static void copy_valid_id_string(struct snd_card *card, const char *src,
				 const char *nid)
{
	char *id = card->id;

	while (*nid && !isalnum(*nid))
		nid++;
	if (isdigit(*nid))
		*id++ = isalpha(*src) ? *src : 'D';
	while (*nid && (size_t)(id - card->id) < sizeof(card->id) - 1) {
		if (isalnum(*nid))
			*id++ = *nid;
		nid++;
	}
	*id = 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.