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gh-127266: avoid data races when updating type slots (gh-131174)

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In the free-threaded build, avoid data races caused by updating type slots
or type flags after the type was initially created.  For those (typically
rare) cases, use the stop-the-world mechanism.  Remove the use of atomics
when reading or writing type flags.  The use of atomics is not sufficient to
avoid races (since flags are sometimes read without a lock and without
atomics) and are no longer required.
This commit is contained in:
Neil Schemenauer 2025-04-28 13:28:44 -07:00 • committed by GitHub
parent 22f0730d40
commit e414a2d81c
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10 changed files with 233 additions and 112 deletions
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14
Python/ceval.c
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@ -138,6 +138,19 @@
#endif
static void
check_invalid_reentrancy(void)
{
#if defined(Py_DEBUG) && defined(Py_GIL_DISABLED)
// In the free-threaded build, the interpreter must not be re-entered if
// the world-is-stopped. If so, that's a bug somewhere (quite likely in
// the painfully complex typeobject code).
PyInterpreterState *interp = _PyInterpreterState_GET();
assert(!interp->stoptheworld.world_stopped);
#endif
}
#ifdef Py_DEBUG
static void
dump_item(_PyStackRef item)
@ -995,6 +1008,7 @@ PyObject* _Py_HOT_FUNCTION DONT_SLP_VECTORIZE
_PyEval_EvalFrameDefault(PyThreadState *tstate, _PyInterpreterFrame *frame, int throwflag)
{
_Py_EnsureTstateNotNULL(tstate);
check_invalid_reentrancy();
CALL_STAT_INC(pyeval_calls);
#if USE_COMPUTED_GOTOS && !Py_TAIL_CALL_INTERP