Bài giảng Hệ điều hành nâng cao - Chapter 18: Distributed Coordination giúp bạn đọc nắm được quá trình phối hợp phân phối, thứ tự sự kiện, số nguyên tử số, các thuật toán,.Đây là tài liệu tham khảo thuộc chuyên ngành Công nghệ thông tin. | Chapter 18: Distributed Coordination 1 Chapter 18: Distributed Coordination Event Ordering Mutual Exclusion Atomicity Concurrency Control Deadlock Handling Election Algorithms Reaching Agreement 2 Chapter Objectives To describe various methods for achieving mutual exclusion in a distributed system To explain how atomic transactions can be implemented in a distributed system To show how some of the concurrency-control schemes discussed in Chapter 6 can be modified for use in a distributed environment To present schemes for handling deadlock prevention, deadlock avoidance, and deadlock detection in a distributed system 3 Event Ordering Happened-before relation (denoted by ) If A and B are events in the same process, and A was executed before B, then A B If A is the event of sending a message by one process and B is the event of receiving that message by another process, then A B If A B and B C then A C 4 Relative Time for Three Concurrent Processes 5 Implementation of Associate a timestamp with each system event Require that for every pair of events A and B, if A B, then the timestamp of A is less than the timestamp of B Within each process Pi a logical clock, LCi is associated The logical clock can be implemented as a simple counter that is incremented between any two successive events executed within a process Logical clock is monotonically increasing A process advances its logical clock when it receives a message whose timestamp is greater than the current value of its logical clock If the timestamps of two events A and B are the same, then the events are concurrent We may use the process identity numbers to break ties and to create a total ordering 6 Distributed Mutual Exclusion (DME) Assumptions The system consists of n processes; each process Pi resides at a different processor Each process has a critical section that requires mutual exclusion Requirement If Pi is executing in its critical section, then no other process Pj is executing in its . | Chapter 18: Distributed Coordination 1 Chapter 18: Distributed Coordination Event Ordering Mutual Exclusion Atomicity Concurrency Control Deadlock Handling Election Algorithms Reaching Agreement 2 Chapter Objectives To describe various methods for achieving mutual exclusion in a distributed system To explain how atomic transactions can be implemented in a distributed system To show how some of the concurrency-control schemes discussed in Chapter 6 can be modified for use in a distributed environment To present schemes for handling deadlock prevention, deadlock avoidance, and deadlock detection in a distributed system 3 Event Ordering Happened-before relation (denoted by ) If A and B are events in the same process, and A was executed before B, then A B If A is the event of sending a message by one process and B is the event of receiving that message by another process, then A B If A B and B C then A C 4 Relative Time for Three Concurrent Processes 5 Implementation of .
