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/closure.h>
10#include <linux/debugfs.h>
11#include <linux/export.h>
12#include <linux/rcupdate.h>
13#include <linux/seq_file.h>
14#include <linux/sched/debug.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		smp_acquire__after_ctrl_dep();
25
26		cl->closure_get_happened = false;
27
28		if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {
29			atomic_set(&cl->remaining,
30				   CLOSURE_REMAINING_INITIALIZER);
31			closure_queue(cl);
32		} else {
33			struct closure *parent = cl->parent;
34			closure_fn *destructor = cl->fn;
35
36			closure_debug_destroy(cl);
37
38			if (destructor)
39				destructor(&cl->work);
40
41			if (parent)
42				closure_put(parent);
43		}
44	}
45}
46
47/* For clearing flags with the same atomic op as a put */
48void closure_sub(struct closure *cl, int v)
49{
50	closure_put_after_sub(cl, atomic_sub_return_release(v, &cl->remaining));
51}
52EXPORT_SYMBOL(closure_sub);
53
54/*
55 * closure_put - decrement a closure's refcount
56 */
57void closure_put(struct closure *cl)
58{
59	closure_put_after_sub(cl, atomic_dec_return_release(&cl->remaining));
60}
61EXPORT_SYMBOL(closure_put);
62
63/*
64 * closure_wake_up - wake up all closures on a wait list, without memory barrier
65 */
66void __closure_wake_up(struct closure_waitlist *wait_list)
67{
68	struct llist_node *list;
69	struct closure *cl, *t;
70	struct llist_node *reverse = NULL;
71
72	list = llist_del_all(&wait_list->list);
73
74	/* We first reverse the list to preserve FIFO ordering and fairness */
75	reverse = llist_reverse_order(list);
76
77	/* Then do the wakeups */
78	llist_for_each_entry_safe(cl, t, reverse, list) {
79		closure_set_waiting(cl, 0);
80		closure_sub(cl, CLOSURE_WAITING + 1);
81	}
82}
83EXPORT_SYMBOL(__closure_wake_up);
84
85/**
86 * closure_wait - add a closure to a waitlist
87 * @waitlist: will own a ref on @cl, which will be released when
88 * closure_wake_up() is called on @waitlist.
89 * @cl: closure pointer.
90 *
91 */
92bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
93{
94	if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
95		return false;
96
97	cl->closure_get_happened = true;
98	closure_set_waiting(cl, _RET_IP_);
99	atomic_add(CLOSURE_WAITING + 1, &cl->remaining);
100	llist_add(&cl->list, &waitlist->list);
101
102	return true;
103}
104EXPORT_SYMBOL(closure_wait);
105
106struct closure_syncer {
107	struct task_struct	*task;
108	int			done;
109};
110
111static CLOSURE_CALLBACK(closure_sync_fn)
112{
113	struct closure *cl = container_of(ws, struct closure, work);
114	struct closure_syncer *s = cl->s;
115	struct task_struct *p;
116
117	rcu_read_lock();
118	p = READ_ONCE(s->task);
119	s->done = 1;
120	wake_up_process(p);
121	rcu_read_unlock();
122}
123
124void __sched __closure_sync(struct closure *cl)
125{
126	struct closure_syncer s = { .task = current };
127
128	cl->s = &s;
129	continue_at(cl, closure_sync_fn, NULL);
130
131	while (1) {
132		set_current_state(TASK_UNINTERRUPTIBLE);
133		if (s.done)
134			break;
135		schedule();
136	}
137
138	__set_current_state(TASK_RUNNING);
139}
140EXPORT_SYMBOL(__closure_sync);
141
142#ifdef CONFIG_DEBUG_CLOSURES
143
144static LIST_HEAD(closure_list);
145static DEFINE_SPINLOCK(closure_list_lock);
146
147void closure_debug_create(struct closure *cl)
148{
149	unsigned long flags;
150
151	BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
152	cl->magic = CLOSURE_MAGIC_ALIVE;
153
154	spin_lock_irqsave(&closure_list_lock, flags);
155	list_add(&cl->all, &closure_list);
156	spin_unlock_irqrestore(&closure_list_lock, flags);
157}
158EXPORT_SYMBOL(closure_debug_create);
159
160void closure_debug_destroy(struct closure *cl)
161{
162	unsigned long flags;
163
164	BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
165	cl->magic = CLOSURE_MAGIC_DEAD;
166
167	spin_lock_irqsave(&closure_list_lock, flags);
168	list_del(&cl->all);
169	spin_unlock_irqrestore(&closure_list_lock, flags);
170}
171EXPORT_SYMBOL(closure_debug_destroy);
172
173static int debug_show(struct seq_file *f, void *data)
174{
175	struct closure *cl;
176
177	spin_lock_irq(&closure_list_lock);
178
179	list_for_each_entry(cl, &closure_list, all) {
180		int r = atomic_read(&cl->remaining);
181
182		seq_printf(f, "%p: %pS -> %pS p %p r %i ",
183			   cl, (void *) cl->ip, cl->fn, cl->parent,
184			   r & CLOSURE_REMAINING_MASK);
185
186		seq_printf(f, "%s%s\n",
187			   test_bit(WORK_STRUCT_PENDING_BIT,
188				    work_data_bits(&cl->work)) ? "Q" : "",
189			   r & CLOSURE_RUNNING	? "R" : "");
190
191		if (r & CLOSURE_WAITING)
192			seq_printf(f, " W %pS\n",
193				   (void *) cl->waiting_on);
194
195		seq_puts(f, "\n");
196	}
197
198	spin_unlock_irq(&closure_list_lock);
199	return 0;
200}
201
202DEFINE_SHOW_ATTRIBUTE(debug);
203
204static int __init closure_debug_init(void)
205{
206	debugfs_create_file("closures", 0400, NULL, NULL, &debug_fops);
207	return 0;
208}
209late_initcall(closure_debug_init)
210
211#endif
212