1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Asynchronous refcounty things
4 *
5 * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
6 * Copyright 2012 Google, Inc.
7 */
8
9#include <linux/debugfs.h>
10#include <linux/module.h>
11#include <linux/seq_file.h>
12#include <linux/sched/debug.h>
13
14#include "closure.h"
15
16static inline void closure_put_after_sub(struct closure *cl, int flags)
17{
18	int r = flags & CLOSURE_REMAINING_MASK;
19
20	BUG_ON(flags & CLOSURE_GUARD_MASK);
21	BUG_ON(!r && (flags & ~CLOSURE_DESTRUCTOR));
22
23	if (!r) {
24		if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {
25			atomic_set(&cl->remaining,
26				   CLOSURE_REMAINING_INITIALIZER);
27			closure_queue(cl);
28		} else {
29			struct closure *parent = cl->parent;
30			closure_fn *destructor = cl->fn;
31
32			closure_debug_destroy(cl);
33
34			if (destructor)
35				destructor(cl);
36
37			if (parent)
38				closure_put(parent);
39		}
40	}
41}
42
43/* For clearing flags with the same atomic op as a put */
44void closure_sub(struct closure *cl, int v)
45{
46	closure_put_after_sub(cl, atomic_sub_return(v, &cl->remaining));
47}
48
49/*
50 * closure_put - decrement a closure's refcount
51 */
52void closure_put(struct closure *cl)
53{
54	closure_put_after_sub(cl, atomic_dec_return(&cl->remaining));
55}
56
57/*
58 * closure_wake_up - wake up all closures on a wait list, without memory barrier
59 */
60void __closure_wake_up(struct closure_waitlist *wait_list)
61{
62	struct llist_node *list;
63	struct closure *cl, *t;
64	struct llist_node *reverse = NULL;
65
66	list = llist_del_all(&wait_list->list);
67
68	/* We first reverse the list to preserve FIFO ordering and fairness */
69	reverse = llist_reverse_order(list);
70
71	/* Then do the wakeups */
72	llist_for_each_entry_safe(cl, t, reverse, list) {
73		closure_set_waiting(cl, 0);
74		closure_sub(cl, CLOSURE_WAITING + 1);
75	}
76}
77
78/**
79 * closure_wait - add a closure to a waitlist
80 * @waitlist: will own a ref on @cl, which will be released when
81 * closure_wake_up() is called on @waitlist.
82 * @cl: closure pointer.
83 *
84 */
85bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
86{
87	if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
88		return false;
89
90	closure_set_waiting(cl, _RET_IP_);
91	atomic_add(CLOSURE_WAITING + 1, &cl->remaining);
92	llist_add(&cl->list, &waitlist->list);
93
94	return true;
95}
96
97struct closure_syncer {
98	struct task_struct	*task;
99	int			done;
100};
101
102static void closure_sync_fn(struct closure *cl)
103{
104	struct closure_syncer *s = cl->s;
105	struct task_struct *p;
106
107	rcu_read_lock();
108	p = READ_ONCE(s->task);
109	s->done = 1;
110	wake_up_process(p);
111	rcu_read_unlock();
112}
113
114void __sched __closure_sync(struct closure *cl)
115{
116	struct closure_syncer s = { .task = current };
117
118	cl->s = &s;
119	continue_at(cl, closure_sync_fn, NULL);
120
121	while (1) {
122		set_current_state(TASK_UNINTERRUPTIBLE);
123		if (s.done)
124			break;
125		schedule();
126	}
127
128	__set_current_state(TASK_RUNNING);
129}
130
131#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
132
133static LIST_HEAD(closure_list);
134static DEFINE_SPINLOCK(closure_list_lock);
135
136void closure_debug_create(struct closure *cl)
137{
138	unsigned long flags;
139
140	BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
141	cl->magic = CLOSURE_MAGIC_ALIVE;
142
143	spin_lock_irqsave(&closure_list_lock, flags);
144	list_add(&cl->all, &closure_list);
145	spin_unlock_irqrestore(&closure_list_lock, flags);
146}
147
148void closure_debug_destroy(struct closure *cl)
149{
150	unsigned long flags;
151
152	BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
153	cl->magic = CLOSURE_MAGIC_DEAD;
154
155	spin_lock_irqsave(&closure_list_lock, flags);
156	list_del(&cl->all);
157	spin_unlock_irqrestore(&closure_list_lock, flags);
158}
159
160static struct dentry *closure_debug;
161
162static int debug_show(struct seq_file *f, void *data)
163{
164	struct closure *cl;
165
166	spin_lock_irq(&closure_list_lock);
167
168	list_for_each_entry(cl, &closure_list, all) {
169		int r = atomic_read(&cl->remaining);
170
171		seq_printf(f, "%p: %pS -> %pS p %p r %i ",
172			   cl, (void *) cl->ip, cl->fn, cl->parent,
173			   r & CLOSURE_REMAINING_MASK);
174
175		seq_printf(f, "%s%s\n",
176			   test_bit(WORK_STRUCT_PENDING_BIT,
177				    work_data_bits(&cl->work)) ? "Q" : "",
178			   r & CLOSURE_RUNNING	? "R" : "");
179
180		if (r & CLOSURE_WAITING)
181			seq_printf(f, " W %pS\n",
182				   (void *) cl->waiting_on);
183
184		seq_printf(f, "\n");
185	}
186
187	spin_unlock_irq(&closure_list_lock);
188	return 0;
189}
190
191DEFINE_SHOW_ATTRIBUTE(debug);
192
193void  __init closure_debug_init(void)
194{
195	if (!IS_ERR_OR_NULL(bcache_debug))
196		/*
197		 * it is unnecessary to check return value of
198		 * debugfs_create_file(), we should not care
199		 * about this.
200		 */
201		closure_debug = debugfs_create_file(
202			"closures", 0400, bcache_debug, NULL, &debug_fops);
203}
204#endif
205
206MODULE_AUTHOR("Kent Overstreet <koverstreet@google.com>");
207MODULE_LICENSE("GPL");
208