User-Mode Event Flags for Low-Overhead Processor Event Handling
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Solution Overview
Problem
Handling events in processor cores, such as exceptions and interrupts, often disrupts the normal flow of execution, leading to time-consuming processes when event handlers are launched, particularly for user tasks.
Innovation Solution
Implementing an event flag mask register and an event flag register, where a supervisor task can disable events and allow user tasks to poll the event flag register to determine completion of data operations without immediate event handling, reducing overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an event handler is immediately launched when an event occurs, then the event is handled promptly, but the normal flow of execution is disrupted and time is lost
Solution Approach 1:
The patent extracts the event handling process from the critical execution path by introducing an event flag register that captures events without immediately interrupting the task. The event is recorded in the flag register, and the task can later check the flag at convenient points without being forced to pause execution, thus removing the time-critical interruption while preserving event information.
Solution Approach 2:
The event flag register serves as an intermediary between event sources and task execution. Instead of directly interrupting task execution when an event occurs, the system uses the flag register as a buffer that records events for later processing, allowing the task to continue uninterrupted while still capturing event information for subsequent handling.
2Reliability
If a supervisor task manages event flags, then secure event management is ensured, but additional overhead is introduced
Solution Approach 1:
The patent applies local quality by differentiating access rights to different parts of the event management system. Supervisor tasks have full access to assert and clear event flags, while user tasks have restricted access to only read event flags. This localized differentiation of permissions ensures security for critical operations while allowing broader access for non-critical operations, reducing overall system complexity.
3Productivity
If user tasks can clear event flags, then event processing is streamlined, but security risks increase
Solution Approach 1:
The patent implements local quality by granting user tasks only read access to event flags while reserving write access (assert and clear operations) exclusively for supervisor tasks. This localized permission structure allows user tasks to efficiently monitor events by reading flags without compromising security by allowing them to modify flag states, thus maintaining both productivity and reliability.
Data Source
AI summary
A method includes asserting a field of an event flag mask register configured to inhibit an event handler. The method also includes, responsive to an event that corresponds to the field of the event flag mask register being triggered: asserting a field of an event flag register associated with the event; and based the field in the event flag register being asserted, taking an action by a task being executed by the data processor core.