Linux 4.15.6
[linux/fpc-iii.git] / kernel / sched / wait_bit.c
blob84cb3acd926046cf703bf64a92493d85b7c40582
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>
7 #include <linux/hash.h>
9 #define WAIT_TABLE_BITS 8
10 #define WAIT_TABLE_SIZE (1 << WAIT_TABLE_BITS)
12 static wait_queue_head_t bit_wait_table[WAIT_TABLE_SIZE] __cacheline_aligned;
14 wait_queue_head_t *bit_waitqueue(void *word, int bit)
16 const int shift = BITS_PER_LONG == 32 ? 5 : 6;
17 unsigned long val = (unsigned long)word << shift | bit;
19 return bit_wait_table + hash_long(val, WAIT_TABLE_BITS);
21 EXPORT_SYMBOL(bit_waitqueue);
23 int wake_bit_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *arg)
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);
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);
35 EXPORT_SYMBOL(wake_bit_function);
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.
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)
46 int ret = 0;
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;
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;
76 return __wait_on_bit(wq_head, &wq_entry, action, mode);
78 EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout);
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)
84 int ret = 0;
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);
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().
96 if (ret)
97 finish_wait(wq_head, &wbq_entry->wq_entry);
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;
108 EXPORT_SYMBOL(__wait_on_bit_lock);
110 int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
111 wait_bit_action_f *action, unsigned mode)
113 struct wait_queue_head *wq_head = bit_waitqueue(word, bit);
114 DEFINE_WAIT_BIT(wq_entry, word, bit);
116 return __wait_on_bit_lock(wq_head, &wq_entry, action, mode);
118 EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
120 void __wake_up_bit(struct wait_queue_head *wq_head, void *word, int bit)
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);
126 EXPORT_SYMBOL(__wake_up_bit);
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
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.
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.
145 void wake_up_bit(void *word, int bit)
147 __wake_up_bit(bit_waitqueue(word, bit), word, bit);
149 EXPORT_SYMBOL(wake_up_bit);
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).
156 static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p)
158 if (BITS_PER_LONG == 64) {
159 unsigned long q = (unsigned long)p;
160 return bit_waitqueue((void *)(q & ~1), q & 1);
162 return bit_waitqueue(p, 0);
165 static int wake_atomic_t_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync,
166 void *arg)
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;
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);
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.
184 static __sched
185 int __wait_on_atomic_t(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry,
186 wait_atomic_t_action_f action, unsigned int mode)
188 atomic_t *val;
189 int ret = 0;
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;
196 ret = (*action)(val, mode);
197 } while (!ret && atomic_read(val) != 0);
198 finish_wait(wq_head, &wbq_entry->wq_entry);
199 return ret;
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, \
208 .entry = \
209 LIST_HEAD_INIT((name).wq_entry.entry), \
210 }, \
213 __sched int out_of_line_wait_on_atomic_t(atomic_t *p,
214 wait_atomic_t_action_f action,
215 unsigned int mode)
217 struct wait_queue_head *wq_head = atomic_t_waitqueue(p);
218 DEFINE_WAIT_ATOMIC_T(wq_entry, p);
220 return __wait_on_atomic_t(wq_head, &wq_entry, action, mode);
222 EXPORT_SYMBOL(out_of_line_wait_on_atomic_t);
224 __sched int atomic_t_wait(atomic_t *counter, unsigned int mode)
226 schedule();
227 if (signal_pending_state(mode, current))
228 return -EINTR;
229 return 0;
231 EXPORT_SYMBOL(atomic_t_wait);
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
237 * Wake up anyone waiting for the atomic_t to go to zero.
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).
242 void wake_up_atomic_t(atomic_t *p)
244 __wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR);
246 EXPORT_SYMBOL(wake_up_atomic_t);
248 __sched int bit_wait(struct wait_bit_key *word, int mode)
250 schedule();
251 if (signal_pending_state(mode, current))
252 return -EINTR;
253 return 0;
255 EXPORT_SYMBOL(bit_wait);
257 __sched int bit_wait_io(struct wait_bit_key *word, int mode)
259 io_schedule();
260 if (signal_pending_state(mode, current))
261 return -EINTR;
262 return 0;
264 EXPORT_SYMBOL(bit_wait_io);
266 __sched int bit_wait_timeout(struct wait_bit_key *word, int mode)
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;
276 EXPORT_SYMBOL_GPL(bit_wait_timeout);
278 __sched int bit_wait_io_timeout(struct wait_bit_key *word, int mode)
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;
288 EXPORT_SYMBOL_GPL(bit_wait_io_timeout);
290 void __init wait_bit_init(void)
292 int i;
294 for (i = 0; i < WAIT_TABLE_SIZE; i++)
295 init_waitqueue_head(bit_wait_table + i);