release command semaphore after timeout

bumble/host.py

@@ -692,10 +692,8 @@ async def _send_command(
         finally:
             self.pending_command = None
             self.pending_response = None
-            if (
-                response is not None
-                and response.num_hci_command_packets
-                and self.command_semaphore.locked()
+            if response is None or (
+                response.num_hci_command_packets and self.command_semaphore.locked()
             ):
                 self.command_semaphore.release()
 

tests/host_test.py

@@ -171,14 +171,15 @@ def set_packet_sink(self, sink: TransportSink) -> None:
 
 
 class Sink:
-    response: HCI_Event
+    response: HCI_Event | None
 
-    def __init__(self, source: Source, response: HCI_Event) -> None:
+    def __init__(self, source: Source, response: HCI_Event | None) -> None:
         self.source = source
         self.response = response
 
     def on_packet(self, packet: bytes) -> None:
-        self.source.sink.on_packet(bytes(self.response))
+        if self.response is not None:
+            self.source.sink.on_packet(bytes(self.response))
 
 
 @pytest.mark.asyncio
@@ -228,6 +229,23 @@ async def test_send_sync_command() -> None:
     assert isinstance(response3.return_parameters, HCI_GenericReturnParameters)
 
 
+@pytest.mark.asyncio
+async def test_send_sync_command_timeout() -> None:
+    source = Source()
+    sink = Sink(source, None)
+
+    host = Host(source, sink)
+    host.ready = True
+
+    with pytest.raises(asyncio.TimeoutError):
+        await host.send_sync_command(HCI_Reset_Command(), response_timeout=0.01)
+
+    # The sending semaphore should have been released, so this should not block
+    # indefinitely
+    with pytest.raises(asyncio.TimeoutError):
+        await host.send_sync_command(hci.HCI_Reset_Command(), response_timeout=0.01)
+
+
 @pytest.mark.asyncio
 async def test_send_async_command() -> None:
     source = Source()