Week 12 Update: Deadlock Fixes & Code Refinement

Overview

This week we took a step back from feature additions to focus on improving system stability and code quality. Our main focus was resolving a critical deadlock issue that surfaced under high-concurrency workloads, alongside a general code cleanup to improve readability, maintainability, and performance.

Deadlock Bug Fix

We identified and fixed a subtle deadlock that occurred during function invocation processing:

• Root Cause:
  • The deadlock stemmed from a circular wait involving the compute service and the invocation tracking system. In some scenarios, a compute host would wait indefinitely for state updates that were blocked by another component waiting on the same resource.
• Resolution:
  • We refactored the execution flow to ensure that locks are acquired in a consistent order and released promptly after shared state updates.
  • Additional safeguards were added to prevent nested blocking calls and to detect potential starvation scenarios.
• Testing Improvements:
  • A new stress test was added to simulate high concurrency and verify that no deadlocks or livelocks occur under load.

Code Cleanup & Optimization

Alongside the bug fix, we also began a pass through the codebase to simplify logic and improve performance:

• Const References over Copies:
  • Functions now pass large objects (e.g., host state, invocation descriptors) by const& instead of by value to avoid unnecessary copies.
• Simplified Control Flow:
  • Complex branching logic was split into helper functions with descriptive names, making it easier to follow scheduling and execution decisions.
• Comment and Naming Improvements:
  • Better inline documentation and more meaningful variable names were introduced to clarify the purpose of each code segment.
• Compile-Time Optimizations:
  • Unused headers and redundant includes were removed, and some templated utilities were rewritten for better compiler friendliness.

Next Steps

• Code Review Round:
  • Begin a formal review process to identify remaining performance hotspots and design inconsistencies.
• Continue Robustness Testing:
  • Expand tests to include simulated resource starvation, rapid-fire function submissions, and long-running invocations.
• Documentation Update:
  • Update developer-facing documentation to reflect the latest design changes, particularly around thread safety and shared state access patterns.

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This week was a necessary pivot toward system reliability. Fixing the deadlock and tightening up our code puts us in a much better position to move forward with confidence as we begin preparing the system for broader usage and evaluation.