// SPDX-License-Identifier: GPL-2.0-only
/*
* The implementation of the wait_bit*() and related waiting APIs:
*/
#define WAIT_TABLE_BITS 8
#define WAIT_TABLE_SIZE (1 << WAIT_TABLE_BITS)
static wait_queue_head_t bit_wait_table[WAIT_TABLE_SIZE] __cacheline_aligned;
wait_queue_head_t *bit_waitqueue(void *word, int bit)
{
const int shift = BITS_PER_LONG == 32 ? 5 : 6;
unsigned long val = (unsigned long)word << shift | bit;
return bit_wait_table + hash_long(val, WAIT_TABLE_BITS);
}
EXPORT_SYMBOL(bit_waitqueue);
int wake_bit_function(struct wait_queue_entry *wq_entry, unsigned mode, int sync, void *arg)
{
struct wait_bit_key *key = arg;
struct wait_bit_queue_entry *wait_bit = container_of(wq_entry, struct wait_bit_queue_entry, wq_entry);
if (wait_bit->key.flags != key->flags ||
wait_bit->key.bit_nr != key->bit_nr ||
test_bit(key->bit_nr, key->flags))
return 0;
return autoremove_wake_function(wq_entry, mode, sync, key);
}
EXPORT_SYMBOL(wake_bit_function);
/*
* To allow interruptible waiting and asynchronous (i.e. non-blocking)
* 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(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry,
wait_bit_action_f *action, unsigned mode)
{
int ret = 0;
do {
prepare_to_wait(wq_head, &wbq_entry->wq_entry, mode);
if (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags))
ret = (*action)(&wbq_entry->key, mode);
} while (test_bit_acquire(wbq_entry->key.bit_nr, wbq_entry->key.flags) && !ret);
finish_wait(wq_head, &wbq_entry->wq_entry);
return ret;
}
EXPORT_SYMBOL(__wait_on_bit);
int __sched out_of_line_wait_on_bit(void *word, int bit,
wait_bit_action_f *action, unsigned mode)
{
struct wait_queue_head *wq_head = bit_waitqueue(word, bit);
DEFINE_WAIT_BIT(wq_entry, word, bit);
return __wait_on_bit(wq_head, &wq_entry, 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)
{
struct wait_queue_head *wq_head = bit_waitqueue(word, bit);
DEFINE_WAIT_BIT(wq_entry, word, bit);
wq_entry.key.timeout = jiffies + timeout;
return __wait_on_bit(wq_head, &wq_entry, action, mode);
}
EXPORT_SYMBOL_GPL(out_of_line_wait_on_bit_timeout);
int __sched
__wait_on_bit_lock(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry,
wait_bit_action_f *action, unsigned mode)
{
int ret = 0;
for (;;) {
prepare_to_wait_exclusive(wq_head, &wbq_entry->wq_entry, mode);
if (test_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags)) {
ret = action(&wbq_entry->key, mode);
/*
* See the comment in prepare_to_wait_event().
* finish_wait() does not necessarily takes wwq_head->lock,
* but test_and_set_bit() implies mb() which pairs with
* smp_mb__after_atomic() before wake_up_page().
*/
if (ret)
finish_wait(wq_head, &wbq_entry->wq_entry);
}
if (!test_and_set_bit(wbq_entry->key.bit_nr, wbq_entry->key.flags)) {
if (!ret)
finish_wait(wq_head, &wbq_entry->wq_entry);
return 0;
} else if (ret) {
return ret;
}
}
}
EXPORT_SYMBOL(__wait_on_bit_lock);
int __sched out_of_line_wait_on_bit_lock(void *word, int bit,
wait_bit_action_f *action, unsigned mode)
{
struct wait_queue_head *wq_head = bit_waitqueue(word, bit);
DEFINE_WAIT_BIT(wq_entry, word, bit);
return __wait_on_bit_lock(wq_head, &wq_entry, action, mode);
}
EXPORT_SYMBOL(out_of_line_wait_on_bit_lock);
void __wake_up_bit(struct wait_queue_head *wq_head, void *word, int bit)
{
struct wait_bit_key key = __WAIT_BIT_KEY_INITIALIZER(word, bit);
if (waitqueue_active(wq_head))
__wake_up(wq_head, 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 hash-table'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_atomic(), 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 *__var_waitqueue(void *p)
{
return bit_wait_table + hash_ptr(p, WAIT_TABLE_BITS);
}
EXPORT_SYMBOL(__var_waitqueue);
static int
var_wake_function(struct wait_queue_entry *wq_entry, unsigned int mode,
int sync, void *arg)
{
struct wait_bit_key *key = arg;
struct wait_bit_queue_entry *wbq_entry =
container_of(wq_entry, struct wait_bit_queue_entry, wq_entry);
if (wbq_entry->key.flags != key->flags ||
wbq_entry->key.bit_nr != key->bit_nr)
return 0;
return autoremove_wake_function(wq_entry, mode, sync, key);
}
void init_wait_var_entry(struct wait_bit_queue_entry *wbq_entry, void *var, int flags)
{
*wbq_entry = (struct wait_bit_queue_entry){
.key = {
.flags = (var),
.bit_nr = -1,
},
.wq_entry = {
.flags = flags,
.private = current,
.func = var_wake_function,
.entry = LIST_HEAD_INIT(wbq_entry->wq_entry.entry),
},
};
}
EXPORT_SYMBOL(init_wait_var_entry);
void wake_up_var(void *var)
{
__wake_up_bit(__var_waitqueue(var), var, -1);
}
EXPORT_SYMBOL(wake_up_var);
__sched int bit_wait(struct wait_bit_key *word, int mode)
{
schedule();
if (signal_pending_state(mode, current))
return -EINTR;
return 0;
}
EXPORT_SYMBOL(bit_wait);
__sched int bit_wait_io(struct wait_bit_key *word, int mode)
{
io_schedule();
if (signal_pending_state(mode, current))
return -EINTR;
return 0;
}
EXPORT_SYMBOL(bit_wait_io);
__sched int bit_wait_timeout(struct wait_bit_key *word, int mode)
{
unsigned long now = READ_ONCE(jiffies);
if (time_after_eq(now, word->timeout))
return -EAGAIN;
schedule_timeout(word->timeout - now);
if (signal_pending_state(mode, current))
return -EINTR;
return 0;
}
EXPORT_SYMBOL_GPL(bit_wait_timeout);
__sched int bit_wait_io_timeout(struct wait_bit_key *word, int mode)
{
unsigned long now = READ_ONCE(jiffies);
if (time_after_eq(now, word->timeout))
return -EAGAIN;
io_schedule_timeout(word->timeout - now);
if (signal_pending_state(mode, current))
return -EINTR;
return 0;
}
EXPORT_SYMBOL_GPL(bit_wait_io_timeout);
void __init wait_bit_init(void)
{
int i;
for (i = 0; i < WAIT_TABLE_SIZE; i++)
init_waitqueue_head(bit_wait_table + i);
}
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