1 // SPDX-License-Identifier: GPL-2.0-only
3 * The implementation of the wait_bit*() and related waiting APIs:
7 #define WAIT_TABLE_BITS 8
8 #define WAIT_TABLE_SIZE (1 << WAIT_TABLE_BITS)
10 static wait_queue_head_t bit_wait_table[WAIT_TABLE_SIZE] __cacheline_aligned;
12 wait_queue_head_t *bit_waitqueue(void *word, int bit)
14 const int shift = BITS_PER_LONG == 32 ? 5 : 6;
15 unsigned long val = (unsigned long)word << shift | bit;
17 return bit_wait_table + hash_long(val, WAIT_TABLE_BITS);
19 EXPORT_SYMBOL(bit_waitqueue);
21 int wake_bit_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *arg)
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);
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))
31 return autoremove_wake_function(wq_entry, mode, sync, key);
33 EXPORT_SYMBOL(wake_bit_function);
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.
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)
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);
52 finish_wait(wq_head, &wbq_entry->wq_entry);
56 EXPORT_SYMBOL(__wait_on_bit);
58 int __sched out_of_line_wait_on_bit(void *word, int bit,
59 wait_bit_action_f *action, unsigned mode)
61 struct wait_queue_head *wq_head = bit_waitqueue(word, bit);
62 DEFINE_WAIT_BIT(wq_entry, word, bit);
64 return __wait_on_bit(wq_head, &wq_entry, action, mode);
66 EXPORT_SYMBOL(out_of_line_wait_on_bit);
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)
72 struct wait_queue_head *wq_head = bit_waitqueue(word, bit);
73 DEFINE_WAIT_BIT(wq_entry, word, bit);
75 wq_entry.key.timeout = jiffies + timeout;
77 return __wait_on_bit(wq_head, &wq_entry, action, mode);
79 EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout);
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)
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);
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().
98 finish_wait(wq_head, &wbq_entry->wq_entry);
100 if (!test_and_set_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags)) {
102 finish_wait(wq_head, &wbq_entry->wq_entry);
109 EXPORT_SYMBOL(__wait_on_bit_lock);
111 int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
112 wait_bit_action_f *action, unsigned mode)
114 struct wait_queue_head *wq_head = bit_waitqueue(word, bit);
115 DEFINE_WAIT_BIT(wq_entry, word, bit);
117 return __wait_on_bit_lock(wq_head, &wq_entry, action, mode);
119 EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
121 void __wake_up_bit(struct wait_queue_head *wq_head, void *word, int bit)
123 struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
125 if (waitqueue_active(wq_head))
126 __wake_up(wq_head, TASK_NORMAL, 1, &key);
128 EXPORT_SYMBOL(__wake_up_bit);
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
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.
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.
147 void wake_up_bit(void *word, int bit)
149 __wake_up_bit(bit_waitqueue(word, bit), word, bit);
151 EXPORT_SYMBOL(wake_up_bit);
153 wait_queue_head_t *__var_waitqueue(void *p)
155 return bit_wait_table + hash_ptr(p, WAIT_TABLE_BITS);
157 EXPORT_SYMBOL(__var_waitqueue);
160 var_wake_function(struct wait_queue_entry *wq_entry, unsigned int mode,
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);
167 if (wbq_entry->key.flags != key->flags ||
168 wbq_entry->key.bit_nr != key->bit_nr)
171 return autoremove_wake_function(wq_entry, mode, sync, key);
174 void init_wait_var_entry(struct wait_bit_queue_entry *wbq_entry, void *var, int flags)
176 *wbq_entry = (struct wait_bit_queue_entry){
184 .func = var_wake_function,
185 .entry = LIST_HEAD_INIT(wbq_entry->wq_entry.entry),
189 EXPORT_SYMBOL(init_wait_var_entry);
191 void wake_up_var(void *var)
193 __wake_up_bit(__var_waitqueue(var), var, -1);
195 EXPORT_SYMBOL(wake_up_var);
197 __sched int bit_wait(struct wait_bit_key *word, int mode)
200 if (signal_pending_state(mode, current))
205 EXPORT_SYMBOL(bit_wait);
207 __sched int bit_wait_io(struct wait_bit_key *word, int mode)
210 if (signal_pending_state(mode, current))
215 EXPORT_SYMBOL(bit_wait_io);
217 __sched int bit_wait_timeout(struct wait_bit_key *word, int mode)
219 unsigned long now = READ_ONCE(jiffies);
221 if (time_after_eq(now, word->timeout))
223 schedule_timeout(word->timeout - now);
224 if (signal_pending_state(mode, current))
229 EXPORT_SYMBOL_GPL(bit_wait_timeout);
231 __sched int bit_wait_io_timeout(struct wait_bit_key *word, int mode)
233 unsigned long now = READ_ONCE(jiffies);
235 if (time_after_eq(now, word->timeout))
237 io_schedule_timeout(word->timeout - now);
238 if (signal_pending_state(mode, current))
243 EXPORT_SYMBOL_GPL(bit_wait_io_timeout);
245 void __init wait_bit_init(void)
249 for (i = 0; i < WAIT_TABLE_SIZE; i++)
250 init_waitqueue_head(bit_wait_table + i);