pythongh-117657: Fix TSAN reported race in _PyEval_IsGILEnabled. (python#119921)

colesbury · barneygale · commit e2633ae4fbe4 · 2024-06-05T19:00:59.000+01:00
The GIL may be disabled concurrently with this call so we need to use a
relaxed atomic load.
diff --git a/Include/internal/pycore_ceval.h b/Include/internal/pycore_ceval.h
@@ -145,7 +145,8 @@ extern void _PyEval_ReleaseLock(PyInterpreterState *, PyThreadState *,
 static inline int
 _PyEval_IsGILEnabled(PyThreadState *tstate)
 {
-    return tstate->interp->ceval.gil->enabled != 0;
+    struct _gil_runtime_state *gil = tstate->interp->ceval.gil;
+    return _Py_atomic_load_int_relaxed(&gil->enabled) != 0;
 }
 
 // Enable or disable the GIL used by the interpreter that owns tstate, which
diff --git a/Tools/tsan/suppressions_free_threading.txt b/Tools/tsan/suppressions_free_threading.txt
@@ -65,7 +65,6 @@ race_top:list_get_item_ref
 race_top:make_pending_calls
 race_top:set_add_entry
 race_top:should_intern_string
-race_top:_PyEval_IsGILEnabled
 race_top:llist_insert_tail
 race_top:_Py_slot_tp_getattr_hook
 race_top:add_threadstate

Original file line number	Diff line number	Diff line change
`@@ -145,7 +145,8 @@ extern void _PyEval_ReleaseLock(PyInterpreterState , PyThreadState ,`
`145`	`145`	`static inline int`
`146`	`146`	`_PyEval_IsGILEnabled(PyThreadState *tstate)`
`147`	`147`	`{`
`148`		`- return tstate->interp->ceval.gil->enabled != 0;`
	`148`	`+ struct _gil_runtime_state *gil = tstate->interp->ceval.gil;`
	`149`	`+ return _Py_atomic_load_int_relaxed(&gil->enabled) != 0;`
`149`	`150`	`}`
`150`	`151`
`151`	`152`	`// Enable or disable the GIL used by the interpreter that owns tstate, which`