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[3.13] gh-117657: Fix data races reported by TSAN on interp->threads.main (GH-118865) #118904

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merged 1 commit into from
May 10, 2024
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[3.13] gh-117657: Fix data races reported by TSAN on interp->threads.main (GH-118865) #118904

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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core and Builtins/2024-05-09-19-47-12.gh-issue-117657.Vn0Yey.rst
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Original file line number Diff line number Diff line change
@@ -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.
31 changes: 20 additions & 11 deletions Python/pystate.c
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Expand Up @@ -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)
Expand All @@ -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(),
Expand All @@ -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;
Expand All @@ -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);
}
}

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2 changes: 0 additions & 2 deletions Tools/tsan/suppressions_free_threading.txt
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Expand Up @@ -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
Expand Down
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