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->work);
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 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(tsk: 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(new: &cl->all, head: &closure_list);
156 spin_unlock_irqrestore(lock: &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(entry: &cl->all);
169 spin_unlock_irqrestore(lock: &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(lock: &closure_list_lock);
178
179 list_for_each_entry(cl, &closure_list, all) {
180 int r = atomic_read(v: &cl->remaining);
181
182 seq_printf(m: f, fmt: "%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(m: f, fmt: "%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(m: f, fmt: " W %pS\n",
193 (void *) cl->waiting_on);
194
195 seq_puts(m: f, s: "\n");
196 }
197
198 spin_unlock_irq(lock: &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(name: "closures", mode: 0400, NULL, NULL, fops: &debug_fops);
207 return 0;
208}
209late_initcall(closure_debug_init)
210
211#endif
212

source code of linux/lib/closure.c