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gh-130091: Reorder _PyThreadState_Attach to avoid data race (gh-130092)

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This moves `tstate_activate()` down to avoid a data race in the free
threading build on the `_PyRuntime`'s thread-local `autoTSSkey`. This
key is deleted during runtime finalization, which may happen
concurrently with a call to `_PyThreadState_Attach`.

The earlier `tstate_try/wait_attach` ensures that the thread is blocked
before it attempts to access the deleted `autoTSSkey`.

This fixes a TSAN reported data race in
`test_threading.test_import_from_another_thread`.
This commit is contained in:
Sam Gross 2025-02-27 13:57:19 -05:00 • committed by GitHub
parent e06bebb87e
commit 7aeaa5af2c
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1 changed files with 1 additions and 2 deletions
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Python/pystate.c
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@ -2099,11 +2099,10 @@ _PyThreadState_Attach(PyThreadState *tstate)
// XXX assert(tstate_is_alive(tstate)); // XXX assert(tstate_is_alive(tstate));
current_fast_set(&_PyRuntime, tstate); current_fast_set(&_PyRuntime, tstate);
tstate_activate(tstate);
if (!tstate_try_attach(tstate)) { if (!tstate_try_attach(tstate)) {
tstate_wait_attach(tstate); tstate_wait_attach(tstate);
} }
tstate_activate(tstate);
#ifdef Py_GIL_DISABLED #ifdef Py_GIL_DISABLED
if (_PyEval_IsGILEnabled(tstate) && !tstate->_status.holds_gil) { if (_PyEval_IsGILEnabled(tstate) && !tstate->_status.holds_gil) {