/*
 * 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 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;

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\n",
                           test_bit(WORK_STRUCT_PENDING_BIT,
                                    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\n",
                                   (void *) cl->waiting_on);

                seq_printf(f, "\n");
        }

        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");