int snd_card_disconnect(struct snd_card *card)
{
	struct snd_monitor_file *mfile;
	int err;

	if (!card)
		return -EINVAL;

	spin_lock(&card->files_lock);
	if (card->shutdown) {
		spin_unlock(&card->files_lock);
		return 0;
	}
	card->shutdown = 1;
	spin_unlock(&card->files_lock);

	/* phase 1: disable fops (user space) operations for ALSA API */
	mutex_lock(&snd_card_mutex);
	snd_cards[card->number] = NULL;
	clear_bit(card->number, snd_cards_lock);
	mutex_unlock(&snd_card_mutex);
	
	/* phase 2: replace file->f_op with special dummy operations */
	
	spin_lock(&card->files_lock);
	list_for_each_entry(mfile, &card->files_list, list) {
		/* it's critical part, use endless loop */
		/* we have no room to fail */
		mfile->disconnected_f_op = mfile->file->f_op;

		spin_lock(&shutdown_lock);
		list_add(&mfile->shutdown_list, &shutdown_files);
		spin_unlock(&shutdown_lock);

		mfile->file->f_op = &snd_shutdown_f_ops;
		fops_get(mfile->file->f_op);
	}
	spin_unlock(&card->files_lock);	

	/* phase 3: notify all connected devices about disconnection */
	/* at this point, they cannot respond to any calls except release() */

#if IS_ENABLED(CONFIG_SND_MIXER_OSS)
	if (snd_mixer_oss_notify_callback)
		snd_mixer_oss_notify_callback(card, SND_MIXER_OSS_NOTIFY_DISCONNECT);
#endif

	/* notify all devices that we are disconnected */
	err = snd_device_disconnect_all(card);
	if (err < 0)
		dev_err(card->dev, "not all devices for card %i can be disconnected\n", card->number);

	snd_info_card_disconnect(card);
	if (card->registered) {
		device_del(&card->card_dev);
		card->registered = false;
	}
#ifdef CONFIG_PM
	wake_up(&card->power_sleep);
#endif
	return 0;	
}

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.