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gh-117657: Fix data races reported by TSAN on interp->threads.main #118865

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Merged
merged 4 commits into from
May 10, 2024
Merged

gh-117657: Fix data races reported by TSAN on interp->threads.main #118865

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50cf12b
Fix data races reported by TSAN on `interp->threads.main`
mpage May 9, 2024
f412a0c
📜🤖 Added by blurb_it.
blurb-it[bot] May 9, 2024
7c9e286
Merge branch 'main' into gh-117657-tsan-is-running-main
mpage May 9, 2024
17d8622
Remove corresponding suppressions
mpage May 9, 2024
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Fix data races reported by TSAN on interp->threads.main 
Use relaxed loads/stores when reading/writing to this field.

This fixes races like https://gist.github.com/mpage/e07497ad8dd444a789ff306cb7996acc
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@mpage
mpage committed May 9, 2024
commit 50cf12b2e9d73d20723ef7fbc0d5aad27edbbfb0
31 changes: 20 additions & 11 deletions Python/pystate.c
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Original file line number Diff line number Diff line change
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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