Background o The processes are cooperating with each other directly or indirectly. Independent process cannot affect or be affected by the execution of another process Cooperating process can affect or be affected by the execution of another process o Concurrent access(并发访问)to shared data may result in data inconsistency(不-致) for example:printer,shared variables/tables/lists o Maintaining data consistency requires mechanisms to ensure the orderly execution of cooperating processes 口18，走卡11月00 陈话兰xlanchen@ustc.edu.cn http/staff.u0117401 Operating System操作系统原理斐 March29,.20196/57. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Background The processes are cooperating with each other directly or indirectly. ▶ Independent process cannot affect or be affected by the execution of another process ▶ Cooperating process can affect or be affected by the execution of another process Concurrent access (并发访问) to shared data may result in data inconsistency(不一致) ▶ for example: printer, shared variables/tables/lists Maintaining data consistency requires mechanisms to ensure the orderly execution of cooperating processes 陈香兰 xlanchen@ustc.edu.cn http://staff.ustc.edu.cn/~xlanchen (Computer Application Laboratory, CS, USTC @ Hefei Embedded System Laboratory, CS, USTC @ Suzhou) 0117401: Operating System 操作系统原理与设计 March 29, 2019 6 / 57