https://github.com/python/cpython/commit/22d5185308f85efa22ec1e8251c409fe1cbd9e6b
commit: 22d5185308f85efa22ec1e8251c409fe1cbd9e6b
branch: main
author: mpage <[email protected]>
committer: colesbury <[email protected]>
date: 2024-05-10T09:59:14-04:00
summary:
gh-117657: Fix data races reported by TSAN on `interp->threads.main` (#118865)
Use relaxed loads/stores when reading/writing to this field.
files:
A Misc/NEWS.d/next/Core and
Builtins/2024-05-09-19-47-12.gh-issue-117657.Vn0Yey.rst
M Python/pystate.c
M Tools/tsan/suppressions_free_threading.txt
diff --git a/Misc/NEWS.d/next/Core and
Builtins/2024-05-09-19-47-12.gh-issue-117657.Vn0Yey.rst b/Misc/NEWS.d/next/Core
and Builtins/2024-05-09-19-47-12.gh-issue-117657.Vn0Yey.rst
new file mode 100644
index 00000000000000..db4c5813ca610c
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and
Builtins/2024-05-09-19-47-12.gh-issue-117657.Vn0Yey.rst
@@ -0,0 +1 @@
+Fix data races on the field that stores a pointer to the interpreter's main
thread that occur in free-threaded builds.
diff --git a/Python/pystate.c b/Python/pystate.c
index b1e085bb806915..de6a768a50f997 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -1038,6 +1038,17 @@ _PyInterpreterState_DeleteExceptMain(_PyRuntimeState
*runtime)
}
#endif
+static inline void
+set_main_thread(PyInterpreterState *interp, PyThreadState *tstate)
+{
+ _Py_atomic_store_ptr_relaxed(&interp->threads.main, tstate);
+}
+
+static inline PyThreadState *
+get_main_thread(PyInterpreterState *interp)
+{
+ return _Py_atomic_load_ptr_relaxed(&interp->threads.main);
+}
int
_PyInterpreterState_SetRunningMain(PyInterpreterState *interp)
@@ -1052,21 +1063,22 @@ _PyInterpreterState_SetRunningMain(PyInterpreterState
*interp)
"current tstate has wrong interpreter");
return -1;
}
- interp->threads.main = tstate;
+ set_main_thread(interp, tstate);
+
return 0;
}
void
_PyInterpreterState_SetNotRunningMain(PyInterpreterState *interp)
{
- assert(interp->threads.main == current_fast_get());
- interp->threads.main = NULL;
+ assert(get_main_thread(interp) == current_fast_get());
+ set_main_thread(interp, NULL);
}
int
_PyInterpreterState_IsRunningMain(PyInterpreterState *interp)
{
- if (interp->threads.main != NULL) {
+ if (get_main_thread(interp) != NULL) {
return 1;
}
// Embedders might not know to call _PyInterpreterState_SetRunningMain(),
@@ -1082,18 +1094,15 @@ int
_PyThreadState_IsRunningMain(PyThreadState *tstate)
{
PyInterpreterState *interp = tstate->interp;
- if (interp->threads.main != NULL) {
- return tstate == interp->threads.main;
- }
// See the note in _PyInterpreterState_IsRunningMain() about
// possible false negatives here for embedders.
- return 0;
+ return get_main_thread(interp) == tstate;
}
int
_PyInterpreterState_FailIfRunningMain(PyInterpreterState *interp)
{
- if (interp->threads.main != NULL) {
+ if (get_main_thread(interp) != NULL) {
PyErr_SetString(PyExc_InterpreterError,
"interpreter already running");
return -1;
@@ -1105,8 +1114,8 @@ void
_PyInterpreterState_ReinitRunningMain(PyThreadState *tstate)
{
PyInterpreterState *interp = tstate->interp;
- if (interp->threads.main != tstate) {
- interp->threads.main = NULL;
+ if (get_main_thread(interp) != tstate) {
+ set_main_thread(interp, NULL);
}
}
diff --git a/Tools/tsan/suppressions_free_threading.txt
b/Tools/tsan/suppressions_free_threading.txt
index 7f91a9113c4e1a..d5f4cd7acd36b7 100644
--- a/Tools/tsan/suppressions_free_threading.txt
+++ b/Tools/tsan/suppressions_free_threading.txt
@@ -33,8 +33,6 @@ race_top:_mi_heap_delayed_free_partial
race_top:_PyEval_EvalFrameDefault
race_top:_PyImport_AcquireLock
race_top:_PyImport_ReleaseLock
-race_top:_PyInterpreterState_SetNotRunningMain
-race_top:_PyInterpreterState_IsRunningMain
# https://gist.github.com/mpage/0a24eb2dd458441ededb498e9b0e5de8
race_top:_PyParkingLot_Park
race_top:_PyType_HasFeature
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