While it is hard to resolve a deadlock which has been detected, fortunately it is fairly easy to prevent deadlocks from ever happening. The key is that the conditions above for deadlock are all necessary. We just have to ensure that at least one condition cannot be true. We de?nitely cannot get rid of the problem of ?nite resources; that is something we have to live with. And in many cases it can be dif?cult to get rid of the conditions of hold-and-wait and lack of preemption.
But we can eliminate circular waiting. One standard way of doing this is to have a so-called canonical ordering of the locks. This means that the programmer must always acquire the locks in a speci?ed order, such as ?rst lock1, then lock2, then lock3, etc. By doing so, we will ensure a system whose thread/resource graph is cycle-free, and therefore the system will be deadlock-free.