Deadlock characterization(死锁的特性) Deadlock can arise if four conditions hold simultaneously (四个条件同时出现,死锁将会发生 Mutual exclusion: only one process at a time can use a resource. 互斥:一次只有一个进程可以使用一个资源) Hold and wait: a process holding at least one resource is waiting to acquire additional resources held by other processes (占有并等待:一个至少持有一个资源的进程等待获得额外的由其他进程 所持有的资源) No preemption: a resource can be released only voluntarily by the process holding it, after that process has completed its task. (不可抢占:一个资源只有当持有它的进程完成任务后,自由的释放 Circular wait: there exists a set (Po, P1,..., Po] of waiting processes such that Po is waiting for a resource that is held by P1, P, is waiting for a resource that is held by P2,..., Pn-1 is waiting for a resource that is held by Pns and Po is waiting for a resource that is held by p。(循环等待:等待资源的进程之间存在环) Applied Operating System Concepts 8.5 Silberschatz, GalVin, and Gagne@1999Silberschatz ,Galvin, and Gagne©1999 8.5 Applied Operating System Concepts Deadlock Characterization（死锁的特性） • Mutual exclusion: only one process at a time can use a resource.（ 互斥：一次只有一个进程可以使用一个资源） • Hold and wait: a process holding at least one resource is waiting to acquire additional resources held by other processes. （占有并等待：一个至少持有一个资源的进程等待获得额外的由其他进程 所持有的资源） • No preemption: a resource can be released only voluntarily by the process holding it, after that process has completed its task. （不可抢占：一个资源只有当持有它的进程完成任务后，自由的释放） • Circular wait: there exists a set {P0 , P1 , …, P0} of waiting processes such that P0 is waiting for a resource that is held by P1 , P1 is waiting for a resource that is held by P2 , …, Pn–1 is waiting for a resource that is held by Pn, and P0 is waiting for a resource that is held by P0 .（循环等待：等待资源的进程之间存在环） Deadlock can arise if four conditions hold simultaneously. （四个条件同时出现，死锁将会发生）