1 /*
2 * Asynchronous refcounty things
3 *
4 * Copyright 2010, 2011 Kent Overstreet <kent.overstreet@gmail.com>
5 * Copyright 2012 Google, Inc.
6 */
7
8 #include <linux/debugfs.h>
9 #include <linux/module.h>
10 #include <linux/seq_file.h>
11
12 #include "closure.h"
13
closure_put_after_sub(struct closure * cl,int flags)14 static inline void closure_put_after_sub(struct closure *cl, int flags)
15 {
16 int r = flags & CLOSURE_REMAINING_MASK;
17
18 BUG_ON(flags & CLOSURE_GUARD_MASK);
19 BUG_ON(!r && (flags & ~CLOSURE_DESTRUCTOR));
20
21 /* Must deliver precisely one wakeup */
22 if (r == 1 && (flags & CLOSURE_SLEEPING))
23 wake_up_process(cl->task);
24
25 if (!r) {
26 if (cl->fn && !(flags & CLOSURE_DESTRUCTOR)) {
27 atomic_set(&cl->remaining,
28 CLOSURE_REMAINING_INITIALIZER);
29 closure_queue(cl);
30 } else {
31 struct closure *parent = cl->parent;
32 closure_fn *destructor = cl->fn;
33
34 closure_debug_destroy(cl);
35
36 if (destructor)
37 destructor(cl);
38
39 if (parent)
40 closure_put(parent);
41 }
42 }
43 }
44
45 /* For clearing flags with the same atomic op as a put */
closure_sub(struct closure * cl,int v)46 void closure_sub(struct closure *cl, int v)
47 {
48 closure_put_after_sub(cl, atomic_sub_return(v, &cl->remaining));
49 }
50 EXPORT_SYMBOL(closure_sub);
51
52 /**
53 * closure_put - decrement a closure's refcount
54 */
closure_put(struct closure * cl)55 void closure_put(struct closure *cl)
56 {
57 closure_put_after_sub(cl, atomic_dec_return(&cl->remaining));
58 }
59 EXPORT_SYMBOL(closure_put);
60
61 /**
62 * closure_wake_up - wake up all closures on a wait list, without memory barrier
63 */
__closure_wake_up(struct closure_waitlist * wait_list)64 void __closure_wake_up(struct closure_waitlist *wait_list)
65 {
66 struct llist_node *list;
67 struct closure *cl;
68 struct llist_node *reverse = NULL;
69
70 list = llist_del_all(&wait_list->list);
71
72 /* We first reverse the list to preserve FIFO ordering and fairness */
73
74 while (list) {
75 struct llist_node *t = list;
76 list = llist_next(list);
77
78 t->next = reverse;
79 reverse = t;
80 }
81
82 /* Then do the wakeups */
83
84 while (reverse) {
85 cl = container_of(reverse, struct closure, list);
86 reverse = llist_next(reverse);
87
88 closure_set_waiting(cl, 0);
89 closure_sub(cl, CLOSURE_WAITING + 1);
90 }
91 }
92 EXPORT_SYMBOL(__closure_wake_up);
93
94 /**
95 * closure_wait - add a closure to a waitlist
96 *
97 * @waitlist will own a ref on @cl, which will be released when
98 * closure_wake_up() is called on @waitlist.
99 *
100 */
closure_wait(struct closure_waitlist * waitlist,struct closure * cl)101 bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
102 {
103 if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
104 return false;
105
106 closure_set_waiting(cl, _RET_IP_);
107 atomic_add(CLOSURE_WAITING + 1, &cl->remaining);
108 llist_add(&cl->list, &waitlist->list);
109
110 return true;
111 }
112 EXPORT_SYMBOL(closure_wait);
113
114 /**
115 * closure_sync - sleep until a closure has nothing left to wait on
116 *
117 * Sleeps until the refcount hits 1 - the thread that's running the closure owns
118 * the last refcount.
119 */
closure_sync(struct closure * cl)120 void closure_sync(struct closure *cl)
121 {
122 while (1) {
123 __closure_start_sleep(cl);
124 closure_set_ret_ip(cl);
125
126 if ((atomic_read(&cl->remaining) &
127 CLOSURE_REMAINING_MASK) == 1)
128 break;
129
130 schedule();
131 }
132
133 __closure_end_sleep(cl);
134 }
135 EXPORT_SYMBOL(closure_sync);
136
137 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG
138
139 static LIST_HEAD(closure_list);
140 static DEFINE_SPINLOCK(closure_list_lock);
141
closure_debug_create(struct closure * cl)142 void closure_debug_create(struct closure *cl)
143 {
144 unsigned long flags;
145
146 BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
147 cl->magic = CLOSURE_MAGIC_ALIVE;
148
149 spin_lock_irqsave(&closure_list_lock, flags);
150 list_add(&cl->all, &closure_list);
151 spin_unlock_irqrestore(&closure_list_lock, flags);
152 }
153 EXPORT_SYMBOL(closure_debug_create);
154
closure_debug_destroy(struct closure * cl)155 void closure_debug_destroy(struct closure *cl)
156 {
157 unsigned long flags;
158
159 BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
160 cl->magic = CLOSURE_MAGIC_DEAD;
161
162 spin_lock_irqsave(&closure_list_lock, flags);
163 list_del(&cl->all);
164 spin_unlock_irqrestore(&closure_list_lock, flags);
165 }
166 EXPORT_SYMBOL(closure_debug_destroy);
167
168 static struct dentry *debug;
169
debug_seq_show(struct seq_file * f,void * data)170 static int debug_seq_show(struct seq_file *f, void *data)
171 {
172 struct closure *cl;
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: %pF -> %pf 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%s%s\n",
183 test_bit(WORK_STRUCT_PENDING_BIT,
184 work_data_bits(&cl->work)) ? "Q" : "",
185 r & CLOSURE_RUNNING ? "R" : "",
186 r & CLOSURE_STACK ? "S" : "",
187 r & CLOSURE_SLEEPING ? "Sl" : "");
188
189 if (r & CLOSURE_WAITING)
190 seq_printf(f, " W %pF\n",
191 (void *) cl->waiting_on);
192
193 seq_printf(f, "\n");
194 }
195
196 spin_unlock_irq(&closure_list_lock);
197 return 0;
198 }
199
debug_seq_open(struct inode * inode,struct file * file)200 static int debug_seq_open(struct inode *inode, struct file *file)
201 {
202 return single_open(file, debug_seq_show, NULL);
203 }
204
205 static const struct file_operations debug_ops = {
206 .owner = THIS_MODULE,
207 .open = debug_seq_open,
208 .read = seq_read,
209 .release = single_release
210 };
211
closure_debug_init(void)212 void __init closure_debug_init(void)
213 {
214 debug = debugfs_create_file("closures", 0400, NULL, NULL, &debug_ops);
215 }
216
217 #endif
218
219 MODULE_AUTHOR("Kent Overstreet <koverstreet@google.com>");
220 MODULE_LICENSE("GPL");
221