// 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. 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(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 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_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 intvar_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);}