wakeup.c

/*
 * Wake up waiters matching bitset queued on this futex (uaddr).
 */
static int futex_wake(u32 __user *uaddr, unsigned int flags, int nr_wake, u32 bitset)
{
	struct futex_hash_bucket *hb;
	struct futex_q *this, *next;
	union futex_key key = FUTEX_KEY_INIT;
	int ret;
	DEFINE_WAKE_Q(wake_q);

	if (!bitset)
		return -EINVAL;

	ret = get_futex_key(uaddr, flags & FLAGS_SHARED, &key, FUTEX_READ);
	if (unlikely(ret != 0))
		goto out;

	hb = hash_futex(&key);

	/* Make sure we really have tasks to wakeup */
	if (!hb_waiters_pending(hb))
		goto out_put_key;

	spin_lock(&hb->lock);

        // plist_for_each_entry_safe: mark_wake_futex the matching futex
        // ...

	spin_unlock(&hb->lock);
	wake_up_q(&wake_q);
out_put_key:
	put_futex_key(&key);
out:
	return ret;
}