1 files changed, 34 insertions, 4 deletions
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index 2003546ce84..cc1a5580015 100644
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -1880,8 +1880,8 @@ chain_traverse(PyObject *op, visitproc visit, void *arg)
     return 0;
 }
 
-static PyObject *
-chain_next(PyObject *op)
+static inline PyObject *
+chain_next_lock_held(PyObject *op)
 {
     chainobject *lz = chainobject_CAST(op);
     PyObject *item;
@@ -1919,6 +1919,16 @@ chain_next(PyObject *op)
     return NULL;
 }
 
+static PyObject *
+chain_next(PyObject *op)
+{
+    PyObject *result;
+    Py_BEGIN_CRITICAL_SECTION(op);
+    result = chain_next_lock_held(op);
+    Py_END_CRITICAL_SECTION()
+    return result;
+}
+
 PyDoc_STRVAR(chain_doc,
 "chain(*iterables)\n\
 --\n\
@@ -2086,7 +2096,7 @@ product_traverse(PyObject *op, visitproc visit, void *arg)
 }
 
 static PyObject *
-product_next(PyObject *op)
+product_next_lock_held(PyObject *op)
 {
     productobject *lz = productobject_CAST(op);
     PyObject *pool;
@@ -2172,6 +2182,16 @@ empty:
     return NULL;
 }
 
+static PyObject *
+product_next(PyObject *op)
+{
+    PyObject *result;
+    Py_BEGIN_CRITICAL_SECTION(op);
+    result = product_next_lock_held(op);
+    Py_END_CRITICAL_SECTION()
+    return result;
+}
+
 static PyMethodDef product_methods[] = {
     {"__sizeof__", product_sizeof, METH_NOARGS, sizeof_doc},
     {NULL,              NULL}   /* sentinel */
@@ -2319,7 +2339,7 @@ combinations_traverse(PyObject *op, visitproc visit, void *arg)
 }
 
 static PyObject *
-combinations_next(PyObject *op)
+combinations_next_lock_held(PyObject *op)
 {
     combinationsobject *co = combinationsobject_CAST(op);
     PyObject *elem;
@@ -2404,6 +2424,16 @@ empty:
     return NULL;
 }
 
+static PyObject *
+combinations_next(PyObject *op)
+{
+    PyObject *result;
+    Py_BEGIN_CRITICAL_SECTION(op);
+    result = combinations_next_lock_held(op);
+    Py_END_CRITICAL_SECTION()
+    return result;
+}
+
 static PyMethodDef combinations_methods[] = {
     {"__sizeof__", combinations_sizeof, METH_NOARGS, sizeof_doc},
     {NULL,              NULL}   /* sentinel */