操作系统（六）DeadLock

一、概念

A set of processes is deadlocked if each process in the set is waiting for an event that only another process in the set can cause.

二、4个必要条件

• Mutual exclusion condition（互斥执行）
  ? Each resource is either currently assigned to exactly one process or is available.

• Hold and wait condition（保持和等待）
  ? process holding resources can request additional

• No preemption condition（非抢占式）
  ? previously granted resources cannot forcibly taken away

• Circular wait condition（循环等待）
  ? must be a circular chain of 2 or more processes
  ? each is waiting for resource held by next member of the chain

概念题

• 死锁条件
  Four Conditions for Deadlock: Mutual exclusion ,Hold and wait, No preemption and Circular wait