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(v: &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);
40
41 if (parent)
42 closure_put(cl: 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, flags: atomic_sub_return_release(i: v, 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, flags: atomic_dec_return_release(v: &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(head: &wait_list->list);
73
74 /* We first reverse the list to preserve FIFO ordering and fairness */
75 reverse = llist_reverse_order(head: list);
76
77 /* Then do the wakeups */
78 llist_for_each_entry_safe(cl, t, reverse, list) {
79 closure_set_waiting(cl, f: 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(v: &cl->remaining) & CLOSURE_WAITING)
95 return false;
96
97 cl->closure_get_happened = true;
98 closure_set_waiting(cl, _RET_IP_);
99 atomic_add(i: CLOSURE_WAITING + 1, v: &cl->remaining);
100 llist_add(new: &cl->list, head: &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 void closure_sync_fn(struct closure *cl)
112{
113 struct closure_syncer *s = cl->s;
114 struct task_struct *p;
115
116 rcu_read_lock();
117 p = READ_ONCE(s->task);
118 s->done = 1;
119 wake_up_process(tsk: p);
120 rcu_read_unlock();
121}
122
123void __sched __closure_sync(struct closure *cl)
124{
125 struct closure_syncer s = { .task = current };
126
127 cl->s = &s;
128 continue_at(cl, closure_sync_fn, NULL);
129
130 while (1) {
131 set_current_state(TASK_UNINTERRUPTIBLE);
132 if (s.done)
133 break;
134 schedule();
135 }
136
137 __set_current_state(TASK_RUNNING);
138}
139EXPORT_SYMBOL(__closure_sync);
140
141#ifdef CONFIG_DEBUG_CLOSURES
142
143static LIST_HEAD(closure_list);
144static DEFINE_SPINLOCK(closure_list_lock);
145
146void closure_debug_create(struct closure *cl)
147{
148 unsigned long flags;
149
150 BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
151 cl->magic = CLOSURE_MAGIC_ALIVE;
152
153 spin_lock_irqsave(&closure_list_lock, flags);
154 list_add(new: &cl->all, head: &closure_list);
155 spin_unlock_irqrestore(lock: &closure_list_lock, flags);
156}
157EXPORT_SYMBOL(closure_debug_create);
158
159void closure_debug_destroy(struct closure *cl)
160{
161 unsigned long flags;
162
163 BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
164 cl->magic = CLOSURE_MAGIC_DEAD;
165
166 spin_lock_irqsave(&closure_list_lock, flags);
167 list_del(entry: &cl->all);
168 spin_unlock_irqrestore(lock: &closure_list_lock, flags);
169}
170EXPORT_SYMBOL(closure_debug_destroy);
171
172static int debug_show(struct seq_file *f, void *data)
173{
174 struct closure *cl;
175
176 spin_lock_irq(lock: &closure_list_lock);
177
178 list_for_each_entry(cl, &closure_list, all) {
179 int r = atomic_read(v: &cl->remaining);
180
181 seq_printf(m: f, fmt: "%p: %pS -> %pS p %p r %i ",
182 cl, (void *) cl->ip, cl->fn, cl->parent,
183 r & CLOSURE_REMAINING_MASK);
184
185 seq_printf(m: f, fmt: "%s%s\n",
186 test_bit(WORK_STRUCT_PENDING_BIT,
187 work_data_bits(&cl->work)) ? "Q" : "",
188 r & CLOSURE_RUNNING ? "R" : "");
189
190 if (r & CLOSURE_WAITING)
191 seq_printf(m: f, fmt: " W %pS\n",
192 (void *) cl->waiting_on);
193
194 seq_puts(m: f, s: "\n");
195 }
196
197 spin_unlock_irq(lock: &closure_list_lock);
198 return 0;
199}
200
201DEFINE_SHOW_ATTRIBUTE(debug);
202
203static int __init closure_debug_init(void)
204{
205 debugfs_create_file(name: "closures", mode: 0400, NULL, NULL, fops: &debug_fops);
206 return 0;
207}
208late_initcall(closure_debug_init)
209
210#endif
211

source code of linux/lib/closure.c