In a classical scheduling problem, we are given a set of n jobs of unit length along with precedence constraints, and the goal is to find a schedule of these jobs on m identical machines that minimizes the makespan. Using the standard 3-field notation, it is known as Pm|prec, p_j=1|Cmax. Settling the complexity of Pm|prec, p_j=1|Cmax even for m=3 machines is, together with Subgraph Isomorphism, among the last two open problems from the book of Garey and Johnson [GJ79] for which the computational complexity remains a mystery. We present an algorithm for this problem that runs in (1+\frac{n}{m})^{O(sqrt{nm})} time. This algorithm is subexponential when m = o(n).