| name | deadlock-analysis |
| description | Analyze application hangs, thread deadlocks, and circular wait conditions. Do not use for race conditions or infinite loops.
|
| version | 1.1.0 |
| time_saved | Manual: 3–8 hours | With skill: 30–60 minutes |
| license | Proprietary — Personal Use Only |
| category | debugging |
| complexity | Advanced |
| tokens | ~4500 |
| tags | ["deadlock","threading","lock-ordering","concurrency","debugging"] |
| author | vheins |
Skill: Deadlock Analysis
Purpose
Resolve thread deadlocks by analyzing lock order and thread dumps, identifying circular waits, and implementing consistent ordering or granularity fixes.
Input
| Variable | Type | Req | Description |
|---|
tech_stack | string | Yes | e.g., "Java + Spring" |
code | string | Yes | Resource acquisition logic |
thread_dump | string | No | Log of waiting threads |
context | string | Yes | Types, counts, recent changes |
Instructions
- Identification: Confirm circular wait (A holds X waits Y; B holds Y waits X).
- Visualization: Draw ASCII wait-for graph.
- Diagnosis: Explain why current ordering/logic creates the cycle.
- Remediation:
- Enforce global lock ordering.
- Transition to
tryLock with timeouts.
- Reduce lock granularity or use coarse locks.
- Prevention: Document lock hierarchies and convention rules.
- Fallback: If no dump, perform structural analysis and provide capture commands (e.g.,
jstack).
Edge Cases
| Case | Strategy |
|---|
| No Dump | Analyze circular dependencies in code; draw hypothetical resource graphs. |
| DB Deadlock | Check DB logs; adjust isolation levels; reorder DML statements. |
| Livelock | Recommend randomized backoff or retry jitter. |
Deadlock Logic
flowchart TD
A([Start: Deadlock Analysis]) --> B[Parse tech_stack, code, thread_dump, context]
B --> C{Thread dump available?}
C -- No --> D[Analyze code for circular locks]
D --> E[Draw resource graph]
E --> F[Provide thread dump commands]
C -- Yes --> G[Confirm deadlock: Thread A holds X waits Y, Thread B holds Y waits X]
G --> H[Draw Wait-For Graph]
H --> I[Identify lock ordering issue]
I --> J{Deadlock type?}
J -- App locks --> K[Fix: Enforce global lock ordering]
J -- DB deadlock --> L[Check DB log, adjust isolation, reorder DML]
J -- Livelock --> M[Add randomized backoff]
K --> N{Performance allows coarse lock?}
N -- Yes --> O[Use single coarse lock]
N -- No --> P[Use tryLock or reduce granularity]
O & P --> Q[Show before/after code]
Q --> R[Add Prevention Strategy]
R --> S([Output: 5-Section Report])
Examples
Quality Gate
MCP Dependencies
@modelcontextprotocol/server-sequential-thinking: Complex reasoning.
Changelog
| Version | Date | Description |
|---|
| 1.1.0 | 2026-03-20 | Restructured: examples/references separated, added fields |
| 1.0.0 | 2026-03-20 | Initial release |
