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
closure_put_after_sub(struct closure * cl,int flags)16 static 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 */
closure_sub(struct closure * cl,int v)48 void closure_sub(struct closure *cl, int v)
49 {
50 closure_put_after_sub(cl, atomic_sub_return_release(v, &cl->remaining));
51 }
52 EXPORT_SYMBOL(closure_sub);
53
54 /*
55 * closure_put - decrement a closure's refcount
56 */
closure_put(struct closure * cl)57 void closure_put(struct closure *cl)
58 {
59 closure_put_after_sub(cl, atomic_dec_return_release(&cl->remaining));
60 }
61 EXPORT_SYMBOL(closure_put);
62
63 /*
64 * closure_wake_up - wake up all closures on a wait list, without memory barrier
65 */
__closure_wake_up(struct closure_waitlist * wait_list)66 void __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 }
83 EXPORT_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 */
closure_wait(struct closure_waitlist * waitlist,struct closure * cl)92 bool 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 }
104 EXPORT_SYMBOL(closure_wait);
105
106 struct closure_syncer {
107 struct task_struct *task;
108 int done;
109 };
110
CLOSURE_CALLBACK(closure_sync_fn)111 static 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
__closure_sync(struct closure * cl)124 void __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 }
140 EXPORT_SYMBOL(__closure_sync);
141
142 #ifdef CONFIG_DEBUG_CLOSURES
143
144 static LIST_HEAD(closure_list);
145 static DEFINE_SPINLOCK(closure_list_lock);
146
closure_debug_create(struct closure * cl)147 void 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 }
158 EXPORT_SYMBOL(closure_debug_create);
159
closure_debug_destroy(struct closure * cl)160 void 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 }
171 EXPORT_SYMBOL(closure_debug_destroy);
172
debug_show(struct seq_file * f,void * data)173 static 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
202 DEFINE_SHOW_ATTRIBUTE(debug);
203
closure_debug_init(void)204 static int __init closure_debug_init(void)
205 {
206 debugfs_create_file("closures", 0400, NULL, NULL, &debug_fops);
207 return 0;
208 }
209 late_initcall(closure_debug_init)
210
211 #endif
212