Don't hold the runtime lock while we're importing modules in SerializationContext.

It can cause all kinds of deadlocks, since import operations execute arbitrary
code, which can lock things and then attempt to compile. This can lead to deadlocks.

Author: braxtonmckee

typed_python/SerializationContext.py

@@ -398,7 +398,10 @@ def objectFromName(self, name, allowImport=True):
                     if not allowImport:
                         return None
 
-                    return importlib.import_module(name[9:])
+                # make sure to import outside of the lock
+                # otherwise we can deadlock since importing
+                # may trigger compilation
+                return importlib.import_module(name[9:])
             except ModuleNotFoundError:
                 _badModuleCache.add(name[9:])
                 return None
@@ -425,7 +428,10 @@ def objectFromName(self, name, allowImport=True):
                     if not allowImport:
                         return None
 
-                    module = importlib.import_module(moduleName)
+                # make sure to import outside of the lock
+                # otherwise we can deadlock since importing
+                # may trigger compilation
+            module = importlib.import_module(moduleName)
 
             return getattr(module, objName, None)
         except ModuleNotFoundError: