Add a test case to catch the failure

src/python/grpcio_tests/tests/tests.json

@@ -50,6 +50,7 @@
   "unit._empty_message_test.EmptyMessageTest",
   "unit._error_message_encoding_test.ErrorMessageEncodingTest",
   "unit._exit_test.ExitTest",
+  "unit._grpc_shutdown_test.GrpcShutdownTest",
   "unit._interceptor_test.InterceptorTest",
   "unit._invalid_metadata_test.InvalidMetadataTest",
   "unit._invocation_defects_test.InvocationDefectsTest",

src/python/grpcio_tests/tests/unit/BUILD.bazel

@@ -18,6 +18,7 @@ GRPCIO_TESTS_UNIT = [
     "_empty_message_test.py",
     "_error_message_encoding_test.py",
     "_exit_test.py",
+    "_grpc_shutdown_test.py",
     "_interceptor_test.py",
     "_invalid_metadata_test.py",
     "_invocation_defects_test.py",

src/python/grpcio_tests/tests/unit/_grpc_shutdown_test.py

@@ -0,0 +1,54 @@
+# Copyright 2019 The gRPC Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Tests the gRPC Core shutdown path."""
+
+import time
+import threading
+import unittest
+import datetime
+
+import grpc
+
+_TIMEOUT_FOR_SEGFAULT = datetime.timedelta(seconds=10)
+
+
+class GrpcShutdownTest(unittest.TestCase):
+
+    def test_channel_close_with_connectivity_watcher(self):
+        """Originated by https://github.com/grpc/grpc/issues/20299.
+        
+        The grpc_shutdown happens synchronously, but there might be Core object
+        references left in Cython which might lead to ABORT or SIGSEGV.
+        """
+        connection_failed = threading.Event()
+
+        def on_state_change(state):
+            if state in (grpc.ChannelConnectivity.TRANSIENT_FAILURE,
+                         grpc.ChannelConnectivity.SHUTDOWN):
+                connection_failed.set()
+
+        # Connects to an void address, and subscribes state changes
+        channel = grpc.insecure_channel("0.1.1.1:12345")
+        channel.subscribe(on_state_change, True)
+
+        deadline = datetime.datetime.now() + _TIMEOUT_FOR_SEGFAULT
+
+        while datetime.datetime.now() < deadline:
+            time.sleep(0.1)
+            if connection_failed.is_set():
+                channel.close()
+
+
+if __name__ == '__main__':
+    unittest.main(verbosity=2)