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(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 } 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. 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 */ 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(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(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 } 66 EXPORT_SYMBOL(out_of_line_wait_on_bit); 67 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) 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(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 } 119 EXPORT_SYMBOL(out_of_line_wait_on_bit_lock); 120 121 void __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 } 128 EXPORT_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 */ 147 void wake_up_bit(void *word, int bit) 148 { 149 __wake_up_bit(bit_waitqueue(word, bit), word, bit); 150 } 151 EXPORT_SYMBOL(wake_up_bit); 152 153 wait_queue_head_t *__var_waitqueue(void *p) 154 { 155 return bit_wait_table + hash_ptr(p, WAIT_TABLE_BITS); 156 } 157 EXPORT_SYMBOL(__var_waitqueue); 158 159 static int 160 var_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 } 173 174 void 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 } 189 EXPORT_SYMBOL(init_wait_var_entry); 190 191 void wake_up_var(void *var) 192 { 193 __wake_up_bit(__var_waitqueue(var), var, -1); 194 } 195 EXPORT_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 } 205 EXPORT_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 } 215 EXPORT_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 } 229 EXPORT_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 } 243 EXPORT_SYMBOL_GPL(bit_wait_io_timeout); 244 245 void __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 } 252