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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
10static wait_queue_head_t bit_wait_table[WAIT_TABLE_SIZE] __cacheline_aligned;
11
12wait_queue_head_t *bit_waitqueue(unsigned long *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}
19EXPORT_SYMBOL(bit_waitqueue);
20
21int 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;
30
31 return autoremove_wake_function(wq_entry, mode, sync, key);
32}
33EXPORT_SYMBOL(wake_bit_function);
34
35/*
36 * To allow interruptible waiting and asynchronous (i.e. non-blocking)
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 */
40int __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_acquire(wbq_entry->key.bit_nr, wbq_entry->key.flags) && !ret);
51
52 finish_wait(wq_head, &wbq_entry->wq_entry);
53
54 return ret;
55}
56EXPORT_SYMBOL(__wait_on_bit);
57
58int __sched out_of_line_wait_on_bit(unsigned long *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}
66EXPORT_SYMBOL(out_of_line_wait_on_bit);
67
68int __sched out_of_line_wait_on_bit_timeout(
69 unsigned long *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
77 return __wait_on_bit(wq_head, &wq_entry, action, mode);
78}
79EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout);
80
81int __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}
109EXPORT_SYMBOL(__wait_on_bit_lock);
110
111int __sched out_of_line_wait_on_bit_lock(unsigned long *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}
119EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
120
121void __wake_up_bit(struct wait_queue_head *wq_head, unsigned long *word, int bit)
122{
123 struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
124
125 if (waitqueue_active(wq_head))
126 __wake_up(wq_head, TASK_NORMAL, 1, &key);
127}
128EXPORT_SYMBOL(__wake_up_bit);
129
130/**
131 * wake_up_bit - wake up waiters on a bit
132 * @word: the address containing the bit being waited on
133 * @bit: the bit at that address being waited on
134 *
135 * Wake up any process waiting in wait_on_bit() or similar for the
136 * given bit to be cleared.
137 *
138 * The wake-up is sent to tasks in a waitqueue selected by hash from a
139 * shared pool. Only those tasks on that queue which have requested
140 * wake_up on this specific address and bit will be woken, and only if the
141 * bit is clear.
142 *
143 * In order for this to function properly there must be a full memory
144 * barrier after the bit is cleared and before this function is called.
145 * If the bit was cleared atomically, such as a by clear_bit() then
146 * smb_mb__after_atomic() can be used, othwewise smb_mb() is needed.
147 * If the bit was cleared with a fully-ordered operation, no further
148 * barrier is required.
149 *
150 * Normally the bit should be cleared by an operation with RELEASE
151 * semantics so that any changes to memory made before the bit is
152 * cleared are guaranteed to be visible after the matching wait_on_bit()
153 * completes.
154 */
155void wake_up_bit(unsigned long *word, int bit)
156{
157 __wake_up_bit(bit_waitqueue(word, bit), word, bit);
158}
159EXPORT_SYMBOL(wake_up_bit);
160
161wait_queue_head_t *__var_waitqueue(void *p)
162{
163 return bit_wait_table + hash_ptr(p, WAIT_TABLE_BITS);
164}
165EXPORT_SYMBOL(__var_waitqueue);
166
167static int
168var_wake_function(struct wait_queue_entry *wq_entry, unsigned int mode,
169 int sync, void *arg)
170{
171 struct wait_bit_key *key = arg;
172 struct wait_bit_queue_entry *wbq_entry =
173 container_of(wq_entry, struct wait_bit_queue_entry, wq_entry);
174
175 if (wbq_entry->key.flags != key->flags ||
176 wbq_entry->key.bit_nr != key->bit_nr)
177 return 0;
178
179 return autoremove_wake_function(wq_entry, mode, sync, key);
180}
181
182void init_wait_var_entry(struct wait_bit_queue_entry *wbq_entry, void *var, int flags)
183{
184 *wbq_entry = (struct wait_bit_queue_entry){
185 .key = {
186 .flags = (var),
187 .bit_nr = -1,
188 },
189 .wq_entry = {
190 .flags = flags,
191 .private = current,
192 .func = var_wake_function,
193 .entry = LIST_HEAD_INIT(wbq_entry->wq_entry.entry),
194 },
195 };
196}
197EXPORT_SYMBOL(init_wait_var_entry);
198
199/**
200 * wake_up_var - wake up waiters on a variable (kernel address)
201 * @var: the address of the variable being waited on
202 *
203 * Wake up any process waiting in wait_var_event() or similar for the
204 * given variable to change. wait_var_event() can be waiting for an
205 * arbitrary condition to be true and associates that condition with an
206 * address. Calling wake_up_var() suggests that the condition has been
207 * made true, but does not strictly require the condtion to use the
208 * address given.
209 *
210 * The wake-up is sent to tasks in a waitqueue selected by hash from a
211 * shared pool. Only those tasks on that queue which have requested
212 * wake_up on this specific address will be woken.
213 *
214 * In order for this to function properly there must be a full memory
215 * barrier after the variable is updated (or more accurately, after the
216 * condition waited on has been made to be true) and before this function
217 * is called. If the variable was updated atomically, such as a by
218 * atomic_dec() then smb_mb__after_atomic() can be used. If the
219 * variable was updated by a fully ordered operation such as
220 * atomic_dec_and_test() then no extra barrier is required. Otherwise
221 * smb_mb() is needed.
222 *
223 * Normally the variable should be updated (the condition should be made
224 * to be true) by an operation with RELEASE semantics such as
225 * smp_store_release() so that any changes to memory made before the
226 * variable was updated are guaranteed to be visible after the matching
227 * wait_var_event() completes.
228 */
229void wake_up_var(void *var)
230{
231 __wake_up_bit(__var_waitqueue(var), var, -1);
232}
233EXPORT_SYMBOL(wake_up_var);
234
235__sched int bit_wait(struct wait_bit_key *word, int mode)
236{
237 schedule();
238 if (signal_pending_state(mode, current))
239 return -EINTR;
240
241 return 0;
242}
243EXPORT_SYMBOL(bit_wait);
244
245__sched int bit_wait_io(struct wait_bit_key *word, int mode)
246{
247 io_schedule();
248 if (signal_pending_state(mode, current))
249 return -EINTR;
250
251 return 0;
252}
253EXPORT_SYMBOL(bit_wait_io);
254
255__sched int bit_wait_timeout(struct wait_bit_key *word, int mode)
256{
257 unsigned long now = READ_ONCE(jiffies);
258
259 if (time_after_eq(now, word->timeout))
260 return -EAGAIN;
261 schedule_timeout(word->timeout - now);
262 if (signal_pending_state(mode, current))
263 return -EINTR;
264
265 return 0;
266}
267EXPORT_SYMBOL_GPL(bit_wait_timeout);
268
269void __init wait_bit_init(void)
270{
271 int i;
272
273 for (i = 0; i < WAIT_TABLE_SIZE; i++)
274 init_waitqueue_head(bit_wait_table + i);
275}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * The implementation of the wait_bit*() and related waiting APIs:
4 */
5#include "sched.h"
6
7#define WAIT_TABLE_BITS 8
8#define WAIT_TABLE_SIZE (1 << WAIT_TABLE_BITS)
9
10static wait_queue_head_t bit_wait_table[WAIT_TABLE_SIZE] __cacheline_aligned;
11
12wait_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}
19EXPORT_SYMBOL(bit_waitqueue);
20
21int 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;
30
31 return autoremove_wake_function(wq_entry, mode, sync, key);
32}
33EXPORT_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 */
40int __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);
51
52 finish_wait(wq_head, &wbq_entry->wq_entry);
53
54 return ret;
55}
56EXPORT_SYMBOL(__wait_on_bit);
57
58int __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}
66EXPORT_SYMBOL(out_of_line_wait_on_bit);
67
68int __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
77 return __wait_on_bit(wq_head, &wq_entry, action, mode);
78}
79EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout);
80
81int __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}
109EXPORT_SYMBOL(__wait_on_bit_lock);
110
111int __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}
119EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
120
121void __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);
124
125 if (waitqueue_active(wq_head))
126 __wake_up(wq_head, TASK_NORMAL, 1, &key);
127}
128EXPORT_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 */
147void wake_up_bit(void *word, int bit)
148{
149 __wake_up_bit(bit_waitqueue(word, bit), word, bit);
150}
151EXPORT_SYMBOL(wake_up_bit);
152
153wait_queue_head_t *__var_waitqueue(void *p)
154{
155 return bit_wait_table + hash_ptr(p, WAIT_TABLE_BITS);
156}
157EXPORT_SYMBOL(__var_waitqueue);
158
159static int
160var_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
174void 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 .flags = flags,
183 .private = current,
184 .func = var_wake_function,
185 .entry = LIST_HEAD_INIT(wbq_entry->wq_entry.entry),
186 },
187 };
188}
189EXPORT_SYMBOL(init_wait_var_entry);
190
191void wake_up_var(void *var)
192{
193 __wake_up_bit(__var_waitqueue(var), var, -1);
194}
195EXPORT_SYMBOL(wake_up_var);
196
197__sched int bit_wait(struct wait_bit_key *word, int mode)
198{
199 schedule();
200 if (signal_pending_state(mode, current))
201 return -EINTR;
202
203 return 0;
204}
205EXPORT_SYMBOL(bit_wait);
206
207__sched int bit_wait_io(struct wait_bit_key *word, int mode)
208{
209 io_schedule();
210 if (signal_pending_state(mode, current))
211 return -EINTR;
212
213 return 0;
214}
215EXPORT_SYMBOL(bit_wait_io);
216
217__sched int bit_wait_timeout(struct wait_bit_key *word, int mode)
218{
219 unsigned long now = READ_ONCE(jiffies);
220
221 if (time_after_eq(now, word->timeout))
222 return -EAGAIN;
223 schedule_timeout(word->timeout - now);
224 if (signal_pending_state(mode, current))
225 return -EINTR;
226
227 return 0;
228}
229EXPORT_SYMBOL_GPL(bit_wait_timeout);
230
231__sched int bit_wait_io_timeout(struct wait_bit_key *word, int mode)
232{
233 unsigned long now = READ_ONCE(jiffies);
234
235 if (time_after_eq(now, word->timeout))
236 return -EAGAIN;
237 io_schedule_timeout(word->timeout - now);
238 if (signal_pending_state(mode, current))
239 return -EINTR;
240
241 return 0;
242}
243EXPORT_SYMBOL_GPL(bit_wait_io_timeout);
244
245void __init wait_bit_init(void)
246{
247 int i;
248
249 for (i = 0; i < WAIT_TABLE_SIZE; i++)
250 init_waitqueue_head(bit_wait_table + i);
251}