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gh-137400: Stop the world when swapping profile functions #137472

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gh-137400: Stop the world when swapping profile functions
godlygeek Aug 6, 2025
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godlygeek Aug 6, 2025
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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2025-08-06-11-56-15.gh-issue-137472.Pr_BLB.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Fix a crash that can occur in free-threading builds when
``sys._setprofileallthreads`` or ``sys._settraceallthreads`` changes the
profile function underneath a running thread.
8 changes: 7 additions & 1 deletion Python/legacy_tracing.c
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Expand Up @@ -484,13 +484,19 @@ setup_profile(PyThreadState *tstate, Py_tracefunc func, PyObject *arg, PyObject
}
}

_PyEval_StopTheWorld(tstate->interp);

int delta = (func != NULL) - (tstate->c_profilefunc != NULL);
tstate->c_profilefunc = func;
*old_profileobj = tstate->c_profileobj;
tstate->c_profileobj = Py_XNewRef(arg);
tstate->interp->sys_profiling_threads += delta;
assert(tstate->interp->sys_profiling_threads >= 0);
return tstate->interp->sys_profiling_threads;
Py_ssize_t ret = tstate->interp->sys_profiling_threads;

_PyEval_StartTheWorld(tstate->interp);

return ret;
}

int
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