rust-concurrency_skill

Overview

This skill is a Rust concurrency and async programming expert that diagnoses, designs, and optimizes concurrent code. It focuses on Send/Sync rules, threads vs async, synchronization primitives (Mutex, RwLock, Arc, atomics), channels, deadlock prevention, and race condition debugging. It helps choose models, apply patterns, and verify thread safety in real projects.

How this skill works

The skill inspects code and design choices to recommend the appropriate concurrency model (threads, async/await, or hybrid). It analyzes types for Send/Sync bounds, suggests synchronization primitives, detects common anti-patterns (locks across await, inconsistent lock ordering), and proposes fixes or refactors. It also generates checks and commands for testing with miri, loom, and sanitizers.

When to use it

• Choosing between threads and async for an I/O- or CPU-bound workload
• Refactoring shared mutable state to remove data races or reduce contention
• Diagnosing compilation errors like E0277 (Send/Sync) and mutex-related panics
• Reviewing code for deadlock risks and lock-ordering violations
• Designing task spawning, timeouts, and cancellation strategies for async systems

Best practices

• Prefer threads (or rayon) for CPU-parallel workloads and async runtimes (tokio/async-std) for I/O-bound tasks
• Use Arc + Mutex/RwLock for shared ownership; replace Rc with Arc for cross-thread use
• Keep lock scopes minimal and never hold MutexGuard across await points
• Establish consistent lock ordering and document it to avoid deadlocks
• Favor atomics for simple counters/flags and message passing for decoupled components

Example use cases

• Convert a blocking HTTP client into async tokio tasks with timeouts and cancellation
• Fix Send/Sync compile errors by identifying non-Send fields and replacing Rc with Arc
• Design a producer/consumer pipeline using mpsc channels to avoid shared-state locks
• Reduce contention on a shared cache by switching to Arc<RwLock<T>> for read-heavy workloads
• Write tests with loom or thread sanitizer to reproduce and fix subtle race conditions