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