tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
14static 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 */
46void closure_sub(struct closure *cl, int v)
47{
48 closure_put_after_sub(cl, atomic_sub_return(v, &cl->remaining));
49}
50EXPORT_SYMBOL(closure_sub);
51
52/**
53 * closure_put - decrement a closure's refcount
54 */
55void closure_put(struct closure *cl)
56{
57 closure_put_after_sub(cl, atomic_dec_return(&cl->remaining));
58}
59EXPORT_SYMBOL(closure_put);
60
61/**
62 * closure_wake_up - wake up all closures on a wait list, without memory barrier
63 */
64void __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}
81EXPORT_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 */
90bool 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}
101EXPORT_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 */
109void 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}
124EXPORT_SYMBOL(closure_sync);
125
126#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
127
128static LIST_HEAD(closure_list);
129static DEFINE_SPINLOCK(closure_list_lock);
130
131void 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}
142EXPORT_SYMBOL(closure_debug_create);
143
144void 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}
155EXPORT_SYMBOL(closure_debug_destroy);
156
157static struct dentry *debug;
158
159static 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
189static int debug_seq_open(struct inode *inode, struct file *file)
190{
191 return single_open(file, debug_seq_show, NULL);
192}
193
194static 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
201void __init closure_debug_init(void)
202{
203 debug = debugfs_create_file("closures", 0400, NULL, NULL, &debug_ops);
204}
205
206#endif
207
208MODULE_AUTHOR("Kent Overstreet <koverstreet@google.com>");
209MODULE_LICENSE("GPL");