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457c8996 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
5dd43ce2 IM |
2 | /* |
3 | * The implementation of the wait_bit*() and related waiting APIs: | |
4 | */ | |
325ea10c | 5 | #include "sched.h" |
5822a454 IM |
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 | wait_queue_head_t *bit_waitqueue(void *word, int bit) | |
13 | { | |
14 | const int shift = BITS_PER_LONG == 32 ? 5 : 6; | |
15 | unsigned long val = (unsigned long)word << shift | bit; | |
16 | ||
17 | return bit_wait_table + hash_long(val, WAIT_TABLE_BITS); | |
18 | } | |
19 | EXPORT_SYMBOL(bit_waitqueue); | |
5dd43ce2 IM |
20 | |
21 | int wake_bit_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *arg) | |
22 | { | |
23 | struct wait_bit_key *key = arg; | |
24 | struct wait_bit_queue_entry *wait_bit = container_of(wq_entry, struct wait_bit_queue_entry, wq_entry); | |
25 | ||
26 | if (wait_bit->key.flags != key->flags || | |
27 | wait_bit->key.bit_nr != key->bit_nr || | |
28 | test_bit(key->bit_nr, key->flags)) | |
29 | return 0; | |
97fb7a0a IM |
30 | |
31 | return autoremove_wake_function(wq_entry, mode, sync, key); | |
5dd43ce2 IM |
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 | __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 | int ret = 0; | |
45 | ||
46 | do { | |
47 | prepare_to_wait(wq_head, &wbq_entry->wq_entry, mode); | |
48 | if (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags)) | |
49 | ret = (*action)(&wbq_entry->key, mode); | |
50 | } while (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags) && !ret); | |
97fb7a0a | 51 | |
5dd43ce2 | 52 | finish_wait(wq_head, &wbq_entry->wq_entry); |
97fb7a0a | 53 | |
5dd43ce2 IM |
54 | return ret; |
55 | } | |
56 | EXPORT_SYMBOL(__wait_on_bit); | |
57 | ||
58 | int __sched out_of_line_wait_on_bit(void *word, int bit, | |
59 | wait_bit_action_f *action, unsigned mode) | |
60 | { | |
61 | struct wait_queue_head *wq_head = bit_waitqueue(word, bit); | |
62 | DEFINE_WAIT_BIT(wq_entry, word, bit); | |
63 | ||
64 | return __wait_on_bit(wq_head, &wq_entry, action, mode); | |
65 | } | |
66 | EXPORT_SYMBOL(out_of_line_wait_on_bit); | |
67 | ||
68 | 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 | struct wait_queue_head *wq_head = bit_waitqueue(word, bit); | |
73 | DEFINE_WAIT_BIT(wq_entry, word, bit); | |
74 | ||
75 | wq_entry.key.timeout = jiffies + timeout; | |
97fb7a0a | 76 | |
5dd43ce2 IM |
77 | 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 | __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 | int ret = 0; | |
86 | ||
87 | for (;;) { | |
88 | prepare_to_wait_exclusive(wq_head, &wbq_entry->wq_entry, mode); | |
89 | if (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags)) { | |
90 | 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 | if (ret) | |
98 | finish_wait(wq_head, &wbq_entry->wq_entry); | |
99 | } | |
100 | if (!test_and_set_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags)) { | |
101 | if (!ret) | |
102 | finish_wait(wq_head, &wbq_entry->wq_entry); | |
103 | return 0; | |
104 | } else if (ret) { | |
105 | return ret; | |
106 | } | |
107 | } | |
108 | } | |
109 | EXPORT_SYMBOL(__wait_on_bit_lock); | |
110 | ||
111 | int __sched out_of_line_wait_on_bit_lock(void *word, int bit, | |
112 | wait_bit_action_f *action, unsigned mode) | |
113 | { | |
114 | struct wait_queue_head *wq_head = bit_waitqueue(word, bit); | |
115 | DEFINE_WAIT_BIT(wq_entry, word, bit); | |
116 | ||
117 | return __wait_on_bit_lock(wq_head, &wq_entry, action, mode); | |
118 | } | |
119 | EXPORT_SYMBOL(out_of_line_wait_on_bit_lock); | |
120 | ||
121 | void __wake_up_bit(struct wait_queue_head *wq_head, void *word, int bit) | |
122 | { | |
123 | struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit); | |
97fb7a0a | 124 | |
5dd43ce2 IM |
125 | if (waitqueue_active(wq_head)) |
126 | __wake_up(wq_head, TASK_NORMAL, 1, &key); | |
127 | } | |
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 | void wake_up_bit(void *word, int bit) | |
148 | { | |
149 | __wake_up_bit(bit_waitqueue(word, bit), word, bit); | |
150 | } | |
151 | EXPORT_SYMBOL(wake_up_bit); | |
152 | ||
6b2bb726 PZ |
153 | wait_queue_head_t *__var_waitqueue(void *p) |
154 | { | |
b3fc5c9b | 155 | return bit_wait_table + hash_ptr(p, WAIT_TABLE_BITS); |
6b2bb726 PZ |
156 | } |
157 | EXPORT_SYMBOL(__var_waitqueue); | |
158 | ||
159 | static int | |
160 | var_wake_function(struct wait_queue_entry *wq_entry, unsigned int mode, | |
161 | int sync, void *arg) | |
162 | { | |
163 | struct wait_bit_key *key = arg; | |
164 | struct wait_bit_queue_entry *wbq_entry = | |
165 | container_of(wq_entry, struct wait_bit_queue_entry, wq_entry); | |
166 | ||
167 | if (wbq_entry->key.flags != key->flags || | |
168 | 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 | void init_wait_var_entry(struct wait_bit_queue_entry *wbq_entry, void *var, int flags) | |
175 | { | |
176 | *wbq_entry = (struct wait_bit_queue_entry){ | |
177 | .key = { | |
178 | .flags = (var), | |
179 | .bit_nr = -1, | |
180 | }, | |
181 | .wq_entry = { | |
182 | .private = current, | |
183 | .func = var_wake_function, | |
184 | .entry = LIST_HEAD_INIT(wbq_entry->wq_entry.entry), | |
185 | }, | |
186 | }; | |
187 | } | |
188 | EXPORT_SYMBOL(init_wait_var_entry); | |
189 | ||
190 | void wake_up_var(void *var) | |
191 | { | |
192 | __wake_up_bit(__var_waitqueue(var), var, -1); | |
193 | } | |
194 | EXPORT_SYMBOL(wake_up_var); | |
195 | ||
5dd43ce2 IM |
196 | __sched int bit_wait(struct wait_bit_key *word, int mode) |
197 | { | |
198 | schedule(); | |
199 | if (signal_pending_state(mode, current)) | |
200 | return -EINTR; | |
97fb7a0a | 201 | |
5dd43ce2 IM |
202 | return 0; |
203 | } | |
204 | EXPORT_SYMBOL(bit_wait); | |
205 | ||
206 | __sched int bit_wait_io(struct wait_bit_key *word, int mode) | |
207 | { | |
208 | io_schedule(); | |
209 | if (signal_pending_state(mode, current)) | |
210 | return -EINTR; | |
97fb7a0a | 211 | |
5dd43ce2 IM |
212 | return 0; |
213 | } | |
214 | EXPORT_SYMBOL(bit_wait_io); | |
215 | ||
216 | __sched int bit_wait_timeout(struct wait_bit_key *word, int mode) | |
217 | { | |
218 | unsigned long now = READ_ONCE(jiffies); | |
97fb7a0a | 219 | |
5dd43ce2 IM |
220 | if (time_after_eq(now, word->timeout)) |
221 | return -EAGAIN; | |
222 | schedule_timeout(word->timeout - now); | |
223 | if (signal_pending_state(mode, current)) | |
224 | return -EINTR; | |
97fb7a0a | 225 | |
5dd43ce2 IM |
226 | return 0; |
227 | } | |
228 | EXPORT_SYMBOL_GPL(bit_wait_timeout); | |
229 | ||
230 | __sched int bit_wait_io_timeout(struct wait_bit_key *word, int mode) | |
231 | { | |
232 | unsigned long now = READ_ONCE(jiffies); | |
97fb7a0a | 233 | |
5dd43ce2 IM |
234 | if (time_after_eq(now, word->timeout)) |
235 | return -EAGAIN; | |
236 | io_schedule_timeout(word->timeout - now); | |
237 | if (signal_pending_state(mode, current)) | |
238 | return -EINTR; | |
97fb7a0a | 239 | |
5dd43ce2 IM |
240 | return 0; |
241 | } | |
242 | EXPORT_SYMBOL_GPL(bit_wait_io_timeout); | |
5822a454 IM |
243 | |
244 | void __init wait_bit_init(void) | |
245 | { | |
246 | int i; | |
247 | ||
248 | for (i = 0; i < WAIT_TABLE_SIZE; i++) | |
249 | init_waitqueue_head(bit_wait_table + i); | |
250 | } |