CSC/ECE 506 Spring 2011/ch11 BB EP: Difference between revisions
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== Race Conditions == | == Race Conditions == | ||
In a distributed shared memory system with caching, the emergence of race conditions is extremely likely. This is mainly due to the lack of a bus for serialization of actions. It is further compounded by the problem of network errors and congestion. | |||
The early invalidation case from Section 11.4 in Solihin is an excellent example of a race condition that can arise in a distributed system. Recall the diagram from the text, and the cache coherence actions. | |||
1. A sends a read request to home. | |||
2. Home replies with data (but the message gets delayed). | |||
3. B sends a write request to home. | |||
4. Home sends invalidation to A, and it arrives before the ReplyD | |||
=== Prevention in the SCI Protocol === | |||
Race conditions are almost non-existent in the SCI protocol, due primarily to the protocol's design. | |||
==== Head Node ==== | |||
==== Memory Access ==== | |||
==== Atomic Transactions ==== | |||
=== Possible Race Conditions === | |||
==== Communication Delays ==== | |||
==== Concurrent List Deletions ==== | |||
==== Simultaneous Deletion and Invalidation ==== | |||
== Summary == | == Summary == | ||
Revision as of 01:35, 18 April 2011
History
Background
State Diagrams
Memory
Processors
Race Conditions
In a distributed shared memory system with caching, the emergence of race conditions is extremely likely. This is mainly due to the lack of a bus for serialization of actions. It is further compounded by the problem of network errors and congestion.
The early invalidation case from Section 11.4 in Solihin is an excellent example of a race condition that can arise in a distributed system. Recall the diagram from the text, and the cache coherence actions.
1. A sends a read request to home. 2. Home replies with data (but the message gets delayed). 3. B sends a write request to home. 4. Home sends invalidation to A, and it arrives before the ReplyD
Prevention in the SCI Protocol
Race conditions are almost non-existent in the SCI protocol, due primarily to the protocol's design.