xref: /openbmc/linux/drivers/md/bcache/closure.c (revision 612a462a)
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 
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 */
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  */
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  */
64 void __closure_wake_up(struct closure_waitlist *wait_list)
65 {
66 	struct llist_node *list;
67 	struct closure *cl, *t;
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 	reverse = llist_reverse_order(list);
74 
75 	/* Then do the wakeups */
76 	llist_for_each_entry_safe(cl, t, reverse, list) {
77 		closure_set_waiting(cl, 0);
78 		closure_sub(cl, CLOSURE_WAITING + 1);
79 	}
80 }
81 EXPORT_SYMBOL(__closure_wake_up);
82 
83 /**
84  * closure_wait - add a closure to a waitlist
85  *
86  * @waitlist will own a ref on @cl, which will be released when
87  * closure_wake_up() is called on @waitlist.
88  *
89  */
90 bool closure_wait(struct closure_waitlist *waitlist, struct closure *cl)
91 {
92 	if (atomic_read(&cl->remaining) & CLOSURE_WAITING)
93 		return false;
94 
95 	closure_set_waiting(cl, _RET_IP_);
96 	atomic_add(CLOSURE_WAITING + 1, &cl->remaining);
97 	llist_add(&cl->list, &waitlist->list);
98 
99 	return true;
100 }
101 EXPORT_SYMBOL(closure_wait);
102 
103 /**
104  * closure_sync - sleep until a closure has nothing left to wait on
105  *
106  * Sleeps until the refcount hits 1 - the thread that's running the closure owns
107  * the last refcount.
108  */
109 void closure_sync(struct closure *cl)
110 {
111 	while (1) {
112 		__closure_start_sleep(cl);
113 		closure_set_ret_ip(cl);
114 
115 		if ((atomic_read(&cl->remaining) &
116 		     CLOSURE_REMAINING_MASK) == 1)
117 			break;
118 
119 		schedule();
120 	}
121 
122 	__closure_end_sleep(cl);
123 }
124 EXPORT_SYMBOL(closure_sync);
125 
126 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG
127 
128 static LIST_HEAD(closure_list);
129 static DEFINE_SPINLOCK(closure_list_lock);
130 
131 void closure_debug_create(struct closure *cl)
132 {
133 	unsigned long flags;
134 
135 	BUG_ON(cl->magic == CLOSURE_MAGIC_ALIVE);
136 	cl->magic = CLOSURE_MAGIC_ALIVE;
137 
138 	spin_lock_irqsave(&closure_list_lock, flags);
139 	list_add(&cl->all, &closure_list);
140 	spin_unlock_irqrestore(&closure_list_lock, flags);
141 }
142 EXPORT_SYMBOL(closure_debug_create);
143 
144 void closure_debug_destroy(struct closure *cl)
145 {
146 	unsigned long flags;
147 
148 	BUG_ON(cl->magic != CLOSURE_MAGIC_ALIVE);
149 	cl->magic = CLOSURE_MAGIC_DEAD;
150 
151 	spin_lock_irqsave(&closure_list_lock, flags);
152 	list_del(&cl->all);
153 	spin_unlock_irqrestore(&closure_list_lock, flags);
154 }
155 EXPORT_SYMBOL(closure_debug_destroy);
156 
157 static struct dentry *debug;
158 
159 static int debug_seq_show(struct seq_file *f, void *data)
160 {
161 	struct closure *cl;
162 	spin_lock_irq(&closure_list_lock);
163 
164 	list_for_each_entry(cl, &closure_list, all) {
165 		int r = atomic_read(&cl->remaining);
166 
167 		seq_printf(f, "%p: %pF -> %pf p %p r %i ",
168 			   cl, (void *) cl->ip, cl->fn, cl->parent,
169 			   r & CLOSURE_REMAINING_MASK);
170 
171 		seq_printf(f, "%s%s%s%s\n",
172 			   test_bit(WORK_STRUCT_PENDING_BIT,
173 				    work_data_bits(&cl->work)) ? "Q" : "",
174 			   r & CLOSURE_RUNNING	? "R" : "",
175 			   r & CLOSURE_STACK	? "S" : "",
176 			   r & CLOSURE_SLEEPING	? "Sl" : "");
177 
178 		if (r & CLOSURE_WAITING)
179 			seq_printf(f, " W %pF\n",
180 				   (void *) cl->waiting_on);
181 
182 		seq_printf(f, "\n");
183 	}
184 
185 	spin_unlock_irq(&closure_list_lock);
186 	return 0;
187 }
188 
189 static int debug_seq_open(struct inode *inode, struct file *file)
190 {
191 	return single_open(file, debug_seq_show, NULL);
192 }
193 
194 static const struct file_operations debug_ops = {
195 	.owner		= THIS_MODULE,
196 	.open		= debug_seq_open,
197 	.read		= seq_read,
198 	.release	= single_release
199 };
200 
201 void __init closure_debug_init(void)
202 {
203 	debug = debugfs_create_file("closures", 0400, NULL, NULL, &debug_ops);
204 }
205 
206 #endif
207 
208 MODULE_AUTHOR("Kent Overstreet <koverstreet@google.com>");
209 MODULE_LICENSE("GPL");
210