Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Generic waiting primitives. |
| 3 | * |
| 4 | * (C) 2004 William Irwin, Oracle |
| 5 | */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6 | #include <linux/init.h> |
| 7 | #include <linux/module.h> |
| 8 | #include <linux/sched.h> |
| 9 | #include <linux/mm.h> |
| 10 | #include <linux/wait.h> |
| 11 | #include <linux/hash.h> |
| 12 | |
Peter Zijlstra | 2fc3911 | 2009-08-10 12:33:05 +0100 | [diff] [blame] | 13 | void __init_waitqueue_head(wait_queue_head_t *q, struct lock_class_key *key) |
Ingo Molnar | 21d71f5 | 2006-07-10 04:45:32 -0700 | [diff] [blame] | 14 | { |
| 15 | spin_lock_init(&q->lock); |
Peter Zijlstra | 2fc3911 | 2009-08-10 12:33:05 +0100 | [diff] [blame] | 16 | lockdep_set_class(&q->lock, key); |
Ingo Molnar | 21d71f5 | 2006-07-10 04:45:32 -0700 | [diff] [blame] | 17 | INIT_LIST_HEAD(&q->task_list); |
| 18 | } |
Ingo Molnar | eb4542b | 2006-07-03 00:25:07 -0700 | [diff] [blame] | 19 | |
Peter Zijlstra | 2fc3911 | 2009-08-10 12:33:05 +0100 | [diff] [blame] | 20 | EXPORT_SYMBOL(__init_waitqueue_head); |
Ingo Molnar | eb4542b | 2006-07-03 00:25:07 -0700 | [diff] [blame] | 21 | |
Harvey Harrison | 7ad5b3a | 2008-02-08 04:19:53 -0800 | [diff] [blame] | 22 | void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 23 | { |
| 24 | unsigned long flags; |
| 25 | |
| 26 | wait->flags &= ~WQ_FLAG_EXCLUSIVE; |
| 27 | spin_lock_irqsave(&q->lock, flags); |
| 28 | __add_wait_queue(q, wait); |
| 29 | spin_unlock_irqrestore(&q->lock, flags); |
| 30 | } |
| 31 | EXPORT_SYMBOL(add_wait_queue); |
| 32 | |
Harvey Harrison | 7ad5b3a | 2008-02-08 04:19:53 -0800 | [diff] [blame] | 33 | void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 34 | { |
| 35 | unsigned long flags; |
| 36 | |
| 37 | wait->flags |= WQ_FLAG_EXCLUSIVE; |
| 38 | spin_lock_irqsave(&q->lock, flags); |
| 39 | __add_wait_queue_tail(q, wait); |
| 40 | spin_unlock_irqrestore(&q->lock, flags); |
| 41 | } |
| 42 | EXPORT_SYMBOL(add_wait_queue_exclusive); |
| 43 | |
Harvey Harrison | 7ad5b3a | 2008-02-08 04:19:53 -0800 | [diff] [blame] | 44 | void remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 45 | { |
| 46 | unsigned long flags; |
| 47 | |
| 48 | spin_lock_irqsave(&q->lock, flags); |
| 49 | __remove_wait_queue(q, wait); |
| 50 | spin_unlock_irqrestore(&q->lock, flags); |
| 51 | } |
| 52 | EXPORT_SYMBOL(remove_wait_queue); |
| 53 | |
| 54 | |
| 55 | /* |
| 56 | * Note: we use "set_current_state()" _after_ the wait-queue add, |
| 57 | * because we need a memory barrier there on SMP, so that any |
| 58 | * wake-function that tests for the wait-queue being active |
| 59 | * will be guaranteed to see waitqueue addition _or_ subsequent |
| 60 | * tests in this thread will see the wakeup having taken place. |
| 61 | * |
| 62 | * The spin_unlock() itself is semi-permeable and only protects |
| 63 | * one way (it only protects stuff inside the critical region and |
| 64 | * stops them from bleeding out - it would still allow subsequent |
Michael Opdenacker | 59c5159 | 2007-05-09 08:57:56 +0200 | [diff] [blame] | 65 | * loads to move into the critical region). |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 66 | */ |
Harvey Harrison | 7ad5b3a | 2008-02-08 04:19:53 -0800 | [diff] [blame] | 67 | void |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 68 | prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state) |
| 69 | { |
| 70 | unsigned long flags; |
| 71 | |
| 72 | wait->flags &= ~WQ_FLAG_EXCLUSIVE; |
| 73 | spin_lock_irqsave(&q->lock, flags); |
| 74 | if (list_empty(&wait->task_list)) |
| 75 | __add_wait_queue(q, wait); |
Tejun Heo | a25d644 | 2008-10-15 22:01:38 -0700 | [diff] [blame] | 76 | set_current_state(state); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 77 | spin_unlock_irqrestore(&q->lock, flags); |
| 78 | } |
| 79 | EXPORT_SYMBOL(prepare_to_wait); |
| 80 | |
Harvey Harrison | 7ad5b3a | 2008-02-08 04:19:53 -0800 | [diff] [blame] | 81 | void |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 82 | prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state) |
| 83 | { |
| 84 | unsigned long flags; |
| 85 | |
| 86 | wait->flags |= WQ_FLAG_EXCLUSIVE; |
| 87 | spin_lock_irqsave(&q->lock, flags); |
| 88 | if (list_empty(&wait->task_list)) |
| 89 | __add_wait_queue_tail(q, wait); |
Tejun Heo | a25d644 | 2008-10-15 22:01:38 -0700 | [diff] [blame] | 90 | set_current_state(state); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 91 | spin_unlock_irqrestore(&q->lock, flags); |
| 92 | } |
| 93 | EXPORT_SYMBOL(prepare_to_wait_exclusive); |
| 94 | |
Johannes Weiner | 777c6c5 | 2009-02-04 15:12:14 -0800 | [diff] [blame] | 95 | /* |
| 96 | * finish_wait - clean up after waiting in a queue |
| 97 | * @q: waitqueue waited on |
| 98 | * @wait: wait descriptor |
| 99 | * |
| 100 | * Sets current thread back to running state and removes |
| 101 | * the wait descriptor from the given waitqueue if still |
| 102 | * queued. |
| 103 | */ |
Harvey Harrison | 7ad5b3a | 2008-02-08 04:19:53 -0800 | [diff] [blame] | 104 | void finish_wait(wait_queue_head_t *q, wait_queue_t *wait) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 105 | { |
| 106 | unsigned long flags; |
| 107 | |
| 108 | __set_current_state(TASK_RUNNING); |
| 109 | /* |
| 110 | * We can check for list emptiness outside the lock |
| 111 | * IFF: |
| 112 | * - we use the "careful" check that verifies both |
| 113 | * the next and prev pointers, so that there cannot |
| 114 | * be any half-pending updates in progress on other |
| 115 | * CPU's that we haven't seen yet (and that might |
| 116 | * still change the stack area. |
| 117 | * and |
| 118 | * - all other users take the lock (ie we can only |
| 119 | * have _one_ other CPU that looks at or modifies |
| 120 | * the list). |
| 121 | */ |
| 122 | if (!list_empty_careful(&wait->task_list)) { |
| 123 | spin_lock_irqsave(&q->lock, flags); |
| 124 | list_del_init(&wait->task_list); |
| 125 | spin_unlock_irqrestore(&q->lock, flags); |
| 126 | } |
| 127 | } |
| 128 | EXPORT_SYMBOL(finish_wait); |
| 129 | |
Johannes Weiner | 777c6c5 | 2009-02-04 15:12:14 -0800 | [diff] [blame] | 130 | /* |
| 131 | * abort_exclusive_wait - abort exclusive waiting in a queue |
| 132 | * @q: waitqueue waited on |
| 133 | * @wait: wait descriptor |
| 134 | * @state: runstate of the waiter to be woken |
| 135 | * @key: key to identify a wait bit queue or %NULL |
| 136 | * |
| 137 | * Sets current thread back to running state and removes |
| 138 | * the wait descriptor from the given waitqueue if still |
| 139 | * queued. |
| 140 | * |
| 141 | * Wakes up the next waiter if the caller is concurrently |
| 142 | * woken up through the queue. |
| 143 | * |
| 144 | * This prevents waiter starvation where an exclusive waiter |
| 145 | * aborts and is woken up concurrently and noone wakes up |
| 146 | * the next waiter. |
| 147 | */ |
| 148 | void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, |
| 149 | unsigned int mode, void *key) |
| 150 | { |
| 151 | unsigned long flags; |
| 152 | |
| 153 | __set_current_state(TASK_RUNNING); |
| 154 | spin_lock_irqsave(&q->lock, flags); |
| 155 | if (!list_empty(&wait->task_list)) |
| 156 | list_del_init(&wait->task_list); |
| 157 | else if (waitqueue_active(q)) |
Johannes Weiner | 78ddb08 | 2009-04-14 16:53:05 +0200 | [diff] [blame] | 158 | __wake_up_locked_key(q, mode, key); |
Johannes Weiner | 777c6c5 | 2009-02-04 15:12:14 -0800 | [diff] [blame] | 159 | spin_unlock_irqrestore(&q->lock, flags); |
| 160 | } |
| 161 | EXPORT_SYMBOL(abort_exclusive_wait); |
| 162 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 163 | int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key) |
| 164 | { |
| 165 | int ret = default_wake_function(wait, mode, sync, key); |
| 166 | |
| 167 | if (ret) |
| 168 | list_del_init(&wait->task_list); |
| 169 | return ret; |
| 170 | } |
| 171 | EXPORT_SYMBOL(autoremove_wake_function); |
| 172 | |
| 173 | int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *arg) |
| 174 | { |
| 175 | struct wait_bit_key *key = arg; |
| 176 | struct wait_bit_queue *wait_bit |
| 177 | = container_of(wait, struct wait_bit_queue, wait); |
| 178 | |
| 179 | if (wait_bit->key.flags != key->flags || |
| 180 | wait_bit->key.bit_nr != key->bit_nr || |
| 181 | test_bit(key->bit_nr, key->flags)) |
| 182 | return 0; |
| 183 | else |
| 184 | return autoremove_wake_function(wait, mode, sync, key); |
| 185 | } |
| 186 | EXPORT_SYMBOL(wake_bit_function); |
| 187 | |
| 188 | /* |
| 189 | * To allow interruptible waiting and asynchronous (i.e. nonblocking) |
| 190 | * waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are |
| 191 | * permitted return codes. Nonzero return codes halt waiting and return. |
| 192 | */ |
Harvey Harrison | 7ad5b3a | 2008-02-08 04:19:53 -0800 | [diff] [blame] | 193 | int __sched |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 194 | __wait_on_bit(wait_queue_head_t *wq, struct wait_bit_queue *q, |
| 195 | int (*action)(void *), unsigned mode) |
| 196 | { |
| 197 | int ret = 0; |
| 198 | |
| 199 | do { |
| 200 | prepare_to_wait(wq, &q->wait, mode); |
| 201 | if (test_bit(q->key.bit_nr, q->key.flags)) |
| 202 | ret = (*action)(q->key.flags); |
| 203 | } while (test_bit(q->key.bit_nr, q->key.flags) && !ret); |
| 204 | finish_wait(wq, &q->wait); |
| 205 | return ret; |
| 206 | } |
| 207 | EXPORT_SYMBOL(__wait_on_bit); |
| 208 | |
Harvey Harrison | 7ad5b3a | 2008-02-08 04:19:53 -0800 | [diff] [blame] | 209 | int __sched out_of_line_wait_on_bit(void *word, int bit, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 210 | int (*action)(void *), unsigned mode) |
| 211 | { |
| 212 | wait_queue_head_t *wq = bit_waitqueue(word, bit); |
| 213 | DEFINE_WAIT_BIT(wait, word, bit); |
| 214 | |
| 215 | return __wait_on_bit(wq, &wait, action, mode); |
| 216 | } |
| 217 | EXPORT_SYMBOL(out_of_line_wait_on_bit); |
| 218 | |
Harvey Harrison | 7ad5b3a | 2008-02-08 04:19:53 -0800 | [diff] [blame] | 219 | int __sched |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 220 | __wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q, |
| 221 | int (*action)(void *), unsigned mode) |
| 222 | { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 223 | do { |
Johannes Weiner | 777c6c5 | 2009-02-04 15:12:14 -0800 | [diff] [blame] | 224 | int ret; |
| 225 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 226 | prepare_to_wait_exclusive(wq, &q->wait, mode); |
Johannes Weiner | 777c6c5 | 2009-02-04 15:12:14 -0800 | [diff] [blame] | 227 | if (!test_bit(q->key.bit_nr, q->key.flags)) |
| 228 | continue; |
| 229 | ret = action(q->key.flags); |
| 230 | if (!ret) |
| 231 | continue; |
| 232 | abort_exclusive_wait(wq, &q->wait, mode, &q->key); |
| 233 | return ret; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 234 | } while (test_and_set_bit(q->key.bit_nr, q->key.flags)); |
| 235 | finish_wait(wq, &q->wait); |
Johannes Weiner | 777c6c5 | 2009-02-04 15:12:14 -0800 | [diff] [blame] | 236 | return 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 237 | } |
| 238 | EXPORT_SYMBOL(__wait_on_bit_lock); |
| 239 | |
Harvey Harrison | 7ad5b3a | 2008-02-08 04:19:53 -0800 | [diff] [blame] | 240 | int __sched out_of_line_wait_on_bit_lock(void *word, int bit, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 241 | int (*action)(void *), unsigned mode) |
| 242 | { |
| 243 | wait_queue_head_t *wq = bit_waitqueue(word, bit); |
| 244 | DEFINE_WAIT_BIT(wait, word, bit); |
| 245 | |
| 246 | return __wait_on_bit_lock(wq, &wait, action, mode); |
| 247 | } |
| 248 | EXPORT_SYMBOL(out_of_line_wait_on_bit_lock); |
| 249 | |
Harvey Harrison | 7ad5b3a | 2008-02-08 04:19:53 -0800 | [diff] [blame] | 250 | void __wake_up_bit(wait_queue_head_t *wq, void *word, int bit) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 251 | { |
| 252 | struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit); |
| 253 | if (waitqueue_active(wq)) |
Matthew Wilcox | e64d66c | 2007-12-06 17:34:36 -0500 | [diff] [blame] | 254 | __wake_up(wq, TASK_NORMAL, 1, &key); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 255 | } |
| 256 | EXPORT_SYMBOL(__wake_up_bit); |
| 257 | |
| 258 | /** |
| 259 | * wake_up_bit - wake up a waiter on a bit |
| 260 | * @word: the word being waited on, a kernel virtual address |
| 261 | * @bit: the bit of the word being waited on |
| 262 | * |
| 263 | * There is a standard hashed waitqueue table for generic use. This |
| 264 | * is the part of the hashtable's accessor API that wakes up waiters |
| 265 | * on a bit. For instance, if one were to have waiters on a bitflag, |
| 266 | * one would call wake_up_bit() after clearing the bit. |
| 267 | * |
| 268 | * In order for this to function properly, as it uses waitqueue_active() |
| 269 | * internally, some kind of memory barrier must be done prior to calling |
| 270 | * this. Typically, this will be smp_mb__after_clear_bit(), but in some |
| 271 | * cases where bitflags are manipulated non-atomically under a lock, one |
| 272 | * may need to use a less regular barrier, such fs/inode.c's smp_mb(), |
| 273 | * because spin_unlock() does not guarantee a memory barrier. |
| 274 | */ |
Harvey Harrison | 7ad5b3a | 2008-02-08 04:19:53 -0800 | [diff] [blame] | 275 | void wake_up_bit(void *word, int bit) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 276 | { |
| 277 | __wake_up_bit(bit_waitqueue(word, bit), word, bit); |
| 278 | } |
| 279 | EXPORT_SYMBOL(wake_up_bit); |
| 280 | |
Harvey Harrison | 7ad5b3a | 2008-02-08 04:19:53 -0800 | [diff] [blame] | 281 | wait_queue_head_t *bit_waitqueue(void *word, int bit) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 282 | { |
| 283 | const int shift = BITS_PER_LONG == 32 ? 5 : 6; |
| 284 | const struct zone *zone = page_zone(virt_to_page(word)); |
| 285 | unsigned long val = (unsigned long)word << shift | bit; |
| 286 | |
| 287 | return &zone->wait_table[hash_long(val, zone->wait_table_bits)]; |
| 288 | } |
| 289 | EXPORT_SYMBOL(bit_waitqueue); |