diff --git a/bitbake/lib/bb/cooker.py b/bitbake/lib/bb/cooker.py
index f79dc2770d..c0a7a2fd79 100644
--- a/bitbake/lib/bb/cooker.py
+++ b/bitbake/lib/bb/cooker.py
@@ -1717,6 +1717,7 @@ class BBCooker:
     def post_serve(self):
         self.shutdown(force=True)
         prserv.serv.auto_shutdown()
+        bb.parse.siggen.exit()
         if self.hashserv:
             self.hashserv.process.terminate()
             self.hashserv.process.join()
diff --git a/bitbake/lib/bb/siggen.py b/bitbake/lib/bb/siggen.py
index 96e16a45f8..ff6b24ccda 100644
--- a/bitbake/lib/bb/siggen.py
+++ b/bitbake/lib/bb/siggen.py
@@ -156,6 +156,9 @@ class SignatureGenerator(object):
 
         return DataCacheProxy()
 
+    def exit(self):
+        return
+
 class SignatureGeneratorBasic(SignatureGenerator):
     """
     """
@@ -489,6 +492,12 @@ class SignatureGeneratorUniHashMixIn(object):
             self._client = hashserv.create_client(self.server)
         return self._client
 
+    def exit(self):
+        if getattr(self, '_client', None) is not None:
+            self._client.close()
+            self._client = None
+        return super().exit()
+
     def get_stampfile_hash(self, tid):
         if tid in self.taskhash:
             # If a unique hash is reported, use it as the stampfile hash. This