static void coroutine_fn virtfs_reset(V9fsPDU *pdu)
{
    V9fsState *s = pdu->s;
    V9fsFidState *fidp;

    /* Free all fids */
    while (s->fid_list) {
        /* Get fid */
        fidp = s->fid_list;
        fidp->ref++;

        /* Clunk fid */
        s->fid_list = fidp->next;
        fidp->clunked = 1;

        put_fid(pdu, fidp);
    }
}

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.