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1da177e4 LT |
1 | /* |
2 | * Generic waiting primitives. | |
3 | * | |
4 | * (C) 2004 William Irwin, Oracle | |
5 | */ | |
1da177e4 LT |
6 | #include <linux/init.h> |
7 | #include <linux/module.h> | |
8 | #include <linux/sched.h> | |
9 | #include <linux/mm.h> | |
10 | #include <linux/wait.h> | |
11 | #include <linux/hash.h> | |
12 | ||
21d71f51 IM |
13 | void init_waitqueue_head(wait_queue_head_t *q) |
14 | { | |
15 | spin_lock_init(&q->lock); | |
16 | INIT_LIST_HEAD(&q->task_list); | |
17 | } | |
eb4542b9 | 18 | |
21d71f51 | 19 | EXPORT_SYMBOL(init_waitqueue_head); |
eb4542b9 | 20 | |
1da177e4 LT |
21 | void fastcall add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait) |
22 | { | |
23 | unsigned long flags; | |
24 | ||
25 | wait->flags &= ~WQ_FLAG_EXCLUSIVE; | |
26 | spin_lock_irqsave(&q->lock, flags); | |
27 | __add_wait_queue(q, wait); | |
28 | spin_unlock_irqrestore(&q->lock, flags); | |
29 | } | |
30 | EXPORT_SYMBOL(add_wait_queue); | |
31 | ||
32 | void fastcall add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait) | |
33 | { | |
34 | unsigned long flags; | |
35 | ||
36 | wait->flags |= WQ_FLAG_EXCLUSIVE; | |
37 | spin_lock_irqsave(&q->lock, flags); | |
38 | __add_wait_queue_tail(q, wait); | |
39 | spin_unlock_irqrestore(&q->lock, flags); | |
40 | } | |
41 | EXPORT_SYMBOL(add_wait_queue_exclusive); | |
42 | ||
43 | void fastcall remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait) | |
44 | { | |
45 | unsigned long flags; | |
46 | ||
47 | spin_lock_irqsave(&q->lock, flags); | |
48 | __remove_wait_queue(q, wait); | |
49 | spin_unlock_irqrestore(&q->lock, flags); | |
50 | } | |
51 | EXPORT_SYMBOL(remove_wait_queue); | |
52 | ||
53 | ||
54 | /* | |
55 | * Note: we use "set_current_state()" _after_ the wait-queue add, | |
56 | * because we need a memory barrier there on SMP, so that any | |
57 | * wake-function that tests for the wait-queue being active | |
58 | * will be guaranteed to see waitqueue addition _or_ subsequent | |
59 | * tests in this thread will see the wakeup having taken place. | |
60 | * | |
61 | * The spin_unlock() itself is semi-permeable and only protects | |
62 | * one way (it only protects stuff inside the critical region and | |
63 | * stops them from bleeding out - it would still allow subsequent | |
59c51591 | 64 | * loads to move into the critical region). |
1da177e4 LT |
65 | */ |
66 | void fastcall | |
67 | prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state) | |
68 | { | |
69 | unsigned long flags; | |
70 | ||
71 | wait->flags &= ~WQ_FLAG_EXCLUSIVE; | |
72 | spin_lock_irqsave(&q->lock, flags); | |
73 | if (list_empty(&wait->task_list)) | |
74 | __add_wait_queue(q, wait); | |
75 | /* | |
76 | * don't alter the task state if this is just going to | |
77 | * queue an async wait queue callback | |
78 | */ | |
79 | if (is_sync_wait(wait)) | |
80 | set_current_state(state); | |
81 | spin_unlock_irqrestore(&q->lock, flags); | |
82 | } | |
83 | EXPORT_SYMBOL(prepare_to_wait); | |
84 | ||
85 | void fastcall | |
86 | prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state) | |
87 | { | |
88 | unsigned long flags; | |
89 | ||
90 | wait->flags |= WQ_FLAG_EXCLUSIVE; | |
91 | spin_lock_irqsave(&q->lock, flags); | |
92 | if (list_empty(&wait->task_list)) | |
93 | __add_wait_queue_tail(q, wait); | |
94 | /* | |
95 | * don't alter the task state if this is just going to | |
96 | * queue an async wait queue callback | |
97 | */ | |
98 | if (is_sync_wait(wait)) | |
99 | set_current_state(state); | |
100 | spin_unlock_irqrestore(&q->lock, flags); | |
101 | } | |
102 | EXPORT_SYMBOL(prepare_to_wait_exclusive); | |
103 | ||
104 | void fastcall finish_wait(wait_queue_head_t *q, wait_queue_t *wait) | |
105 | { | |
106 | unsigned long flags; | |
107 | ||
108 | __set_current_state(TASK_RUNNING); | |
109 | /* | |
110 | * We can check for list emptiness outside the lock | |
111 | * IFF: | |
112 | * - we use the "careful" check that verifies both | |
113 | * the next and prev pointers, so that there cannot | |
114 | * be any half-pending updates in progress on other | |
115 | * CPU's that we haven't seen yet (and that might | |
116 | * still change the stack area. | |
117 | * and | |
118 | * - all other users take the lock (ie we can only | |
119 | * have _one_ other CPU that looks at or modifies | |
120 | * the list). | |
121 | */ | |
122 | if (!list_empty_careful(&wait->task_list)) { | |
123 | spin_lock_irqsave(&q->lock, flags); | |
124 | list_del_init(&wait->task_list); | |
125 | spin_unlock_irqrestore(&q->lock, flags); | |
126 | } | |
127 | } | |
128 | EXPORT_SYMBOL(finish_wait); | |
129 | ||
130 | int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key) | |
131 | { | |
132 | int ret = default_wake_function(wait, mode, sync, key); | |
133 | ||
134 | if (ret) | |
135 | list_del_init(&wait->task_list); | |
136 | return ret; | |
137 | } | |
138 | EXPORT_SYMBOL(autoremove_wake_function); | |
139 | ||
140 | int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *arg) | |
141 | { | |
142 | struct wait_bit_key *key = arg; | |
143 | struct wait_bit_queue *wait_bit | |
144 | = container_of(wait, struct wait_bit_queue, wait); | |
145 | ||
146 | if (wait_bit->key.flags != key->flags || | |
147 | wait_bit->key.bit_nr != key->bit_nr || | |
148 | test_bit(key->bit_nr, key->flags)) | |
149 | return 0; | |
150 | else | |
151 | return autoremove_wake_function(wait, mode, sync, key); | |
152 | } | |
153 | EXPORT_SYMBOL(wake_bit_function); | |
154 | ||
155 | /* | |
156 | * To allow interruptible waiting and asynchronous (i.e. nonblocking) | |
157 | * waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are | |
158 | * permitted return codes. Nonzero return codes halt waiting and return. | |
159 | */ | |
160 | int __sched fastcall | |
161 | __wait_on_bit(wait_queue_head_t *wq, struct wait_bit_queue *q, | |
162 | int (*action)(void *), unsigned mode) | |
163 | { | |
164 | int ret = 0; | |
165 | ||
166 | do { | |
167 | prepare_to_wait(wq, &q->wait, mode); | |
168 | if (test_bit(q->key.bit_nr, q->key.flags)) | |
169 | ret = (*action)(q->key.flags); | |
170 | } while (test_bit(q->key.bit_nr, q->key.flags) && !ret); | |
171 | finish_wait(wq, &q->wait); | |
172 | return ret; | |
173 | } | |
174 | EXPORT_SYMBOL(__wait_on_bit); | |
175 | ||
176 | int __sched fastcall out_of_line_wait_on_bit(void *word, int bit, | |
177 | int (*action)(void *), unsigned mode) | |
178 | { | |
179 | wait_queue_head_t *wq = bit_waitqueue(word, bit); | |
180 | DEFINE_WAIT_BIT(wait, word, bit); | |
181 | ||
182 | return __wait_on_bit(wq, &wait, action, mode); | |
183 | } | |
184 | EXPORT_SYMBOL(out_of_line_wait_on_bit); | |
185 | ||
186 | int __sched fastcall | |
187 | __wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q, | |
188 | int (*action)(void *), unsigned mode) | |
189 | { | |
190 | int ret = 0; | |
191 | ||
192 | do { | |
193 | prepare_to_wait_exclusive(wq, &q->wait, mode); | |
194 | if (test_bit(q->key.bit_nr, q->key.flags)) { | |
195 | if ((ret = (*action)(q->key.flags))) | |
196 | break; | |
197 | } | |
198 | } while (test_and_set_bit(q->key.bit_nr, q->key.flags)); | |
199 | finish_wait(wq, &q->wait); | |
200 | return ret; | |
201 | } | |
202 | EXPORT_SYMBOL(__wait_on_bit_lock); | |
203 | ||
204 | int __sched fastcall out_of_line_wait_on_bit_lock(void *word, int bit, | |
205 | int (*action)(void *), unsigned mode) | |
206 | { | |
207 | wait_queue_head_t *wq = bit_waitqueue(word, bit); | |
208 | DEFINE_WAIT_BIT(wait, word, bit); | |
209 | ||
210 | return __wait_on_bit_lock(wq, &wait, action, mode); | |
211 | } | |
212 | EXPORT_SYMBOL(out_of_line_wait_on_bit_lock); | |
213 | ||
214 | void fastcall __wake_up_bit(wait_queue_head_t *wq, void *word, int bit) | |
215 | { | |
216 | struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit); | |
217 | if (waitqueue_active(wq)) | |
e64d66c8 | 218 | __wake_up(wq, TASK_NORMAL, 1, &key); |
1da177e4 LT |
219 | } |
220 | EXPORT_SYMBOL(__wake_up_bit); | |
221 | ||
222 | /** | |
223 | * wake_up_bit - wake up a waiter on a bit | |
224 | * @word: the word being waited on, a kernel virtual address | |
225 | * @bit: the bit of the word being waited on | |
226 | * | |
227 | * There is a standard hashed waitqueue table for generic use. This | |
228 | * is the part of the hashtable's accessor API that wakes up waiters | |
229 | * on a bit. For instance, if one were to have waiters on a bitflag, | |
230 | * one would call wake_up_bit() after clearing the bit. | |
231 | * | |
232 | * In order for this to function properly, as it uses waitqueue_active() | |
233 | * internally, some kind of memory barrier must be done prior to calling | |
234 | * this. Typically, this will be smp_mb__after_clear_bit(), but in some | |
235 | * cases where bitflags are manipulated non-atomically under a lock, one | |
236 | * may need to use a less regular barrier, such fs/inode.c's smp_mb(), | |
237 | * because spin_unlock() does not guarantee a memory barrier. | |
238 | */ | |
239 | void fastcall wake_up_bit(void *word, int bit) | |
240 | { | |
241 | __wake_up_bit(bit_waitqueue(word, bit), word, bit); | |
242 | } | |
243 | EXPORT_SYMBOL(wake_up_bit); | |
244 | ||
245 | fastcall wait_queue_head_t *bit_waitqueue(void *word, int bit) | |
246 | { | |
247 | const int shift = BITS_PER_LONG == 32 ? 5 : 6; | |
248 | const struct zone *zone = page_zone(virt_to_page(word)); | |
249 | unsigned long val = (unsigned long)word << shift | bit; | |
250 | ||
251 | return &zone->wait_table[hash_long(val, zone->wait_table_bits)]; | |
252 | } | |
253 | EXPORT_SYMBOL(bit_waitqueue); |