Hardware Transactional Execution Abort Processing
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Solution Overview
Problem
In multiprocessor programming, updating multiple storage locations simultaneously by multiple CPUs is challenging due to the need for serialization, which often results in coarse-grained locking, leading to potential deadlocks and recovery issues, and existing mechanisms are costly and complex to manage exception conditions.
Innovation Solution
A computer program product that facilitates transactional execution by using a TRANSACTION BEGIN instruction to enter a transactional execution mode, allowing for atomic updates of multiple storage locations, with optional nested transactions and controlled register saving, and provides mechanisms for aborting transactions to manage exceptions efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coarse-grained locking is used to serialize access to multiple storage locations, then safety of concurrent updates is improved, but productivity deteriorates due to serialization overhead and potential deadlocks
Solution Approach 1:
The patent segments the locking mechanism into fine-grained locks associated with individual storage locations rather than using a single coarse-grained lock for all locations. This allows concurrent access to different storage locations while maintaining safety, thereby improving productivity without sacrificing reliability
Solution Approach 2:
The patent introduces a transaction manager as an intermediary that coordinates access to multiple storage locations without requiring traditional locks. The transaction manager enables optimistic concurrency control, allowing multiple CPUs to access storage locations simultaneously while ensuring eventual consistency, thus improving both productivity and reliability
2Productivity
If fine-grained serialization is implemented using multiple lock points, then productivity is improved by reducing serialization scope, but device complexity increases due to lock hierarchy management
Solution Approach 1:
The patent extracts the locking logic from the application program and relocates it to the hardware transaction manager. This eliminates the need for application programs to manage complex lock hierarchies, reducing device complexity while maintaining fine-grained concurrent access capabilities
Solution Approach 2:
The transaction manager provides self-service by automatically managing transaction coordination, conflict detection, and resolution without requiring external lock management. This simplifies the system architecture while enabling fine-grained concurrent access, improving productivity without increasing complexity
3Reliability
If traditional exception handling is used in multiprocessor environments, then reliability is improved through error interception, but device complexity increases due to recovery environment setup
Solution Approach 1:
The transaction manager acts as an intermediary that provides built-in exception handling and rollback capabilities. When an error occurs during transactional execution, the transaction manager automatically intercepts the exception and rolls back the transaction, providing reliability without requiring complex external recovery environments
Data Source
AI summary
A transaction executing within a computing environment ends prior to completion; i.e., execution is aborted. Pursuant to aborting execution, a hardware transactional execution CPU mode is exited, and one or more of the following is performed: restoring selected registers; committing nontransactional stores on abort; branching to a transaction abort program status word specified location; setting a condition code and/or abort code; and/or preserving diagnostic information.