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
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 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 */
closure_sub(struct closure * cl,int v)44 void closure_sub(struct closure *cl, int v)
45 {
46 closure_put_after_sub(cl, atomic_sub_return(v, &cl->remaining));
47 }
48 EXPORT_SYMBOL(closure_sub);
49
50 /*
51 * closure_put - decrement a closure's refcount
52 */
closure_put(struct closure * cl)53 void closure_put(struct closure *cl)
54 {
55 closure_put_after_sub(cl, atomic_dec_return(&cl->remaining));
56 }
57 EXPORT_SYMBOL(closure_put);
58
59 /*
60 * closure_wake_up - wake up all closures on a wait list, without memory barrier
61 */
__closure_wake_up(struct closure_waitlist * wait_list)62 void __closure_wake_up(struct closure_waitlist *wait_list)
63 {
64 struct llist_node *list;
65 struct closure *cl, *t;
66 struct llist_node *reverse = NULL;
67
68 list = llist_del_all(&wait_list->list);
69
70 /* We first reverse the list to preserve FIFO ordering and fairness */
71 reverse = llist_reverse_order(list);
72
73 /* Then do the wakeups */
74 llist_for_each_entry_safe(cl, t, reverse, list) {
75 closure_set_waiting(cl, 0);
76 closure_sub(cl, CLOSURE_WAITING + 1);
77 }
78 }
79 EXPORT_SYMBOL(__closure_wake_up);
80
81 /**
82 * closure_wait - add a closure to a waitlist
83 * @waitlist: will own a ref on @cl, which will be released when
84 * closure_wake_up() is called on @waitlist.
85 * @cl: closure pointer.
86 *
87 */
closure_wait(struct closure_waitlist * waitlist,struct closure * cl)88 bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
89 {
90 if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
91 return false;
92
93 closure_set_waiting(cl, _RET_IP_);
94 atomic_add(CLOSURE_WAITING + 1, &cl->remaining);
95 llist_add(&cl->list, &waitlist->list);
96
97 return true;
98 }
99 EXPORT_SYMBOL(closure_wait);
100
101 struct closure_syncer {
102 struct task_struct *task;
103 int done;
104 };
105
closure_sync_fn(struct closure * cl)106 static void closure_sync_fn(struct closure *cl)
107 {
108 struct closure_syncer *s = cl->s;
109 struct task_struct *p;
110
111 rcu_read_lock();
112 p = READ_ONCE(s->task);
113 s->done = 1;
114 wake_up_process(p);
115 rcu_read_unlock();
116 }
117
__closure_sync(struct closure * cl)118 void __sched __closure_sync(struct closure *cl)
119 {
120 struct closure_syncer s = { .task = current };
121
122 cl->s = &s;
123 continue_at(cl, closure_sync_fn, NULL);
124
125 while (1) {
126 set_current_state(TASK_UNINTERRUPTIBLE);
127 if (s.done)
128 break;
129 schedule();
130 }
131
132 __set_current_state(TASK_RUNNING);
133 }
134 EXPORT_SYMBOL(__closure_sync);
135
136 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG
137
138 static LIST_HEAD(closure_list);
139 static DEFINE_SPINLOCK(closure_list_lock);
140
closure_debug_create(struct closure * cl)141 void closure_debug_create(struct closure *cl)
142 {
143 unsigned long flags;
144
145 BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
146 cl->magic = CLOSURE_MAGIC_ALIVE;
147
148 spin_lock_irqsave(&closure_list_lock, flags);
149 list_add(&cl->all, &closure_list);
150 spin_unlock_irqrestore(&closure_list_lock, flags);
151 }
152 EXPORT_SYMBOL(closure_debug_create);
153
closure_debug_destroy(struct closure * cl)154 void closure_debug_destroy(struct closure *cl)
155 {
156 unsigned long flags;
157
158 BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
159 cl->magic = CLOSURE_MAGIC_DEAD;
160
161 spin_lock_irqsave(&closure_list_lock, flags);
162 list_del(&cl->all);
163 spin_unlock_irqrestore(&closure_list_lock, flags);
164 }
165 EXPORT_SYMBOL(closure_debug_destroy);
166
167 static struct dentry *closure_debug;
168
debug_seq_show(struct seq_file * f,void * data)169 static int debug_seq_show(struct seq_file *f, void *data)
170 {
171 struct closure *cl;
172
173 spin_lock_irq(&closure_list_lock);
174
175 list_for_each_entry(cl, &closure_list, all) {
176 int r = atomic_read(&cl->remaining);
177
178 seq_printf(f, "%p: %pS -> %pS p %p r %i ",
179 cl, (void *) cl->ip, cl->fn, cl->parent,
180 r & CLOSURE_REMAINING_MASK);
181
182 seq_printf(f, "%s%s\n",
183 test_bit(WORK_STRUCT_PENDING_BIT,
184 work_data_bits(&cl->work)) ? "Q" : "",
185 r & CLOSURE_RUNNING ? "R" : "");
186
187 if (r & CLOSURE_WAITING)
188 seq_printf(f, " W %pS\n",
189 (void *) cl->waiting_on);
190
191 seq_printf(f, "\n");
192 }
193
194 spin_unlock_irq(&closure_list_lock);
195 return 0;
196 }
197
debug_seq_open(struct inode * inode,struct file * file)198 static int debug_seq_open(struct inode *inode, struct file *file)
199 {
200 return single_open(file, debug_seq_show, NULL);
201 }
202
203 static const struct file_operations debug_ops = {
204 .owner = THIS_MODULE,
205 .open = debug_seq_open,
206 .read = seq_read,
207 .release = single_release
208 };
209
closure_debug_init(void)210 void __init closure_debug_init(void)
211 {
212 if (!IS_ERR_OR_NULL(bcache_debug))
213 /*
214 * it is unnecessary to check return value of
215 * debugfs_create_file(), we should not care
216 * about this.
217 */
218 closure_debug = debugfs_create_file(
219 "closures", 0400, bcache_debug, NULL, &debug_ops);
220 }
221 #endif
222
223 MODULE_AUTHOR("Kent Overstreet <koverstreet@google.com>");
224 MODULE_LICENSE("GPL");
225
