[Python-checkins] bpo-46070: _PyGC_Fini() untracks objects (GH-30577) (GH-30580)
vstinner
webhook-mailer at python.org
Thu Jan 13 14:12:59 EST 2022
https://github.com/python/cpython/commit/52937c26adc35350ca0402070160cf6dc838f359
commit: 52937c26adc35350ca0402070160cf6dc838f359
branch: 3.9
author: Victor Stinner <vstinner at python.org>
committer: vstinner <vstinner at python.org>
date: 2022-01-13T20:12:50+01:00
summary:
bpo-46070: _PyGC_Fini() untracks objects (GH-30577) (GH-30580)
Py_EndInterpreter() now explicitly untracks all objects currently
tracked by the GC. Previously, if an object was used later by another
interpreter, calling PyObject_GC_UnTrack() on the object crashed if
the previous or the next object of the PyGC_Head structure became a
dangling pointer.
(cherry picked from commit 1a4d1c1c9b08e75e88aeac90901920938f649832)
files:
A Misc/NEWS.d/next/Core and Builtins/2022-01-13-17-58-56.bpo-46070.q8IGth.rst
M Modules/gcmodule.c
diff --git a/Misc/NEWS.d/next/Core and Builtins/2022-01-13-17-58-56.bpo-46070.q8IGth.rst b/Misc/NEWS.d/next/Core and Builtins/2022-01-13-17-58-56.bpo-46070.q8IGth.rst
new file mode 100644
index 0000000000000..4ed088f9898eb
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2022-01-13-17-58-56.bpo-46070.q8IGth.rst
@@ -0,0 +1,5 @@
+:c:func:`Py_EndInterpreter` now explicitly untracks all objects currently
+tracked by the GC. Previously, if an object was used later by another
+interpreter, calling :c:func:`PyObject_GC_UnTrack` on the object crashed if the
+previous or the next object of the :c:type:`PyGC_Head` structure became a
+dangling pointer. Patch by Victor Stinner.
diff --git a/Modules/gcmodule.c b/Modules/gcmodule.c
index 2c6ef9252eae8..3cf1a00b003b3 100644
--- a/Modules/gcmodule.c
+++ b/Modules/gcmodule.c
@@ -2149,12 +2149,36 @@ _PyGC_DumpShutdownStats(PyThreadState *tstate)
}
}
+
+static void
+gc_fini_untrack(PyGC_Head *list)
+{
+ PyGC_Head *gc;
+ for (gc = GC_NEXT(list); gc != list; gc = GC_NEXT(list)) {
+ PyObject *op = FROM_GC(gc);
+ _PyObject_GC_UNTRACK(op);
+ }
+}
+
+
void
_PyGC_Fini(PyThreadState *tstate)
{
GCState *gcstate = &tstate->interp->gc;
Py_CLEAR(gcstate->garbage);
Py_CLEAR(gcstate->callbacks);
+
+ if (!_Py_IsMainInterpreter(tstate)) {
+ // bpo-46070: Explicitly untrack all objects currently tracked by the
+ // GC. Otherwise, if an object is used later by another interpreter,
+ // calling PyObject_GC_UnTrack() on the object crashs if the previous
+ // or the next object of the PyGC_Head structure became a dangling
+ // pointer.
+ for (int i = 0; i < NUM_GENERATIONS; i++) {
+ PyGC_Head *gen = GEN_HEAD(gcstate, i);
+ gc_fini_untrack(gen);
+ }
+ }
}
/* for debugging */
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