static int ep_remove(struct eventpoll *ep, struct epitem *epi)
{
	unsigned long flags;
	struct file *file = epi->ffd.file;

	/*
	 * Removes poll wait queue hooks. We _have_ to do this without holding
	 * the "ep->lock" otherwise a deadlock might occur. This because of the
	 * sequence of the lock acquisition. Here we do "ep->lock" then the wait
	 * queue head lock when unregistering the wait queue. The wakeup callback
	 * will run by holding the wait queue head lock and will call our callback
	 * that will try to get "ep->lock".
	 */
	ep_unregister_pollwait(ep, epi);

	/* Remove the current item from the list of epoll hooks */
	spin_lock(&file->f_lock);
	if (ep_is_linked(&epi->fllink))
		list_del_init(&epi->fllink);
	spin_unlock(&file->f_lock);

	rb_erase(&epi->rbn, &ep->rbr);

	spin_lock_irqsave(&ep->lock, flags);
	if (ep_is_linked(&epi->rdllink))
		list_del_init(&epi->rdllink);
	spin_unlock_irqrestore(&ep->lock, flags);

	/* At this point it is safe to free the eventpoll item */
	kmem_cache_free(epi_cache, epi);

	atomic_long_dec(&ep->user->epoll_watches);

	return 0;
}

Unknown