1/*
2 * Asynchronous refcounty things
3 *
4 * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
5 * Copyright 2012 Google, Inc.
6 */
7
8#include <linux/debugfs.h>
9#include <linux/module.h>
10#include <linux/seq_file.h>
11
12#include "closure.h"
13
14static inline void closure_put_after_sub(struct closure *cl, int flags)
15{
16	int r = flags & CLOSURE_REMAINING_MASK;
17
18	BUG_ON(flags & CLOSURE_GUARD_MASK);
19	BUG_ON(!r && (flags & ~CLOSURE_DESTRUCTOR));
20
21	/* Must deliver precisely one wakeup */
22	if (r == 1 && (flags & CLOSURE_SLEEPING))
23		wake_up_process(cl->task);
24
25	if (!r) {
26		if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {
27			atomic_set(&cl->remaining,
28				   CLOSURE_REMAINING_INITIALIZER);
29			closure_queue(cl);
30		} else {
31			struct closure *parent = cl->parent;
32			closure_fn *destructor = cl->fn;
33
34			closure_debug_destroy(cl);
35
36			if (destructor)
37				destructor(cl);
38
39			if (parent)
40				closure_put(parent);
41		}
42	}
43}
44
45/* For clearing flags with the same atomic op as a put */
46void closure_sub(struct closure *cl, int v)
47{
48	closure_put_after_sub(cl, atomic_sub_return(v, &cl->remaining));
49}
50EXPORT_SYMBOL(closure_sub);
51
52/**
53 * closure_put - decrement a closure's refcount
54 */
55void closure_put(struct closure *cl)
56{
57	closure_put_after_sub(cl, atomic_dec_return(&cl->remaining));
58}
59EXPORT_SYMBOL(closure_put);
60
61/**
62 * closure_wake_up - wake up all closures on a wait list, without memory barrier
63 */
64void __closure_wake_up(struct closure_waitlist *wait_list)
65{
66	struct llist_node *list;
67	struct closure *cl;
68	struct llist_node *reverse = NULL;
69
70	list = llist_del_all(&wait_list->list);
71
72	/* We first reverse the list to preserve FIFO ordering and fairness */
73
74	while (list) {
75		struct llist_node *t = list;
76		list = llist_next(list);
77
78		t->next = reverse;
79		reverse = t;
80	}
81
82	/* Then do the wakeups */
83
84	while (reverse) {
85		cl = container_of(reverse, struct closure, list);
86		reverse = llist_next(reverse);
87
88		closure_set_waiting(cl, 0);
89		closure_sub(cl, CLOSURE_WAITING + 1);
90	}
91}
92EXPORT_SYMBOL(__closure_wake_up);
93
94/**
95 * closure_wait - add a closure to a waitlist
96 *
97 * @waitlist will own a ref on @cl, which will be released when
98 * closure_wake_up() is called on @waitlist.
99 *
100 */
101bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
102{
103	if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
104		return false;
105
106	closure_set_waiting(cl, _RET_IP_);
107	atomic_add(CLOSURE_WAITING + 1, &cl->remaining);
108	llist_add(&cl->list, &waitlist->list);
109
110	return true;
111}
112EXPORT_SYMBOL(closure_wait);
113
114/**
115 * closure_sync - sleep until a closure a closure has nothing left to wait on
116 *
117 * Sleeps until the refcount hits 1 - the thread that's running the closure owns
118 * the last refcount.
119 */
120void closure_sync(struct closure *cl)
121{
122	while (1) {
123		__closure_start_sleep(cl);
124		closure_set_ret_ip(cl);
125
126		if ((atomic_read(&cl->remaining) &
127		     CLOSURE_REMAINING_MASK) == 1)
128			break;
129
130		schedule();
131	}
132
133	__closure_end_sleep(cl);
134}
135EXPORT_SYMBOL(closure_sync);
136
137#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
138
139static LIST_HEAD(closure_list);
140static DEFINE_SPINLOCK(closure_list_lock);
141
142void closure_debug_create(struct closure *cl)
143{
144	unsigned long flags;
145
146	BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
147	cl->magic = CLOSURE_MAGIC_ALIVE;
148
149	spin_lock_irqsave(&closure_list_lock, flags);
150	list_add(&cl->all, &closure_list);
151	spin_unlock_irqrestore(&closure_list_lock, flags);
152}
153EXPORT_SYMBOL(closure_debug_create);
154
155void closure_debug_destroy(struct closure *cl)
156{
157	unsigned long flags;
158
159	BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
160	cl->magic = CLOSURE_MAGIC_DEAD;
161
162	spin_lock_irqsave(&closure_list_lock, flags);
163	list_del(&cl->all);
164	spin_unlock_irqrestore(&closure_list_lock, flags);
165}
166EXPORT_SYMBOL(closure_debug_destroy);
167
168static struct dentry *debug;
169
170static int debug_seq_show(struct seq_file *f, void *data)
171{
172	struct closure *cl;
173	spin_lock_irq(&closure_list_lock);
174
175	list_for_each_entry(cl, &closure_list, all) {
176		int r = atomic_read(&cl->remaining);
177
178		seq_printf(f, "%p: %pF -> %pf p %p r %i ",
179			   cl, (void *) cl->ip, cl->fn, cl->parent,
180			   r & CLOSURE_REMAINING_MASK);
181
182		seq_printf(f, "%s%s%s%s\n",
183			   test_bit(WORK_STRUCT_PENDING_BIT,
184				    work_data_bits(&cl->work)) ? "Q" : "",
185			   r & CLOSURE_RUNNING	? "R" : "",
186			   r & CLOSURE_STACK	? "S" : "",
187			   r & CLOSURE_SLEEPING	? "Sl" : "");
188
189		if (r & CLOSURE_WAITING)
190			seq_printf(f, " W %pF\n",
191				   (void *) cl->waiting_on);
192
193		seq_printf(f, "\n");
194	}
195
196	spin_unlock_irq(&closure_list_lock);
197	return 0;
198}
199
200static int debug_seq_open(struct inode *inode, struct file *file)
201{
202	return single_open(file, debug_seq_show, NULL);
203}
204
205static const struct file_operations debug_ops = {
206	.owner		= THIS_MODULE,
207	.open		= debug_seq_open,
208	.read		= seq_read,
209	.release	= single_release
210};
211
212void __init closure_debug_init(void)
213{
214	debug = debugfs_create_file("closures", 0400, NULL, NULL, &debug_ops);
215}
216
217#endif
218
219MODULE_AUTHOR("Kent Overstreet <koverstreet@google.com>");
220MODULE_LICENSE("GPL");
221