Prevent recursive script calls from deadlocking (#67861)

* Prevent recursive script calls from deadlocking

* Address review comments, improve tests

* Tweak comment

homeassistant/helpers/script.py

@@ -4,6 +4,7 @@ from __future__ import annotations
 import asyncio
 from collections.abc import Callable, Sequence
 from contextlib import asynccontextmanager, suppress
+from contextvars import ContextVar
 from datetime import datetime, timedelta
 from functools import partial
 import itertools
@@ -126,6 +127,8 @@ SCRIPT_BREAKPOINT_HIT = "script_breakpoint_hit"
 SCRIPT_DEBUG_CONTINUE_STOP = "script_debug_continue_stop_{}_{}"
 SCRIPT_DEBUG_CONTINUE_ALL = "script_debug_continue_all"
 
+script_stack_cv: ContextVar[list[int] | None] = ContextVar("script_stack", default=None)
+
 
 def action_trace_append(variables, path):
     """Append a TraceElement to trace[path]."""
@@ -340,6 +343,12 @@ class _ScriptRun:
 
     async def async_run(self) -> None:
         """Run script."""
+        # Push the script to the script execution stack
+        if (script_stack := script_stack_cv.get()) is None:
+            script_stack = []
+            script_stack_cv.set(script_stack)
+        script_stack.append(id(self._script))
+
         try:
             self._log("Running %s", self._script.running_description)
             for self._step, self._action in enumerate(self._script.sequence):
@@ -355,6 +364,8 @@ class _ScriptRun:
             script_execution_set("error")
             raise
         finally:
+            # Pop the script from the script execution stack
+            script_stack.pop()
             self._finish()
 
     async def _async_step(self, log_exceptions):
@@ -1218,6 +1229,18 @@ class Script:
         else:
             variables = cast(dict, run_variables)
 
+        # Prevent non-allowed recursive calls which will cause deadlocks when we try to
+        # stop (restart) or wait for (queued) our own script run.
+        script_stack = script_stack_cv.get()
+        if (
+            self.script_mode in (SCRIPT_MODE_RESTART, SCRIPT_MODE_QUEUED)
+            and (script_stack := script_stack_cv.get()) is not None
+            and id(self) in script_stack
+        ):
+            script_execution_set("disallowed_recursion_detected")
+            _LOGGER.warning("Disallowed recursion detected")
+            return
+
         if self.script_mode != SCRIPT_MODE_QUEUED:
             cls = _ScriptRun
         else: