False deadlock detection in case of exception in run_in_executor

asgiref/sync.py

@@ -452,22 +452,29 @@ async def __call__(self, *args: _P.args, **kwargs: _P.kwargs) -> _R:
         func = context.run
         task_context: List[asyncio.Task[Any]] = []
 
-        # Run the code in the right thread
-        exec_coro = loop.run_in_executor(
-            executor,
-            functools.partial(
-                self.thread_handler,
-                loop,
-                sys.exc_info(),
-                task_context,
-                func,
-                child,
-            ),
-        )
+        try:
+            # Run the code in the right thread
+            exec_coro = loop.run_in_executor(
+                executor,
+                functools.partial(
+                    self.thread_handler,
+                    loop,
+                    sys.exc_info(),
+                    task_context,
+                    func,
+                    child,
+                ),
+            )
+        except Exception:
+            _restore_context(context)
+            self.deadlock_context.set(False)
+            raise
+
         ret: _R
         try:
             ret = await asyncio.shield(exec_coro)
         except asyncio.CancelledError:
+            # catch CancelledError only in await
             cancel_parent = True
             try:
                 task = task_context[0]

tests/test_sync.py

@@ -8,7 +8,7 @@
 from concurrent.futures import ThreadPoolExecutor
 from functools import wraps
 from typing import Any
-from unittest import TestCase
+from unittest import TestCase, mock
 
 import pytest
 
@@ -197,6 +197,21 @@ def test_method(self):
     assert method.__self__ == instance
 
 
+@pytest.mark.asyncio
+@pytest.mark.parametrize("exc_cls", (RuntimeError, ValueError, Exception))
+async def test_sync_to_async_broken_executor(exc_cls):
+    """
+    Tests sync_to_async catch error in executor and avoid deadlock
+    """
+    with mock.patch.object(ThreadPoolExecutor, "submit") as mock_run:
+        mock_run.side_effect = exc_cls("Test Error")
+        async_function = sync_to_async(lambda: None, thread_sensitive=True)
+        with pytest.raises(exc_cls, match="Test Error"):
+            await async_function()
+        with pytest.raises(exc_cls, match="Test Error"):
+            await async_function()
+
+
 @pytest.mark.asyncio
 async def test_async_to_sync_to_async():
     """