| /* |
| * Generic waiting primitives. |
| * |
| * (C) 2004 Nadia Yvette Chambers, Oracle |
| */ |
| #include <linux/init.h> |
| #include <linux/export.h> |
| #include <linux/sched.h> |
| #include <linux/mm.h> |
| #include <linux/wait.h> |
| #include <linux/hash.h> |
| |
| void __init_waitqueue_head(wait_queue_head_t *q, const char *name, struct lock_class_key *key) |
| { |
| spin_lock_init(&q->lock); |
| lockdep_set_class_and_name(&q->lock, key, name); |
| INIT_LIST_HEAD(&q->task_list); |
| } |
| |
| EXPORT_SYMBOL(__init_waitqueue_head); |
| |
| void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait) |
| { |
| unsigned long flags; |
| |
| wait->flags &= ~WQ_FLAG_EXCLUSIVE; |
| spin_lock_irqsave(&q->lock, flags); |
| __add_wait_queue(q, wait); |
| spin_unlock_irqrestore(&q->lock, flags); |
| } |
| EXPORT_SYMBOL(add_wait_queue); |
| |
| void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait) |
| { |
| unsigned long flags; |
| |
| wait->flags |= WQ_FLAG_EXCLUSIVE; |
| spin_lock_irqsave(&q->lock, flags); |
| __add_wait_queue_tail(q, wait); |
| spin_unlock_irqrestore(&q->lock, flags); |
| } |
| EXPORT_SYMBOL(add_wait_queue_exclusive); |
| |
| void remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait) |
| { |
| unsigned long flags; |
| |
| spin_lock_irqsave(&q->lock, flags); |
| __remove_wait_queue(q, wait); |
| spin_unlock_irqrestore(&q->lock, flags); |
| } |
| EXPORT_SYMBOL(remove_wait_queue); |
| |
| |
| /* |
| * Note: we use "set_current_state()" _after_ the wait-queue add, |
| * because we need a memory barrier there on SMP, so that any |
| * wake-function that tests for the wait-queue being active |
| * will be guaranteed to see waitqueue addition _or_ subsequent |
| * tests in this thread will see the wakeup having taken place. |
| * |
| * The spin_unlock() itself is semi-permeable and only protects |
| * one way (it only protects stuff inside the critical region and |
| * stops them from bleeding out - it would still allow subsequent |
| * loads to move into the critical region). |
| */ |
| void |
| prepare_to_wait(wait_queue_head_t *q, wait_queue_t *wait, int state) |
| { |
| unsigned long flags; |
| |
| wait->flags &= ~WQ_FLAG_EXCLUSIVE; |
| spin_lock_irqsave(&q->lock, flags); |
| if (list_empty(&wait->task_list)) |
| __add_wait_queue(q, wait); |
| set_current_state(state); |
| spin_unlock_irqrestore(&q->lock, flags); |
| } |
| EXPORT_SYMBOL(prepare_to_wait); |
| |
| void |
| prepare_to_wait_exclusive(wait_queue_head_t *q, wait_queue_t *wait, int state) |
| { |
| unsigned long flags; |
| |
| wait->flags |= WQ_FLAG_EXCLUSIVE; |
| spin_lock_irqsave(&q->lock, flags); |
| if (list_empty(&wait->task_list)) |
| __add_wait_queue_tail(q, wait); |
| set_current_state(state); |
| spin_unlock_irqrestore(&q->lock, flags); |
| } |
| EXPORT_SYMBOL(prepare_to_wait_exclusive); |
| |
| /** |
| * finish_wait - clean up after waiting in a queue |
| * @q: waitqueue waited on |
| * @wait: wait descriptor |
| * |
| * Sets current thread back to running state and removes |
| * the wait descriptor from the given waitqueue if still |
| * queued. |
| */ |
| void finish_wait(wait_queue_head_t *q, wait_queue_t *wait) |
| { |
| unsigned long flags; |
| |
| __set_current_state(TASK_RUNNING); |
| /* |
| * We can check for list emptiness outside the lock |
| * IFF: |
| * - we use the "careful" check that verifies both |
| * the next and prev pointers, so that there cannot |
| * be any half-pending updates in progress on other |
| * CPU's that we haven't seen yet (and that might |
| * still change the stack area. |
| * and |
| * - all other users take the lock (ie we can only |
| * have _one_ other CPU that looks at or modifies |
| * the list). |
| */ |
| if (!list_empty_careful(&wait->task_list)) { |
| spin_lock_irqsave(&q->lock, flags); |
| list_del_init(&wait->task_list); |
| spin_unlock_irqrestore(&q->lock, flags); |
| } |
| } |
| EXPORT_SYMBOL(finish_wait); |
| |
| /** |
| * abort_exclusive_wait - abort exclusive waiting in a queue |
| * @q: waitqueue waited on |
| * @wait: wait descriptor |
| * @mode: runstate of the waiter to be woken |
| * @key: key to identify a wait bit queue or %NULL |
| * |
| * Sets current thread back to running state and removes |
| * the wait descriptor from the given waitqueue if still |
| * queued. |
| * |
| * Wakes up the next waiter if the caller is concurrently |
| * woken up through the queue. |
| * |
| * This prevents waiter starvation where an exclusive waiter |
| * aborts and is woken up concurrently and no one wakes up |
| * the next waiter. |
| */ |
| void abort_exclusive_wait(wait_queue_head_t *q, wait_queue_t *wait, |
| unsigned int mode, void *key) |
| { |
| unsigned long flags; |
| |
| __set_current_state(TASK_RUNNING); |
| spin_lock_irqsave(&q->lock, flags); |
| if (!list_empty(&wait->task_list)) |
| list_del_init(&wait->task_list); |
| else if (waitqueue_active(q)) |
| __wake_up_locked_key(q, mode, key); |
| spin_unlock_irqrestore(&q->lock, flags); |
| } |
| EXPORT_SYMBOL(abort_exclusive_wait); |
| |
| int autoremove_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key) |
| { |
| int ret = default_wake_function(wait, mode, sync, key); |
| |
| if (ret) |
| list_del_init(&wait->task_list); |
| return ret; |
| } |
| EXPORT_SYMBOL(autoremove_wake_function); |
| |
| |
| /* |
| * DEFINE_WAIT_FUNC(wait, woken_wake_func); |
| * |
| * add_wait_queue(&wq, &wait); |
| * for (;;) { |
| * if (condition) |
| * break; |
| * |
| * p->state = mode; condition = true; |
| * smp_mb(); // A smp_wmb(); // C |
| * if (!wait->flags & WQ_FLAG_WOKEN) wait->flags |= WQ_FLAG_WOKEN; |
| * schedule() try_to_wake_up(); |
| * p->state = TASK_RUNNING; ~~~~~~~~~~~~~~~~~~ |
| * wait->flags &= ~WQ_FLAG_WOKEN; condition = true; |
| * smp_mb() // B smp_wmb(); // C |
| * wait->flags |= WQ_FLAG_WOKEN; |
| * } |
| * remove_wait_queue(&wq, &wait); |
| * |
| */ |
| long wait_woken(wait_queue_t *wait, unsigned mode, long timeout) |
| { |
| set_current_state(mode); /* A */ |
| /* |
| * The above implies an smp_mb(), which matches with the smp_wmb() from |
| * woken_wake_function() such that if we observe WQ_FLAG_WOKEN we must |
| * also observe all state before the wakeup. |
| */ |
| if (!(wait->flags & WQ_FLAG_WOKEN)) |
| timeout = schedule_timeout(timeout); |
| __set_current_state(TASK_RUNNING); |
| |
| /* |
| * The below implies an smp_mb(), it too pairs with the smp_wmb() from |
| * woken_wake_function() such that we must either observe the wait |
| * condition being true _OR_ WQ_FLAG_WOKEN such that we will not miss |
| * an event. |
| */ |
| set_mb(wait->flags, wait->flags & ~WQ_FLAG_WOKEN); /* B */ |
| |
| return timeout; |
| } |
| EXPORT_SYMBOL(wait_woken); |
| |
| int woken_wake_function(wait_queue_t *wait, unsigned mode, int sync, void *key) |
| { |
| /* |
| * Although this function is called under waitqueue lock, LOCK |
| * doesn't imply write barrier and the users expects write |
| * barrier semantics on wakeup functions. The following |
| * smp_wmb() is equivalent to smp_wmb() in try_to_wake_up() |
| * and is paired with set_mb() in wait_woken(). |
| */ |
| smp_wmb(); /* C */ |
| wait->flags |= WQ_FLAG_WOKEN; |
| |
| return default_wake_function(wait, mode, sync, key); |
| } |
| EXPORT_SYMBOL(woken_wake_function); |
| |
| int wake_bit_function(wait_queue_t *wait, unsigned mode, int sync, void *arg) |
| { |
| struct wait_bit_key *key = arg; |
| struct wait_bit_queue *wait_bit |
| = container_of(wait, struct wait_bit_queue, wait); |
| |
| if (wait_bit->key.flags != key->flags || |
| wait_bit->key.bit_nr != key->bit_nr || |
| test_bit(key->bit_nr, key->flags)) |
| return 0; |
| else |
| return autoremove_wake_function(wait, mode, sync, key); |
| } |
| EXPORT_SYMBOL(wake_bit_function); |
| |
| /* |
| * To allow interruptible waiting and asynchronous (i.e. nonblocking) |
| * waiting, the actions of __wait_on_bit() and __wait_on_bit_lock() are |
| * permitted return codes. Nonzero return codes halt waiting and return. |
| */ |
| int __sched |
| __wait_on_bit(wait_queue_head_t *wq, struct wait_bit_queue *q, |
| int (*action)(void *), unsigned mode) |
| { |
| int ret = 0; |
| |
| do { |
| prepare_to_wait(wq, &q->wait, mode); |
| if (test_bit(q->key.bit_nr, q->key.flags)) |
| ret = (*action)(q->key.flags); |
| } while (test_bit(q->key.bit_nr, q->key.flags) && !ret); |
| finish_wait(wq, &q->wait); |
| return ret; |
| } |
| EXPORT_SYMBOL(__wait_on_bit); |
| |
| static int __wait_on_bit_with_action_f(wait_queue_head_t *wq, |
| struct wait_bit_queue *q, |
| wait_bit_action_f *action, |
| unsigned mode) |
| { |
| int ret = 0; |
| |
| do { |
| prepare_to_wait(wq, &q->wait, mode); |
| if (test_bit(q->key.bit_nr, q->key.flags)) |
| ret = (*action)(&q->key); |
| } while (test_bit(q->key.bit_nr, q->key.flags) && !ret); |
| finish_wait(wq, &q->wait); |
| return ret; |
| } |
| |
| int __sched out_of_line_wait_on_bit(void *word, int bit, |
| int (*action)(void *), unsigned mode) |
| { |
| wait_queue_head_t *wq = bit_waitqueue(word, bit); |
| DEFINE_WAIT_BIT(wait, word, bit); |
| |
| return __wait_on_bit(wq, &wait, action, mode); |
| } |
| EXPORT_SYMBOL(out_of_line_wait_on_bit); |
| |
| int __sched out_of_line_wait_on_bit_timeout( |
| void *word, int bit, wait_bit_action_f *action, |
| unsigned mode, unsigned long timeout) |
| { |
| wait_queue_head_t *wq = bit_waitqueue(word, bit); |
| DEFINE_WAIT_BIT(wait, word, bit); |
| |
| wait.key.timeout = jiffies + timeout; |
| return __wait_on_bit_with_action_f(wq, &wait, action, mode); |
| } |
| EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout); |
| |
| int __sched |
| __wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q, |
| int (*action)(void *), unsigned mode) |
| { |
| do { |
| int ret; |
| |
| prepare_to_wait_exclusive(wq, &q->wait, mode); |
| if (!test_bit(q->key.bit_nr, q->key.flags)) |
| continue; |
| ret = action(q->key.flags); |
| if (!ret) |
| continue; |
| abort_exclusive_wait(wq, &q->wait, mode, &q->key); |
| return ret; |
| } while (test_and_set_bit(q->key.bit_nr, q->key.flags)); |
| finish_wait(wq, &q->wait); |
| return 0; |
| } |
| EXPORT_SYMBOL(__wait_on_bit_lock); |
| |
| int __sched out_of_line_wait_on_bit_lock(void *word, int bit, |
| int (*action)(void *), unsigned mode) |
| { |
| wait_queue_head_t *wq = bit_waitqueue(word, bit); |
| DEFINE_WAIT_BIT(wait, word, bit); |
| |
| return __wait_on_bit_lock(wq, &wait, action, mode); |
| } |
| EXPORT_SYMBOL(out_of_line_wait_on_bit_lock); |
| |
| void __wake_up_bit(wait_queue_head_t *wq, void *word, int bit) |
| { |
| struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit); |
| if (waitqueue_active(wq)) |
| __wake_up(wq, TASK_NORMAL, 1, &key); |
| } |
| EXPORT_SYMBOL(__wake_up_bit); |
| |
| /** |
| * wake_up_bit - wake up a waiter on a bit |
| * @word: the word being waited on, a kernel virtual address |
| * @bit: the bit of the word being waited on |
| * |
| * There is a standard hashed waitqueue table for generic use. This |
| * is the part of the hashtable's accessor API that wakes up waiters |
| * on a bit. For instance, if one were to have waiters on a bitflag, |
| * one would call wake_up_bit() after clearing the bit. |
| * |
| * In order for this to function properly, as it uses waitqueue_active() |
| * internally, some kind of memory barrier must be done prior to calling |
| * this. Typically, this will be smp_mb__after_clear_bit(), but in some |
| * cases where bitflags are manipulated non-atomically under a lock, one |
| * may need to use a less regular barrier, such fs/inode.c's smp_mb(), |
| * because spin_unlock() does not guarantee a memory barrier. |
| */ |
| void wake_up_bit(void *word, int bit) |
| { |
| __wake_up_bit(bit_waitqueue(word, bit), word, bit); |
| } |
| EXPORT_SYMBOL(wake_up_bit); |
| |
| wait_queue_head_t *bit_waitqueue(void *word, int bit) |
| { |
| const int shift = BITS_PER_LONG == 32 ? 5 : 6; |
| const struct zone *zone = page_zone(virt_to_page(word)); |
| unsigned long val = (unsigned long)word << shift | bit; |
| |
| return &zone->wait_table[hash_long(val, zone->wait_table_bits)]; |
| } |
| EXPORT_SYMBOL(bit_waitqueue); |
| |
| __sched int bit_wait_timeout(struct wait_bit_key *word) |
| { |
| unsigned long now = ACCESS_ONCE(jiffies); |
| if (signal_pending_state(current->state, current)) |
| return 1; |
| if (time_after_eq(now, word->timeout)) |
| return -EAGAIN; |
| schedule_timeout(word->timeout - now); |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(bit_wait_timeout); |
| |
| __sched int bit_wait_io_timeout(struct wait_bit_key *word) |
| { |
| unsigned long now = ACCESS_ONCE(jiffies); |
| if (signal_pending_state(current->state, current)) |
| return 1; |
| if (time_after_eq(now, word->timeout)) |
| return -EAGAIN; |
| io_schedule_timeout(word->timeout - now); |
| return 0; |
| } |
| EXPORT_SYMBOL_GPL(bit_wait_io_timeout); |