/* * The implementation of the wait_bit*() and related waiting APIs: */#include <linux/wait_bit.h>#include <linux/sched/signal.h>#include <linux/sched/debug.h>#include <linux/hash.h> #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;	else		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(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); /* * Manipulate the atomic_t address to produce a better bit waitqueue table hash * index (we're keying off bit -1, but that would produce a horrible hash * value). */static inline wait_queue_head_t *atomic_t_waitqueue(atomic_t *p){	if (BITS_PER_LONG == 64) {		unsigned long q = (unsigned long)p;		return bit_waitqueue((void *)(q & ~1), q & 1);	}	return bit_waitqueue(p, 0);} static int wake_atomic_t_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);	atomic_t *val = key->flags; 	if (wait_bit->key.flags != key->flags ||	    wait_bit->key.bit_nr != key->bit_nr ||	    atomic_read(val) != 0)		return 0;	return autoremove_wake_function(wq_entry, mode, sync, key);} /* * To allow interruptible waiting and asynchronous (i.e. nonblocking) waiting, * the actions of __wait_on_atomic_t() are permitted return codes.  Nonzero * return codes halt waiting and return. */static __schedint __wait_on_atomic_t(struct wait_queue_head *wq_head, struct wait_bit_queue_entry *wbq_entry,		       int (*action)(atomic_t *), unsigned mode){	atomic_t *val;	int ret = 0; 	do {		prepare_to_wait(wq_head, &wbq_entry->wq_entry, mode);		val = wbq_entry->key.flags;		if (atomic_read(val) == 0)			break;		ret = (*action)(val);	} while (!ret && atomic_read(val) != 0);	finish_wait(wq_head, &wbq_entry->wq_entry);	return ret;} #define DEFINE_WAIT_ATOMIC_T(name, p)					\	struct wait_bit_queue_entry name = {				\		.key = __WAIT_ATOMIC_T_KEY_INITIALIZER(p),		\		.wq_entry = {						\			.private	= current,			\			.func		= wake_atomic_t_function,	\			.entry		=				\				LIST_HEAD_INIT((name).wq_entry.entry),	\		},							\	} __sched int out_of_line_wait_on_atomic_t(atomic_t *p, int (*action)(atomic_t *),					 unsigned mode){	struct wait_queue_head *wq_head = atomic_t_waitqueue(p);	DEFINE_WAIT_ATOMIC_T(wq_entry, p); 	return __wait_on_atomic_t(wq_head, &wq_entry, action, mode);}EXPORT_SYMBOL(out_of_line_wait_on_atomic_t); /** * wake_up_atomic_t - Wake up a waiter on a atomic_t * @p: The atomic_t being waited on, a kernel virtual address * * Wake up anyone waiting for the atomic_t to go to zero. * * Abuse the bit-waker function and its waitqueue hash table set (the atomic_t * check is done by the waiter's wake function, not the by the waker itself). */void wake_up_atomic_t(atomic_t *p){	__wake_up_bit(atomic_t_waitqueue(p), p, WAIT_ATOMIC_T_BIT_NR);}EXPORT_SYMBOL(wake_up_atomic_t); __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);}