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 10 static wait_queue_head_t bit_wait_table[WAIT_TABLE_SIZE] __cacheline_aligned; 11 12 wait_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 } 19 EXPORT_SYMBOL(bit_waitqueue); 20 21 int 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 } 33 EXPORT_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 */ 40 int __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 } 56 EXPORT_SYMBOL(__wait_on_bit); 57 58 int __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 } 66 EXPORT_SYMBOL(out_of_line_wait_on_bit); 67 68 int __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 } 79 EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout); 80 81 int __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 } 109 EXPORT_SYMBOL(__wait_on_bit_lock); 110 111 int __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 } 119 EXPORT_SYMBOL(out_of_line_wait_on_bit_lock); 120 121 void __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 } 128 EXPORT_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 */ 155 void wake_up_bit(unsigned long *word, int bit) 156 { 157 __wake_up_bit(bit_waitqueue(word, bit), word, bit); 158 } 159 EXPORT_SYMBOL(wake_up_bit); 160 161 wait_queue_head_t *__var_waitqueue(void *p) 162 { 163 return bit_wait_table + hash_ptr(p, WAIT_TABLE_BITS); 164 } 165 EXPORT_SYMBOL(__var_waitqueue); 166 167 static int 168 var_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 } 181 182 void 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 } 197 EXPORT_SYMBOL(init_wait_var_entry); 198 199 void wake_up_var(void *var) 200 { 201 __wake_up_bit(__var_waitqueue(var), var, -1); 202 } 203 EXPORT_SYMBOL(wake_up_var); 204 205 __sched int bit_wait(struct wait_bit_key *word, int mode) 206 { 207 schedule(); 208 if (signal_pending_state(mode, current)) 209 return -EINTR; 210 211 return 0; 212 } 213 EXPORT_SYMBOL(bit_wait); 214 215 __sched int bit_wait_io(struct wait_bit_key *word, int mode) 216 { 217 io_schedule(); 218 if (signal_pending_state(mode, current)) 219 return -EINTR; 220 221 return 0; 222 } 223 EXPORT_SYMBOL(bit_wait_io); 224 225 __sched int bit_wait_timeout(struct wait_bit_key *word, int mode) 226 { 227 unsigned long now = READ_ONCE(jiffies); 228 229 if (time_after_eq(now, word->timeout)) 230 return -EAGAIN; 231 schedule_timeout(word->timeout - now); 232 if (signal_pending_state(mode, current)) 233 return -EINTR; 234 235 return 0; 236 } 237 EXPORT_SYMBOL_GPL(bit_wait_timeout); 238 239 __sched int bit_wait_io_timeout(struct wait_bit_key *word, int mode) 240 { 241 unsigned long now = READ_ONCE(jiffies); 242 243 if (time_after_eq(now, word->timeout)) 244 return -EAGAIN; 245 io_schedule_timeout(word->timeout - now); 246 if (signal_pending_state(mode, current)) 247 return -EINTR; 248 249 return 0; 250 } 251 EXPORT_SYMBOL_GPL(bit_wait_io_timeout); 252 253 void __init wait_bit_init(void) 254 { 255 int i; 256 257 for (i = 0; i < WAIT_TABLE_SIZE; i++) 258 init_waitqueue_head(bit_wait_table + i); 259 } 260