destroy);
  
  static struct dentry *debug;
  
  #define work_data_bits(work) ((unsigned long *)(&(work)->data))
  
  static int debug_seq_show(struct seq_file *f, void *data)
  {
  	struct closure *cl;
  	spin_lock_irq(&closure_list_lock);
  
  	list_for_each_entry(cl, &closure_list, all) {
  		int r = atomic_read(&cl->remaining);
  
  		seq_printf(f, "%p: %pF -> %pf p %p r %i ",
  			   cl, (void *) cl->ip, cl->fn, cl->parent,
  			   r & CLOSURE_REMAINING_MASK);
  
  		seq_printf(f, "%s%s%s%s
  ",
  			   test_bit(WORK_STRUCT_PENDING,
  				    work_data_bits(&cl->work)) ? "Q" : "",
  			   r & CLOSURE_RUNNING	? "R" : "",
  			   r & CLOSURE_STACK	? "S" : "",
  			   r & CLOSURE_SLEEPING	? "Sl" : "");
  
  		if (r & CLOSURE_WAITING)
  			seq_printf(f, " W %pF
  ",
  				   (void *) cl->waiting_on);
  
  		seq_printf(f, "
  ");
  	}
  
  	spin_unlock_irq(&closure_list_lock);
  	return 0;
  }
  
  static int debug_seq_open(struct inode *inode, struct file *file)
  {
  	return single_open(file, debug_seq_show, NULL);
  }
  
  static const struct file_operations debug_ops = {
  	.owner		= THIS_MODULE,
  	.open		= debug_seq_open,
  	.read		= seq_read,
  	.release	= single_release
  };
  
  void __init closure_debug_init(void)
  {
  	debug = debugfs_create_file("closures", 0400, NULL, NULL, &debug_ops);
  }
  
  #endif
  
  MODULE_AUTHOR("Kent Overstreet <koverstreet@google.com>");
  MODULE_LICENSE("GPL");