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Grok Bot+18 agentsRepair Lost Wakeup Races
Repair lost wakeups in condition variables, worker queues, shutdown gates, wait/notify loops, and hand-built events.
$5
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.
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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
ifchecks 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.Sleepto 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 use
Skills on Agensi run inside your AI agent. Copy the prompt, paste it into your agent, and it connects to Agensi and installs this skill for you. If a payment is needed, your agent shows it to you first.
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