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5dd43ce2 IM |
1 | /* |
2 | * The implementation of the wait_bit*() and related waiting APIs: | |
3 | */ | |
4 | #include <linux/wait_bit.h> | |
5 | #include <linux/sched/signal.h> | |
6 | #include <linux/sched/debug.h> | |
5822a454 IM |
7 | #include <linux/hash.h> |
8 | ||
9 | #define WAIT_TABLE_BITS 8 | |
10 | #define WAIT_TABLE_SIZE (1 << WAIT_TABLE_BITS) | |
11 | ||
12 | static wait_queue_head_t bit_wait_table[WAIT_TABLE_SIZE] __cacheline_aligned; | |
13 | ||
14 | wait_queue_head_t *bit_waitqueue(void *word, int bit) | |
15 | { | |
16 | const int shift = BITS_PER_LONG == 32 ? 5 : 6; | |
17 | unsigned long val = (unsigned long)word << shift | bit; | |
18 | ||
19 | return bit_wait_table + hash_long(val, WAIT_TABLE_BITS); | |
20 | } | |
21 | EXPORT_SYMBOL(bit_waitqueue); | |
5dd43ce2 IM |
22 | |
23 | int wake_bit_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *arg) | |
24 | { | |
25 | struct wait_bit_key *key = arg; | |
26 | struct wait_bit_queue_entry *wait_bit = container_of(wq_entry, struct wait_bit_queue_entry, wq_entry); | |
27 | ||
28 | if (wait_bit->key.flags != key->flags || | |
29 | wait_bit->key.bit_nr != key->bit_nr || | |
30 | test_bit(key->bit_nr, key->flags)) | |
31 | return 0; | |
32 | else | |
33 | return autoremove_wake_function(wq_entry, mode, sync, key); | |
34 | } | |
35 | EXPORT_SYMBOL(wake_bit_function); | |
36 | ||
37 | /* | |
38 | * To allow interruptible waiting and asynchronous (i.e. nonblocking) | |
39 | * waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are | |
40 | * permitted return codes. Nonzero return codes halt waiting and return. | |
41 | */ | |
42 | int __sched | |
43 | __wait_on_bit(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry, | |
44 | wait_bit_action_f *action, unsigned mode) | |
45 | { | |
46 | int ret = 0; | |
47 | ||
48 | do { | |
49 | prepare_to_wait(wq_head, &wbq_entry->wq_entry, mode); | |
50 | if (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags)) | |
51 | ret = (*action)(&wbq_entry->key, mode); | |
52 | } while (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags) && !ret); | |
53 | finish_wait(wq_head, &wbq_entry->wq_entry); | |
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; | |
76 | return __wait_on_bit(wq_head, &wq_entry, action, mode); | |
77 | } | |
78 | EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout); | |
79 | ||
80 | int __sched | |
81 | __wait_on_bit_lock(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry, | |
82 | wait_bit_action_f *action, unsigned mode) | |
83 | { | |
84 | int ret = 0; | |
85 | ||
86 | for (;;) { | |
87 | prepare_to_wait_exclusive(wq_head, &wbq_entry->wq_entry, mode); | |
88 | if (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags)) { | |
89 | ret = action(&wbq_entry->key, mode); | |
90 | /* | |
91 | * See the comment in prepare_to_wait_event(). | |
92 | * finish_wait() does not necessarily takes wwq_head->lock, | |
93 | * but test_and_set_bit() implies mb() which pairs with | |
94 | * smp_mb__after_atomic() before wake_up_page(). | |
95 | */ | |
96 | if (ret) | |
97 | finish_wait(wq_head, &wbq_entry->wq_entry); | |
98 | } | |
99 | if (!test_and_set_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags)) { | |
100 | if (!ret) | |
101 | finish_wait(wq_head, &wbq_entry->wq_entry); | |
102 | return 0; | |
103 | } else if (ret) { | |
104 | return ret; | |
105 | } | |
106 | } | |
107 | } | |
108 | EXPORT_SYMBOL(__wait_on_bit_lock); | |
109 | ||
110 | int __sched out_of_line_wait_on_bit_lock(void *word, int bit, | |
111 | wait_bit_action_f *action, unsigned mode) | |
112 | { | |
113 | struct wait_queue_head *wq_head = bit_waitqueue(word, bit); | |
114 | DEFINE_WAIT_BIT(wq_entry, word, bit); | |
115 | ||
116 | return __wait_on_bit_lock(wq_head, &wq_entry, action, mode); | |
117 | } | |
118 | EXPORT_SYMBOL(out_of_line_wait_on_bit_lock); | |
119 | ||
120 | void __wake_up_bit(struct wait_queue_head *wq_head, void *word, int bit) | |
121 | { | |
122 | struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit); | |
123 | if (waitqueue_active(wq_head)) | |
124 | __wake_up(wq_head, TASK_NORMAL, 1, &key); | |
125 | } | |
126 | EXPORT_SYMBOL(__wake_up_bit); | |
127 | ||
128 | /** | |
129 | * wake_up_bit - wake up a waiter on a bit | |
130 | * @word: the word being waited on, a kernel virtual address | |
131 | * @bit: the bit of the word being waited on | |
132 | * | |
133 | * There is a standard hashed waitqueue table for generic use. This | |
134 | * is the part of the hashtable's accessor API that wakes up waiters | |
135 | * on a bit. For instance, if one were to have waiters on a bitflag, | |
136 | * one would call wake_up_bit() after clearing the bit. | |
137 | * | |
138 | * In order for this to function properly, as it uses waitqueue_active() | |
139 | * internally, some kind of memory barrier must be done prior to calling | |
140 | * this. Typically, this will be smp_mb__after_atomic(), but in some | |
141 | * cases where bitflags are manipulated non-atomically under a lock, one | |
142 | * may need to use a less regular barrier, such fs/inode.c's smp_mb(), | |
143 | * because spin_unlock() does not guarantee a memory barrier. | |
144 | */ | |
145 | void wake_up_bit(void *word, int bit) | |
146 | { | |
147 | __wake_up_bit(bit_waitqueue(word, bit), word, bit); | |
148 | } | |
149 | EXPORT_SYMBOL(wake_up_bit); | |
150 | ||
151 | /* | |
152 | * Manipulate the atomic_t address to produce a better bit waitqueue table hash | |
153 | * index (we're keying off bit -1, but that would produce a horrible hash | |
154 | * value). | |
155 | */ | |
156 | static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p) | |
157 | { | |
158 | if (BITS_PER_LONG == 64) { | |
159 | unsigned long q = (unsigned long)p; | |
160 | return bit_waitqueue((void *)(q & ~1), q & 1); | |
161 | } | |
162 | return bit_waitqueue(p, 0); | |
163 | } | |
164 | ||
165 | static int wake_atomic_t_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, | |
166 | void *arg) | |
167 | { | |
168 | struct wait_bit_key *key = arg; | |
169 | struct wait_bit_queue_entry *wait_bit = container_of(wq_entry, struct wait_bit_queue_entry, wq_entry); | |
170 | atomic_t *val = key->flags; | |
171 | ||
172 | if (wait_bit->key.flags != key->flags || | |
173 | wait_bit->key.bit_nr != key->bit_nr || | |
174 | atomic_read(val) != 0) | |
175 | return 0; | |
176 | return autoremove_wake_function(wq_entry, mode, sync, key); | |
177 | } | |
178 | ||
179 | /* | |
180 | * To allow interruptible waiting and asynchronous (i.e. nonblocking) waiting, | |
181 | * the actions of __wait_on_atomic_t() are permitted return codes. Nonzero | |
182 | * return codes halt waiting and return. | |
183 | */ | |
184 | static __sched | |
185 | int __wait_on_atomic_t(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry, | |
5e4def20 | 186 | wait_atomic_t_action_f action, unsigned int mode) |
5dd43ce2 IM |
187 | { |
188 | atomic_t *val; | |
189 | int ret = 0; | |
190 | ||
191 | do { | |
192 | prepare_to_wait(wq_head, &wbq_entry->wq_entry, mode); | |
193 | val = wbq_entry->key.flags; | |
194 | if (atomic_read(val) == 0) | |
195 | break; | |
5e4def20 | 196 | ret = (*action)(val, mode); |
5dd43ce2 IM |
197 | } while (!ret && atomic_read(val) != 0); |
198 | finish_wait(wq_head, &wbq_entry->wq_entry); | |
199 | return ret; | |
200 | } | |
201 | ||
202 | #define DEFINE_WAIT_ATOMIC_T(name, p) \ | |
203 | struct wait_bit_queue_entry name = { \ | |
204 | .key = __WAIT_ATOMIC_T_KEY_INITIALIZER(p), \ | |
205 | .wq_entry = { \ | |
206 | .private = current, \ | |
207 | .func = wake_atomic_t_function, \ | |
2055da97 IM |
208 | .entry = \ |
209 | LIST_HEAD_INIT((name).wq_entry.entry), \ | |
5dd43ce2 IM |
210 | }, \ |
211 | } | |
212 | ||
5e4def20 DH |
213 | __sched int out_of_line_wait_on_atomic_t(atomic_t *p, |
214 | wait_atomic_t_action_f action, | |
215 | unsigned int mode) | |
5dd43ce2 IM |
216 | { |
217 | struct wait_queue_head *wq_head = atomic_t_waitqueue(p); | |
218 | DEFINE_WAIT_ATOMIC_T(wq_entry, p); | |
219 | ||
220 | return __wait_on_atomic_t(wq_head, &wq_entry, action, mode); | |
221 | } | |
222 | EXPORT_SYMBOL(out_of_line_wait_on_atomic_t); | |
223 | ||
5e4def20 DH |
224 | __sched int atomic_t_wait(atomic_t *counter, unsigned int mode) |
225 | { | |
226 | schedule(); | |
227 | if (signal_pending_state(mode, current)) | |
228 | return -EINTR; | |
229 | return 0; | |
230 | } | |
231 | EXPORT_SYMBOL(atomic_t_wait); | |
232 | ||
5dd43ce2 IM |
233 | /** |
234 | * wake_up_atomic_t - Wake up a waiter on a atomic_t | |
235 | * @p: The atomic_t being waited on, a kernel virtual address | |
236 | * | |
237 | * Wake up anyone waiting for the atomic_t to go to zero. | |
238 | * | |
239 | * Abuse the bit-waker function and its waitqueue hash table set (the atomic_t | |
240 | * check is done by the waiter's wake function, not the by the waker itself). | |
241 | */ | |
242 | void wake_up_atomic_t(atomic_t *p) | |
243 | { | |
244 | __wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR); | |
245 | } | |
246 | EXPORT_SYMBOL(wake_up_atomic_t); | |
247 | ||
248 | __sched int bit_wait(struct wait_bit_key *word, int mode) | |
249 | { | |
250 | schedule(); | |
251 | if (signal_pending_state(mode, current)) | |
252 | return -EINTR; | |
253 | return 0; | |
254 | } | |
255 | EXPORT_SYMBOL(bit_wait); | |
256 | ||
257 | __sched int bit_wait_io(struct wait_bit_key *word, int mode) | |
258 | { | |
259 | io_schedule(); | |
260 | if (signal_pending_state(mode, current)) | |
261 | return -EINTR; | |
262 | return 0; | |
263 | } | |
264 | EXPORT_SYMBOL(bit_wait_io); | |
265 | ||
266 | __sched int bit_wait_timeout(struct wait_bit_key *word, int mode) | |
267 | { | |
268 | unsigned long now = READ_ONCE(jiffies); | |
269 | if (time_after_eq(now, word->timeout)) | |
270 | return -EAGAIN; | |
271 | schedule_timeout(word->timeout - now); | |
272 | if (signal_pending_state(mode, current)) | |
273 | return -EINTR; | |
274 | return 0; | |
275 | } | |
276 | EXPORT_SYMBOL_GPL(bit_wait_timeout); | |
277 | ||
278 | __sched int bit_wait_io_timeout(struct wait_bit_key *word, int mode) | |
279 | { | |
280 | unsigned long now = READ_ONCE(jiffies); | |
281 | if (time_after_eq(now, word->timeout)) | |
282 | return -EAGAIN; | |
283 | io_schedule_timeout(word->timeout - now); | |
284 | if (signal_pending_state(mode, current)) | |
285 | return -EINTR; | |
286 | return 0; | |
287 | } | |
288 | EXPORT_SYMBOL_GPL(bit_wait_io_timeout); | |
5822a454 IM |
289 | |
290 | void __init wait_bit_init(void) | |
291 | { | |
292 | int i; | |
293 | ||
294 | for (i = 0; i < WAIT_TABLE_SIZE; i++) | |
295 | init_waitqueue_head(bit_wait_table + i); | |
296 | } |