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/*

 * Generic waiting primitives.

 *

 * (C) 2004 William Irwin, Oracle

 */

#include <linux/init.h>

#include <linux/module.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)

{

        spin_lock_init(&q->lock);

        INIT_LIST_HEAD(&q->task_list);

}

EXPORT_SYMBOL(init_waitqueue_head);

void fastcall 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 fastcall 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 fastcall 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 fastcall

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);

        /*

         * don't alter the task state if this is just going to

         * queue an async wait queue callback

         */

        if (is_sync_wait(wait))

                set_current_state(state);

        spin_unlock_irqrestore(&q->lock, flags);

}

EXPORT_SYMBOL(prepare_to_wait);

void fastcall

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);

        /*

         * don't alter the task state if this is just going to

         * queue an async wait queue callback

         */

        if (is_sync_wait(wait))

                set_current_state(state);

        spin_unlock_irqrestore(&q->lock, flags);

}

EXPORT_SYMBOL(prepare_to_wait_exclusive);

void fastcall 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);

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);

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 fastcall

__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);

int __sched fastcall 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 fastcall

__wait_on_bit_lock(wait_queue_head_t *wq, struct wait_bit_queue *q,

                        int (*action)(void *), unsigned mode)

{

        int ret = 0;

        do {

                prepare_to_wait_exclusive(wq, &q->wait, mode);

                if (test_bit(q->key.bit_nr, q->key.flags)) {

                        if ((ret = (*action)(q->key.flags)))

                                break;

                }

        } while (test_and_set_bit(q->key.bit_nr, q->key.flags));

        finish_wait(wq, &q->wait);

        return ret;

}

EXPORT_SYMBOL(__wait_on_bit_lock);

int __sched fastcall 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 fastcall __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_INTERRUPTIBLE|TASK_UNINTERRUPTIBLE, 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 fastcall wake_up_bit(void *word, int bit)

{

        __wake_up_bit(bit_waitqueue(word, bit), word, bit);

}

EXPORT_SYMBOL(wake_up_bit);

fastcall 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);