[dwaddle]

Summary

This PR addresses #133 by guarding background memory eviction task creation in zcore.cache.base with a threading.Lock double-checked initialization pattern.

Changes

1. Thread-Safe Eviction Task Scheduling: Added _eviction_lock = threading.Lock() in zcore.cache.base. In _ensure_eviction_task(), the loop check and loop.create_task(_start_eviction_loop(...)) assignment are guarded via with _eviction_lock: with double-checked verification.
2. Synchronized Shutdown in close_cache(): Wrapped _eviction_task retrieval and clearing inside with _eviction_lock: to prevent concurrent threads from scheduling a new task while shutdown is in flight.
3. Regression Tests: Added test_ensure_eviction_task_concurrent_thread_safety in tests/test_cache.py exercising concurrent invocation across 20 threads to guarantee exactly one eviction loop task is spawned.

Verification

• uv run ruff format --check: Passed cleanly.
• uv run ruff check: Passed cleanly.
• uv run --all-extras pytest: 516/516 passed.

Closes #133.

[alialfostovar]

Hi @dwaddle,

Wow, this is an exceptionally clean implementation of the double-checked locking pattern! The test with threading.Barrier(20) is brilliant and ensures rock-solid thread safety.

I was actually touching this area last night, but your approach and test suite are far superior and more robust.

Approving and merging this into release/v0.1.0-rc.3. Thank you for elevating the quality of ZCore! 🚀