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    Repair Lost Wakeup Races

    1

    Repair lost wakeups in condition variables, worker queues, shutdown gates, wait/notify loops, and hand-built events.

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    Repair Lost Wakeup Races

    Repair Lost Wakeup Races

    Example session with this skill installed

    Our C++ worker pool checks queue.empty() before acquiring the condition_variable mutex. A producer can enqueue and notify between that check and wait(), leaving the worker asleep until unrelated work arrives. Shutdown occasionally hangs for the same reason. Repair locally with deterministic barriers and ThreadSanitizer tests. Preserve queue capacity, worker count, and scheduling policy; do not replace the wait with polling.

    • Read your context and instructions
    • Compiled the repair lost wakeup

    Lost-wakeup window found. The worker checks queue state outside the condition mutex, then a producer enqueues and notifies before the worker actually waits. The repair makes the queue predicate authoritative under one lock, waits in a predicate loop, notifies after transition, and validates notify-before-wait and spurious-wake orderings with deterministic barriers.

    Connects securely to your tools. The creator never sees your data.

    What you get

    Prevent workers from sleeping when tasks are pending in the queue.Fix shutdown hangs caused by missed termination signals.Eliminate flaky concurrency tests that depend on arbitrary sleeps.Audit and unify mutex ownership across split-lock state transitions.

    About this skill

    The problem

    Race conditions in multi-threaded code often lead to intermittent hangs where workers sleep despite work being available. These bugs are notoriously difficult to reproduce and often "solved" with fragile sleeps that mask the underlying synchronization failure.

    What it does

    • Identifies lost notifications where signals occur between checking state and entering a wait block.
    • Enforces wait-loop discipline by converting incorrect if checks into robust predicate loops.
    • Audits lock ownership to ensure state predicates and notifications share the same synchronization contract.
    • Removes reliance on notification counting and replaces sleep-based tests with deterministic barriers.
    • Implements observability for waiter counts, transition reasons, and shutdown generations.

    Frameworks & tools

    Works with low-level synchronization primitives including condition variables, monitors, mutexes, latches, and atomic state guards in C++, Java, Go, Rust, and Python.

    Why this beats prompting it yourself

    LLMs often suggest polling or increasing timeouts when faced with deadlocks. This skill follows a rigorous concurrency safety protocol that treats notifications as hints rather than durable events, ensuring the state predicate remains the single source of truth without changing your scheduling policy.

    Use cases

    • Fixing intermittent CI hangs during service shutdown sequences.
    • Resolving worker starvation in custom thread pools or task queues.
    • Stabilizing flaky tests that currently rely on time.Sleep to pass.
    • Standardizing synchronization contracts across legacy multi-threaded modules.

    Known limitations

    Does not modify queue capacity, fairness policies, or worker counts. Requires access to the repository files to build a synchronization register.

    How to install

    Works the same in every agent - Claude, Cursor, Codex, Copilot and 20+ more.

    ~30 seconds
    1. 1

      Download the ZIP

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    2. 2

      Unzip into your skills folder

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    3. 3

      Ask your agent to use it

      Restart the agent if it was already running. It picks the skill up automatically - no config needed.

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    Recently published to Agensi

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    Security scanned

    Verified clean 1 month ago

    • Passed all security checks, Safe to install

    Listed1 month ago

    What's inside

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