From 6d0349637290600b2b64a99ea183667106f3dd27 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Thu, 21 May 2020 03:27:40 -0500
Subject: [PATCH] Ensure storage write consume the data under the lock (#35889)

If two writes trigger at the same time the data would already
be consumed.
---
 homeassistant/helpers/storage.py | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/homeassistant/helpers/storage.py b/homeassistant/helpers/storage.py
index b5ac942bf2f..d2b4c334937 100644
--- a/homeassistant/helpers/storage.py
+++ b/homeassistant/helpers/storage.py
@@ -200,14 +200,19 @@ class Store:
 
     async def _async_handle_write_data(self, *_args):
         """Handle writing the config."""
-        data = self._data
-
-        if "data_func" in data:
-            data["data"] = data.pop("data_func")()
-
-        self._data = None
 
         async with self._write_lock:
+            if self._data is None:
+                # Another write already consumed the data
+                return
+
+            data = self._data
+
+            if "data_func" in data:
+                data["data"] = data.pop("data_func")()
+
+            self._data = None
+
             try:
                 await self.hass.async_add_executor_job(
                     self._write_data, self.path, data