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