Yufeng He 2e789eae18
fix(skills): synchronize skill storage singleton lifecycle (#3778)
get_or_new_skill_storage() and reset_skill_storage() touch the
process-global skill storage singleton without a lock - the same
unsynchronized check-then-create that #3730 just fixed in
sandbox_provider.py, the module this file documents itself as mirroring.

Two callers racing a cold start can both see _default_skill_storage is
None and each build a SkillStorage, so the second overwrites the first;
a reset_skill_storage() racing a get can also null the global between
the None-check and the return.

Guard the build/return and the reset with a module-level threading.Lock
and a double check, mirroring get_memory_storage(). Construction stays
inside the lock (rather than sandbox_provider's build-outside-then-
discard-the-loser) because SkillStorage has no teardown hook, so a
losing racer's orphan could not be cleaned up.

Add backend/tests/test_skill_storage_lifecycle.py with concurrency
regression tests (8-thread cold-start race asserting a single instance;
reset racing gets asserting no None is returned).

Signed-off-by: Yufeng He <40085740+he-yufeng@users.noreply.github.com>
2026-06-25 23:18:57 +08:00
..