add locking around thread-critical sections

invokeai/backend/model_manager/load/model_cache/model_cache_default.py

@@ -20,6 +20,7 @@ context. Use like this:
 
 import gc
 import sys
+import threading
 from contextlib import suppress
 from logging import Logger
 from threading import BoundedSemaphore, Lock
@@ -80,6 +81,7 @@ class ModelCache(ModelCacheBase[AnyModel]):
         self._max_cache_size: float = max_cache_size
         self._execution_devices: Set[torch.device] = execution_devices or self._get_execution_devices()
         self._storage_device: torch.device = storage_device
+        self._lock = threading.Lock()
         self._logger = logger or InvokeAILogger.get_logger(self.__class__.__name__)
         self._log_memory_usage = log_memory_usage
         self._stats: Optional[CacheStats] = None
@@ -162,6 +164,7 @@ class ModelCache(ModelCacheBase[AnyModel]):
         submodel_type: Optional[SubModelType] = None,
     ) -> None:
         """Store model under key and optional submodel_type."""
+        with self._lock:
             key = self._make_cache_key(key, submodel_type)
             assert key not in self._cached_models
 
@@ -185,6 +188,7 @@ class ModelCache(ModelCacheBase[AnyModel]):
 
         This may raise an IndexError if the model is not in the cache.
         """
+        with self._lock:
             key = self._make_cache_key(key, submodel_type)
             if key in self._cached_models:
                 if self.stats: