1/* 2 * Generic waiting primitives. 3 * 4 * (C) 2004 William Irwin, Oracle 5 */ 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 13void init_waitqueue_head(wait_queue_head_t *q) 14{ 15 spin_lock_init(&q->lock); 16 INIT_LIST_HEAD(&q->task_list); 17} 18 19EXPORT_SYMBOL(init_waitqueue_head); 20 21void fastcall add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait) 22{ 23 unsigned long flags; 24 25 wait->flags &= ~WQ_FLAG_EXCLUSIVE; 26 spin_lock_irqsave(&q->lock, flags); 27 __add_wait_queue(q, wait); 28 spin_unlock_irqrestore(&q->lock, flags); 29} 30EXPORT_SYMBOL(add_wait_queue); 31 32void fastcall add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait) 33{ 34 unsigned long flags; 35 36 wait->flags |= WQ_FLAG_EXCLUSIVE; 37 spin_lock_irqsave(&q->lock, flags); 38 __add_wait_queue_tail(q, wait); 39 spin_unlock_irqrestore(&q->lock, flags); 40} 41EXPORT_SYMBOL(add_wait_queue_exclusive); 42 43void fastcall remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait) 44{ 45 unsigned long flags; 46 47 spin_lock_irqsave(&q->lock, flags); 48 __remove_wait_queue(q, wait); 49 spin_unlock_irqrestore(&q->lock, flags); 50} 51EXPORT_SYMBOL(remove_wait_queue); 52 53 54/* 55 * Note: we use "set_current_state()" _after_ the wait-queue add, 56 * because we need a memory barrier there on SMP, so that any 57 * wake-function that tests for the wait-queue being active 58 * will be guaranteed to see waitqueue addition _or_ subsequent 59 * tests in this thread will see the wakeup having taken place. 60 * 61 * The spin_unlock() itself is semi-permeable and only protects 62 * one way (it only protects stuff inside the critical region and 63 * stops them from bleeding out - it would still allow subsequent 64 * loads to move into the critical region). 65 */ 66void fastcall 67prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state) 68{ 69 unsigned long flags; 70 71 wait->flags &= ~WQ_FLAG_EXCLUSIVE; 72 spin_lock_irqsave(&q->lock, flags); 73 if (list_empty(&wait->task_list)) 74 __add_wait_queue(q, wait); 75 /* 76 * don't alter the task state if this is just going to 77 * queue an async wait queue callback 78 */ 79 if (is_sync_wait(wait)) 80 set_current_state(state); 81 spin_unlock_irqrestore(&q->lock, flags); 82} 83EXPORT_SYMBOL(prepare_to_wait); 84 85void fastcall 86prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state) 87{ 88 unsigned long flags; 89 90 wait->flags |= WQ_FLAG_EXCLUSIVE; 91 spin_lock_irqsave(&q->lock, flags); 92 if (list_empty(&wait->task_list)) 93 __add_wait_queue_tail(q, wait); 94 /* 95 * don't alter the task state if this is just going to 96 * queue an async wait queue callback 97 */ 98 if (is_sync_wait(wait)) 99 set_current_state(state); 100 spin_unlock_irqrestore(&q->lock, flags); 101} 102EXPORT_SYMBOL(prepare_to_wait_exclusive); 103 104void fastcall finish_wait(wait_queue_head_t *q, wait_queue_t *wait) 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} 128EXPORT_SYMBOL(finish_wait); 129 130int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key) 131{ 132 int ret = default_wake_function(wait, mode, sync, key); 133 134 if (ret) 135 list_del_init(&wait->task_list); 136 return ret; 137} 138EXPORT_SYMBOL(autoremove_wake_function); 139 140int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *arg) 141{ 142 struct wait_bit_key *key = arg; 143 struct wait_bit_queue *wait_bit 144 = container_of(wait, struct wait_bit_queue, wait); 145 146 if (wait_bit->key.flags != key->flags || 147 wait_bit->key.bit_nr != key->bit_nr || 148 test_bit(key->bit_nr, key->flags)) 149 return 0; 150 else 151 return autoremove_wake_function(wait, mode, sync, key); 152} 153EXPORT_SYMBOL(wake_bit_function); 154 155/* 156 * To allow interruptible waiting and asynchronous (i.e. nonblocking) 157 * waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are 158 * permitted return codes. Nonzero return codes halt waiting and return. 159 */ 160int __sched fastcall 161__wait_on_bit(wait_queue_head_t *wq, struct wait_bit_queue *q, 162 int (*action)(void *), unsigned mode) 163{ 164 int ret = 0; 165 166 do { 167 prepare_to_wait(wq, &q->wait, mode); 168 if (test_bit(q->key.bit_nr, q->key.flags)) 169 ret = (*action)(q->key.flags); 170 } while (test_bit(q->key.bit_nr, q->key.flags) && !ret); 171 finish_wait(wq, &q->wait); 172 return ret; 173} 174EXPORT_SYMBOL(__wait_on_bit); 175 176int __sched fastcall out_of_line_wait_on_bit(void *word, int bit, 177 int (*action)(void *), unsigned mode) 178{ 179 wait_queue_head_t *wq = bit_waitqueue(word, bit); 180 DEFINE_WAIT_BIT(wait, word, bit); 181 182 return __wait_on_bit(wq, &wait, action, mode); 183} 184EXPORT_SYMBOL(out_of_line_wait_on_bit); 185 186int __sched fastcall 187__wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q, 188 int (*action)(void *), unsigned mode) 189{ 190 int ret = 0; 191 192 do { 193 prepare_to_wait_exclusive(wq, &q->wait, mode); 194 if (test_bit(q->key.bit_nr, q->key.flags)) { 195 if ((ret = (*action)(q->key.flags))) 196 break; 197 } 198 } while (test_and_set_bit(q->key.bit_nr, q->key.flags)); 199 finish_wait(wq, &q->wait); 200 return ret; 201} 202EXPORT_SYMBOL(__wait_on_bit_lock); 203 204int __sched fastcall out_of_line_wait_on_bit_lock(void *word, int bit, 205 int (*action)(void *), unsigned mode) 206{ 207 wait_queue_head_t *wq = bit_waitqueue(word, bit); 208 DEFINE_WAIT_BIT(wait, word, bit); 209 210 return __wait_on_bit_lock(wq, &wait, action, mode); 211} 212EXPORT_SYMBOL(out_of_line_wait_on_bit_lock); 213 214void fastcall __wake_up_bit(wait_queue_head_t *wq, void *word, int bit) 215{ 216 struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit); 217 if (waitqueue_active(wq)) 218 __wake_up(wq, TASK_INTERRUPTIBLE|TASK_UNINTERRUPTIBLE, 1, &key); 219} 220EXPORT_SYMBOL(__wake_up_bit); 221 222/** 223 * wake_up_bit - wake up a waiter on a bit 224 * @word: the word being waited on, a kernel virtual address 225 * @bit: the bit of the word being waited on 226 * 227 * There is a standard hashed waitqueue table for generic use. This 228 * is the part of the hashtable's accessor API that wakes up waiters 229 * on a bit. For instance, if one were to have waiters on a bitflag, 230 * one would call wake_up_bit() after clearing the bit. 231 * 232 * In order for this to function properly, as it uses waitqueue_active() 233 * internally, some kind of memory barrier must be done prior to calling 234 * this. Typically, this will be smp_mb__after_clear_bit(), but in some 235 * cases where bitflags are manipulated non-atomically under a lock, one 236 * may need to use a less regular barrier, such fs/inode.c's smp_mb(), 237 * because spin_unlock() does not guarantee a memory barrier. 238 */ 239void fastcall wake_up_bit(void *word, int bit) 240{ 241 __wake_up_bit(bit_waitqueue(word, bit), word, bit); 242} 243EXPORT_SYMBOL(wake_up_bit); 244 245fastcall wait_queue_head_t *bit_waitqueue(void *word, int bit) 246{ 247 const int shift = BITS_PER_LONG == 32 ? 5 : 6; 248 const struct zone *zone = page_zone(virt_to_page(word)); 249 unsigned long val = (unsigned long)word << shift | bit; 250 251 return &zone->wait_table[hash_long(val, zone->wait_table_bits)]; 252} 253EXPORT_SYMBOL(bit_waitqueue); 254