Increase lock scope in ModuleCache.refresh

tests/link/c/test_cmodule.py

@@ -5,6 +5,7 @@ But this one tests a current behavior that isn't good: the c_code isn't
 deterministic based on the input type and the op.
 """
 import logging
+import multiprocessing
 import os
 import tempfile
 from unittest.mock import patch
@@ -12,6 +13,8 @@ from unittest.mock import patch
 import numpy as np
 import pytest
 
+import aesara
+import aesara.tensor as at
 from aesara.compile.function import function
 from aesara.compile.ops import DeepCopyOp
 from aesara.configdefaults import config
@@ -139,3 +142,47 @@ def test_linking_patch(listdir_mock, platform):
                 "-lmkl_core",
                 "-lmkl_rt",
             ]
+
+
+def test_cache_race_condition():
+
+    with tempfile.TemporaryDirectory() as dir_name:
+
+        @config.change_flags(on_opt_error="raise", on_shape_error="raise")
+        def f_build(factor):
+            # Some of the caching issues arise during constant folding within the
+            # optimization passes, so we need these config changes to prevent the
+            # exceptions from being caught
+            a = at.vector()
+            f = aesara.function([a], factor * a)
+            return f(np.array([1], dtype=config.floatX))
+
+        ctx = multiprocessing.get_context()
+        compiledir_prop = aesara.config._config_var_dict["compiledir"]
+
+        # The module cache must (initially) be `None` for all processes so that
+        # `ModuleCache.refresh` is called
+        with patch.object(compiledir_prop, "val", dir_name, create=True), patch.object(
+            aesara.link.c.cmodule, "_module_cache", None
+        ):
+
+            assert aesara.config.compiledir == dir_name
+
+            num_procs = 30
+            rng = np.random.default_rng(209)
+
+            for i in range(10):
+                # A random, constant input to prevent caching between runs
+                factor = rng.random()
+                procs = [
+                    ctx.Process(target=f_build, args=(factor,))
+                    for i in range(num_procs)
+                ]
+                for proc in procs:
+                    proc.start()
+                for proc in procs:
+                    proc.join()
+
+                assert not any(
+                    exit_code != 0 for exit_code in [proc.exitcode for proc in procs]
+                )