How is deadlock handled in Unix?

Answer 1

A deadlock situation can arise if and only if the following four conditions hold simultaneously in a system-

Mutual Exclusion: At least one resource is held in a non-sharable mode that is only one process at a time can use the resource. If another process requests that resource, the requesting process must be delayed until the resource has been released.

Hold and Wait:There must exist a process that is holding at least one resource and is waiting to acquire additional resources that are currently being held by other processes.

No Preemption: Resouces cannot be preempted; that is, a resource can only be released voluntarily by the process holding it, after the process has completed its task.

Circular Wait: There must exist a set {p0, p1,.....pn} of waiting processes such that p0 is waiting for a resource which is held by p1, p1 is waiting for a resource which is held by p2,..., pn-1 is waiting for a resource which is held by pn and pn is waiting for a resource which is held by p0.

Answer 2

You don't mention what type or kind of deadlock you are interested in, and there can be several types. In any case, the discussion of such as complex topic is too complicated to explain here. You should consult an Operating Systems textbook for in depth answers to questions such as this.