From 2df15360fd61ac282fe6e93a9cb992b10a821c5a Mon Sep 17 00:00:00 2001
From: Paulus Schoutsen <balloob@gmail.com>
Date: Thu, 29 Nov 2018 21:00:05 +0100
Subject: [PATCH] Fix race condition in group.set

---
 homeassistant/components/group/__init__.py |  9 ++++++++-
 tests/helpers/test_entity_component.py     | 21 +++++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/homeassistant/components/group/__init__.py b/homeassistant/components/group/__init__.py
index 4dd3571e69c2a6..15a3816c559e83 100644
--- a/homeassistant/components/group/__init__.py
+++ b/homeassistant/components/group/__init__.py
@@ -207,6 +207,13 @@ async def reload_service_handler(service):
         DOMAIN, SERVICE_RELOAD, reload_service_handler,
         schema=RELOAD_SERVICE_SCHEMA)
 
+    service_lock = asyncio.Lock()
+
+    async def locked_service_handler(service):
+        """Handle a service with an async lock."""
+        async with service_lock:
+            await groups_service_handler(service)
+
     async def groups_service_handler(service):
         """Handle dynamic group service functions."""
         object_id = service.data[ATTR_OBJECT_ID]
@@ -284,7 +291,7 @@ async def groups_service_handler(service):
             await component.async_remove_entity(entity_id)
 
     hass.services.async_register(
-        DOMAIN, SERVICE_SET, groups_service_handler,
+        DOMAIN, SERVICE_SET, locked_service_handler,
         schema=SET_SERVICE_SCHEMA)
 
     hass.services.async_register(
diff --git a/tests/helpers/test_entity_component.py b/tests/helpers/test_entity_component.py
index 2bef8c0b53e5cc..7562a38d268e7a 100644
--- a/tests/helpers/test_entity_component.py
+++ b/tests/helpers/test_entity_component.py
@@ -431,3 +431,24 @@ async def test_update_entity(hass):
 
     assert len(entity.async_update_ha_state.mock_calls) == 2
     assert entity.async_update_ha_state.mock_calls[-1][1][0] is True
+
+
+async def test_set_service_race(hass):
+    """Test race condition on setting service."""
+    exception = False
+
+    def async_loop_exception_handler(_, _2) -> None:
+        """Handle all exception inside the core loop."""
+        nonlocal exception
+        exception = True
+
+    hass.loop.set_exception_handler(async_loop_exception_handler)
+
+    await async_setup_component(hass, 'group', {})
+    component = EntityComponent(_LOGGER, DOMAIN, hass, group_name='yo')
+
+    for i in range(2):
+        hass.async_create_task(component.async_add_entities([MockEntity()]))
+
+    await hass.async_block_till_done()
+    assert not exception