Siphons can be used to characterise deadlock states and solve deadlock problems in Petri nets that model flexible manufacturing systems. This article presents a novel deadlock prevention policy for Petri nets using siphon extraction. At each iteration, a siphon extraction algorithm finds a maximal deadly marked siphon, classifies the places in it, and decides a necessary siphon from the classified places. Accordingly, the deadlock prevention policy adds a proper control place (CP) to make each necessary siphon marked or max-controlled until the controlled system is live. By adopting the classification of places, deciding necessary siphons, and adding the proper CPs, the proposed deadlock prevention policy avoids a complete siphon enumeration, adds a small number of CPs, and leads to a liveness-enforcing supervisor with a simple structure compared with closely related approaches in the literature. Finally, a case study shows its appealing behavioural permissiveness.