Line data Source code
1 : // SPDX-License-Identifier: GPL-2.0-only
2 :
3 : /*
4 : * The implementation of the wait_bit*() and related waiting APIs:
5 : */
6 :
7 : #define WAIT_TABLE_BITS 8
8 : #define WAIT_TABLE_SIZE (1 << WAIT_TABLE_BITS)
9 :
10 : static wait_queue_head_t bit_wait_table[WAIT_TABLE_SIZE] __cacheline_aligned;
11 :
12 44 : wait_queue_head_t *bit_waitqueue(void *word, int bit)
13 : {
14 88 : const int shift = BITS_PER_LONG == 32 ? 5 : 6;
15 88 : unsigned long val = (unsigned long)word << shift | bit;
16 :
17 88 : return bit_wait_table + hash_long(val, WAIT_TABLE_BITS);
18 : }
19 : EXPORT_SYMBOL(bit_waitqueue);
20 :
21 0 : int wake_bit_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *arg)
22 : {
23 0 : struct wait_bit_key *key = arg;
24 0 : struct wait_bit_queue_entry *wait_bit = container_of(wq_entry, struct wait_bit_queue_entry, wq_entry);
25 :
26 0 : if (wait_bit->key.flags != key->flags ||
27 0 : wait_bit->key.bit_nr != key->bit_nr ||
28 0 : test_bit(key->bit_nr, key->flags))
29 : return 0;
30 :
31 : return autoremove_wake_function(wq_entry, mode, sync, key);
32 : }
33 : EXPORT_SYMBOL(wake_bit_function);
34 :
35 : /*
36 : * To allow interruptible waiting and asynchronous (i.e. nonblocking)
37 : * waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are
38 : * permitted return codes. Nonzero return codes halt waiting and return.
39 : */
40 : int __sched
41 0 : __wait_on_bit(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry,
42 : wait_bit_action_f *action, unsigned mode)
43 : {
44 0 : int ret = 0;
45 :
46 : do {
47 0 : prepare_to_wait(wq_head, &wbq_entry->wq_entry, mode);
48 0 : if (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags))
49 0 : ret = (*action)(&wbq_entry->key, mode);
50 0 : } while (test_bit_acquire(wbq_entry->key.bit_nr, wbq_entry->key.flags) && !ret);
51 :
52 0 : finish_wait(wq_head, &wbq_entry->wq_entry);
53 :
54 0 : return ret;
55 : }
56 : EXPORT_SYMBOL(__wait_on_bit);
57 :
58 0 : int __sched out_of_line_wait_on_bit(void *word, int bit,
59 : wait_bit_action_f *action, unsigned mode)
60 : {
61 0 : struct wait_queue_head *wq_head = bit_waitqueue(word, bit);
62 0 : DEFINE_WAIT_BIT(wq_entry, word, bit);
63 :
64 0 : return __wait_on_bit(wq_head, &wq_entry, action, mode);
65 : }
66 : EXPORT_SYMBOL(out_of_line_wait_on_bit);
67 :
68 0 : int __sched out_of_line_wait_on_bit_timeout(
69 : void *word, int bit, wait_bit_action_f *action,
70 : unsigned mode, unsigned long timeout)
71 : {
72 0 : struct wait_queue_head *wq_head = bit_waitqueue(word, bit);
73 0 : DEFINE_WAIT_BIT(wq_entry, word, bit);
74 :
75 0 : wq_entry.key.timeout = jiffies + timeout;
76 :
77 0 : return __wait_on_bit(wq_head, &wq_entry, action, mode);
78 : }
79 : EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout);
80 :
81 : int __sched
82 0 : __wait_on_bit_lock(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry,
83 : wait_bit_action_f *action, unsigned mode)
84 : {
85 0 : int ret = 0;
86 :
87 : for (;;) {
88 0 : prepare_to_wait_exclusive(wq_head, &wbq_entry->wq_entry, mode);
89 0 : if (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags)) {
90 0 : ret = action(&wbq_entry->key, mode);
91 : /*
92 : * See the comment in prepare_to_wait_event().
93 : * finish_wait() does not necessarily takes wwq_head->lock,
94 : * but test_and_set_bit() implies mb() which pairs with
95 : * smp_mb__after_atomic() before wake_up_page().
96 : */
97 0 : if (ret)
98 0 : finish_wait(wq_head, &wbq_entry->wq_entry);
99 : }
100 0 : if (!test_and_set_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags)) {
101 0 : if (!ret)
102 0 : finish_wait(wq_head, &wbq_entry->wq_entry);
103 : return 0;
104 0 : } else if (ret) {
105 : return ret;
106 : }
107 : }
108 : }
109 : EXPORT_SYMBOL(__wait_on_bit_lock);
110 :
111 0 : int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
112 : wait_bit_action_f *action, unsigned mode)
113 : {
114 0 : struct wait_queue_head *wq_head = bit_waitqueue(word, bit);
115 0 : DEFINE_WAIT_BIT(wq_entry, word, bit);
116 :
117 0 : return __wait_on_bit_lock(wq_head, &wq_entry, action, mode);
118 : }
119 : EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
120 :
121 44 : void __wake_up_bit(struct wait_queue_head *wq_head, void *word, int bit)
122 : {
123 44 : struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
124 :
125 44 : if (waitqueue_active(wq_head))
126 : __wake_up(wq_head, TASK_NORMAL, 1, &key);
127 44 : }
128 : EXPORT_SYMBOL(__wake_up_bit);
129 :
130 : /**
131 : * wake_up_bit - wake up a waiter on a bit
132 : * @word: the word being waited on, a kernel virtual address
133 : * @bit: the bit of the word being waited on
134 : *
135 : * There is a standard hashed waitqueue table for generic use. This
136 : * is the part of the hashtable's accessor API that wakes up waiters
137 : * on a bit. For instance, if one were to have waiters on a bitflag,
138 : * one would call wake_up_bit() after clearing the bit.
139 : *
140 : * In order for this to function properly, as it uses waitqueue_active()
141 : * internally, some kind of memory barrier must be done prior to calling
142 : * this. Typically, this will be smp_mb__after_atomic(), but in some
143 : * cases where bitflags are manipulated non-atomically under a lock, one
144 : * may need to use a less regular barrier, such fs/inode.c's smp_mb(),
145 : * because spin_unlock() does not guarantee a memory barrier.
146 : */
147 44 : void wake_up_bit(void *word, int bit)
148 : {
149 44 : __wake_up_bit(bit_waitqueue(word, bit), word, bit);
150 44 : }
151 : EXPORT_SYMBOL(wake_up_bit);
152 :
153 0 : wait_queue_head_t *__var_waitqueue(void *p)
154 : {
155 0 : return bit_wait_table + hash_ptr(p, WAIT_TABLE_BITS);
156 : }
157 : EXPORT_SYMBOL(__var_waitqueue);
158 :
159 : static int
160 0 : var_wake_function(struct wait_queue_entry *wq_entry, unsigned int mode,
161 : int sync, void *arg)
162 : {
163 0 : struct wait_bit_key *key = arg;
164 0 : struct wait_bit_queue_entry *wbq_entry =
165 0 : container_of(wq_entry, struct wait_bit_queue_entry, wq_entry);
166 :
167 0 : if (wbq_entry->key.flags != key->flags ||
168 0 : wbq_entry->key.bit_nr != key->bit_nr)
169 : return 0;
170 :
171 : return autoremove_wake_function(wq_entry, mode, sync, key);
172 : }
173 :
174 0 : void init_wait_var_entry(struct wait_bit_queue_entry *wbq_entry, void *var, int flags)
175 : {
176 0 : *wbq_entry = (struct wait_bit_queue_entry){
177 : .key = {
178 : .flags = (var),
179 : .bit_nr = -1,
180 : },
181 : .wq_entry = {
182 : .flags = flags,
183 0 : .private = current,
184 : .func = var_wake_function,
185 0 : .entry = LIST_HEAD_INIT(wbq_entry->wq_entry.entry),
186 : },
187 : };
188 0 : }
189 : EXPORT_SYMBOL(init_wait_var_entry);
190 :
191 0 : void wake_up_var(void *var)
192 : {
193 0 : __wake_up_bit(__var_waitqueue(var), var, -1);
194 0 : }
195 : EXPORT_SYMBOL(wake_up_var);
196 :
197 0 : __sched int bit_wait(struct wait_bit_key *word, int mode)
198 : {
199 0 : schedule();
200 0 : if (signal_pending_state(mode, current))
201 : return -EINTR;
202 :
203 0 : return 0;
204 : }
205 : EXPORT_SYMBOL(bit_wait);
206 :
207 0 : __sched int bit_wait_io(struct wait_bit_key *word, int mode)
208 : {
209 0 : io_schedule();
210 0 : if (signal_pending_state(mode, current))
211 : return -EINTR;
212 :
213 0 : return 0;
214 : }
215 : EXPORT_SYMBOL(bit_wait_io);
216 :
217 0 : __sched int bit_wait_timeout(struct wait_bit_key *word, int mode)
218 : {
219 0 : unsigned long now = READ_ONCE(jiffies);
220 :
221 0 : if (time_after_eq(now, word->timeout))
222 : return -EAGAIN;
223 0 : schedule_timeout(word->timeout - now);
224 0 : if (signal_pending_state(mode, current))
225 : return -EINTR;
226 :
227 0 : return 0;
228 : }
229 : EXPORT_SYMBOL_GPL(bit_wait_timeout);
230 :
231 0 : __sched int bit_wait_io_timeout(struct wait_bit_key *word, int mode)
232 : {
233 0 : unsigned long now = READ_ONCE(jiffies);
234 :
235 0 : if (time_after_eq(now, word->timeout))
236 : return -EAGAIN;
237 0 : io_schedule_timeout(word->timeout - now);
238 0 : if (signal_pending_state(mode, current))
239 : return -EINTR;
240 :
241 0 : return 0;
242 : }
243 : EXPORT_SYMBOL_GPL(bit_wait_io_timeout);
244 :
245 1 : void __init wait_bit_init(void)
246 : {
247 : int i;
248 :
249 257 : for (i = 0; i < WAIT_TABLE_SIZE; i++)
250 512 : init_waitqueue_head(bit_wait_table + i);
251 1 : }
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