static long snd_timer_user_ioctl(struct file *file, unsigned int cmd,
				 unsigned long arg)
{
	struct snd_timer_user *tu = file->private_data;
	long ret;

	mutex_lock(&tu->ioctl_lock);
	ret = __snd_timer_user_ioctl(file, cmd, arg);
	mutex_unlock(&tu->ioctl_lock);
	return ret;
}
The program contains a code sequence that can run concurrently with other code, and the code sequence 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 that is operating concurrently.