diff --git a/Modules/_io/clinic/stringio.c.h b/Modules/_io/clinic/stringio.c.h
index 571ec511714..8e5c687dc6a 100644
--- a/Modules/_io/clinic/stringio.c.h
+++ b/Modules/_io/clinic/stringio.c.h
@@ -7,6 +7,7 @@ preserve
 #  include "pycore_runtime.h"     // _Py_ID()
 #endif
 #include "pycore_abstract.h"      // _Py_convert_optional_to_ssize_t()
+#include "pycore_critical_section.h"// Py_BEGIN_CRITICAL_SECTION()
 #include "pycore_modsupport.h"    // _PyArg_CheckPositional()
 
 PyDoc_STRVAR(_io_StringIO_getvalue__doc__,
@@ -24,7 +25,13 @@ _io_StringIO_getvalue_impl(stringio *self);
 static PyObject *
 _io_StringIO_getvalue(stringio *self, PyObject *Py_UNUSED(ignored))
 {
-    return _io_StringIO_getvalue_impl(self);
+    PyObject *return_value = NULL;
+
+    Py_BEGIN_CRITICAL_SECTION(self);
+    return_value = _io_StringIO_getvalue_impl(self);
+    Py_END_CRITICAL_SECTION();
+
+    return return_value;
 }
 
 PyDoc_STRVAR(_io_StringIO_tell__doc__,
@@ -42,7 +49,13 @@ _io_StringIO_tell_impl(stringio *self);
 static PyObject *
 _io_StringIO_tell(stringio *self, PyObject *Py_UNUSED(ignored))
 {
-    return _io_StringIO_tell_impl(self);
+    PyObject *return_value = NULL;
+
+    Py_BEGIN_CRITICAL_SECTION(self);
+    return_value = _io_StringIO_tell_impl(self);
+    Py_END_CRITICAL_SECTION();
+
+    return return_value;
 }
 
 PyDoc_STRVAR(_io_StringIO_read__doc__,
@@ -76,7 +89,9 @@ _io_StringIO_read(stringio *self, PyObject *const *args, Py_ssize_t nargs)
         goto exit;
     }
 skip_optional:
+    Py_BEGIN_CRITICAL_SECTION(self);
     return_value = _io_StringIO_read_impl(self, size);
+    Py_END_CRITICAL_SECTION();
 
 exit:
     return return_value;
@@ -112,7 +127,9 @@ _io_StringIO_readline(stringio *self, PyObject *const *args, Py_ssize_t nargs)
         goto exit;
     }
 skip_optional:
+    Py_BEGIN_CRITICAL_SECTION(self);
     return_value = _io_StringIO_readline_impl(self, size);
+    Py_END_CRITICAL_SECTION();
 
 exit:
     return return_value;
@@ -150,7 +167,9 @@ _io_StringIO_truncate(stringio *self, PyObject *const *args, Py_ssize_t nargs)
         goto exit;
     }
 skip_optional:
+    Py_BEGIN_CRITICAL_SECTION(self);
     return_value = _io_StringIO_truncate_impl(self, size);
+    Py_END_CRITICAL_SECTION();
 
 exit:
     return return_value;
@@ -204,7 +223,9 @@ _io_StringIO_seek(stringio *self, PyObject *const *args, Py_ssize_t nargs)
         goto exit;
     }
 skip_optional:
+    Py_BEGIN_CRITICAL_SECTION(self);
     return_value = _io_StringIO_seek_impl(self, pos, whence);
+    Py_END_CRITICAL_SECTION();
 
 exit:
     return return_value;
@@ -222,6 +243,21 @@ PyDoc_STRVAR(_io_StringIO_write__doc__,
 #define _IO_STRINGIO_WRITE_METHODDEF    \
     {"write", (PyCFunction)_io_StringIO_write, METH_O, _io_StringIO_write__doc__},
 
+static PyObject *
+_io_StringIO_write_impl(stringio *self, PyObject *obj);
+
+static PyObject *
+_io_StringIO_write(stringio *self, PyObject *obj)
+{
+    PyObject *return_value = NULL;
+
+    Py_BEGIN_CRITICAL_SECTION(self);
+    return_value = _io_StringIO_write_impl(self, obj);
+    Py_END_CRITICAL_SECTION();
+
+    return return_value;
+}
+
 PyDoc_STRVAR(_io_StringIO_close__doc__,
 "close($self, /)\n"
 "--\n"
@@ -242,7 +278,13 @@ _io_StringIO_close_impl(stringio *self);
 static PyObject *
 _io_StringIO_close(stringio *self, PyObject *Py_UNUSED(ignored))
 {
-    return _io_StringIO_close_impl(self);
+    PyObject *return_value = NULL;
+
+    Py_BEGIN_CRITICAL_SECTION(self);
+    return_value = _io_StringIO_close_impl(self);
+    Py_END_CRITICAL_SECTION();
+
+    return return_value;
 }
 
 PyDoc_STRVAR(_io_StringIO___init____doc__,
@@ -330,7 +372,13 @@ _io_StringIO_readable_impl(stringio *self);
 static PyObject *
 _io_StringIO_readable(stringio *self, PyObject *Py_UNUSED(ignored))
 {
-    return _io_StringIO_readable_impl(self);
+    PyObject *return_value = NULL;
+
+    Py_BEGIN_CRITICAL_SECTION(self);
+    return_value = _io_StringIO_readable_impl(self);
+    Py_END_CRITICAL_SECTION();
+
+    return return_value;
 }
 
 PyDoc_STRVAR(_io_StringIO_writable__doc__,
@@ -348,7 +396,13 @@ _io_StringIO_writable_impl(stringio *self);
 static PyObject *
 _io_StringIO_writable(stringio *self, PyObject *Py_UNUSED(ignored))
 {
-    return _io_StringIO_writable_impl(self);
+    PyObject *return_value = NULL;
+
+    Py_BEGIN_CRITICAL_SECTION(self);
+    return_value = _io_StringIO_writable_impl(self);
+    Py_END_CRITICAL_SECTION();
+
+    return return_value;
 }
 
 PyDoc_STRVAR(_io_StringIO_seekable__doc__,
@@ -366,6 +420,58 @@ _io_StringIO_seekable_impl(stringio *self);
 static PyObject *
 _io_StringIO_seekable(stringio *self, PyObject *Py_UNUSED(ignored))
 {
-    return _io_StringIO_seekable_impl(self);
+    PyObject *return_value = NULL;
+
+    Py_BEGIN_CRITICAL_SECTION(self);
+    return_value = _io_StringIO_seekable_impl(self);
+    Py_END_CRITICAL_SECTION();
+
+    return return_value;
 }
-/*[clinic end generated code: output=f56aa7f8a271acf6 input=a9049054013a1b77]*/
+
+PyDoc_STRVAR(_io_StringIO___getstate____doc__,
+"__getstate__($self, /)\n"
+"--\n"
+"\n");
+
+#define _IO_STRINGIO___GETSTATE___METHODDEF    \
+    {"__getstate__", (PyCFunction)_io_StringIO___getstate__, METH_NOARGS, _io_StringIO___getstate____doc__},
+
+static PyObject *
+_io_StringIO___getstate___impl(stringio *self);
+
+static PyObject *
+_io_StringIO___getstate__(stringio *self, PyObject *Py_UNUSED(ignored))
+{
+    PyObject *return_value = NULL;
+
+    Py_BEGIN_CRITICAL_SECTION(self);
+    return_value = _io_StringIO___getstate___impl(self);
+    Py_END_CRITICAL_SECTION();
+
+    return return_value;
+}
+
+PyDoc_STRVAR(_io_StringIO___setstate____doc__,
+"__setstate__($self, state, /)\n"
+"--\n"
+"\n");
+
+#define _IO_STRINGIO___SETSTATE___METHODDEF    \
+    {"__setstate__", (PyCFunction)_io_StringIO___setstate__, METH_O, _io_StringIO___setstate____doc__},
+
+static PyObject *
+_io_StringIO___setstate___impl(stringio *self, PyObject *state);
+
+static PyObject *
+_io_StringIO___setstate__(stringio *self, PyObject *state)
+{
+    PyObject *return_value = NULL;
+
+    Py_BEGIN_CRITICAL_SECTION(self);
+    return_value = _io_StringIO___setstate___impl(self, state);
+    Py_END_CRITICAL_SECTION();
+
+    return return_value;
+}
+/*[clinic end generated code: output=5c8d67f4408a1e6e input=a9049054013a1b77]*/
diff --git a/Modules/_io/stringio.c b/Modules/_io/stringio.c
index 1856b07108b..0aa5e34cd7c 100644
--- a/Modules/_io/stringio.c
+++ b/Modules/_io/stringio.c
@@ -45,6 +45,10 @@ typedef struct {
     _PyIO_State *module_state;
 } stringio;
 
+#define clinic_state() (find_io_state_by_def(Py_TYPE(self)))
+#include "clinic/stringio.c.h"
+#undef clinic_state
+
 static int _io_StringIO___init__(PyObject *self, PyObject *args, PyObject *kwargs);
 
 #define CHECK_INITIALIZED(self) \
@@ -263,6 +267,7 @@ write_str(stringio *self, PyObject *obj)
 }
 
 /*[clinic input]
+@critical_section
 _io.StringIO.getvalue
 
 Retrieve the entire contents of the object.
@@ -270,7 +275,7 @@ Retrieve the entire contents of the object.
 
 static PyObject *
 _io_StringIO_getvalue_impl(stringio *self)
-/*[clinic end generated code: output=27b6a7bfeaebce01 input=d23cb81d6791cf88]*/
+/*[clinic end generated code: output=27b6a7bfeaebce01 input=fb5dee06b8d467f3]*/
 {
     CHECK_INITIALIZED(self);
     CHECK_CLOSED(self);
@@ -281,6 +286,7 @@ _io_StringIO_getvalue_impl(stringio *self)
 }
 
 /*[clinic input]
+@critical_section
 _io.StringIO.tell
 
 Tell the current file position.
@@ -288,7 +294,7 @@ Tell the current file position.
 
 static PyObject *
 _io_StringIO_tell_impl(stringio *self)
-/*[clinic end generated code: output=2e87ac67b116c77b input=ec866ebaff02f405]*/
+/*[clinic end generated code: output=2e87ac67b116c77b input=98a08f3e2dae3550]*/
 {
     CHECK_INITIALIZED(self);
     CHECK_CLOSED(self);
@@ -296,6 +302,7 @@ _io_StringIO_tell_impl(stringio *self)
 }
 
 /*[clinic input]
+@critical_section
 _io.StringIO.read
     size: Py_ssize_t(accept={int, NoneType}) = -1
     /
@@ -308,7 +315,7 @@ is reached. Return an empty string at EOF.
 
 static PyObject *
 _io_StringIO_read_impl(stringio *self, Py_ssize_t size)
-/*[clinic end generated code: output=ae8cf6002f71626c input=0921093383dfb92d]*/
+/*[clinic end generated code: output=ae8cf6002f71626c input=9fbef45d8aece8e7]*/
 {
     Py_ssize_t n;
     Py_UCS4 *output;
@@ -368,6 +375,7 @@ _stringio_readline(stringio *self, Py_ssize_t limit)
 }
 
 /*[clinic input]
+@critical_section
 _io.StringIO.readline
     size: Py_ssize_t(accept={int, NoneType}) = -1
     /
@@ -379,7 +387,7 @@ Returns an empty string if EOF is hit immediately.
 
 static PyObject *
 _io_StringIO_readline_impl(stringio *self, Py_ssize_t size)
-/*[clinic end generated code: output=cabd6452f1b7e85d input=a5bd70bf682aa276]*/
+/*[clinic end generated code: output=cabd6452f1b7e85d input=4d14b8495dea1d98]*/
 {
     CHECK_INITIALIZED(self);
     CHECK_CLOSED(self);
@@ -427,6 +435,7 @@ stringio_iternext(stringio *self)
 }
 
 /*[clinic input]
+@critical_section
 _io.StringIO.truncate
     pos as size: Py_ssize_t(accept={int, NoneType}, c_default="self->pos") = None
     /
@@ -440,7 +449,7 @@ Returns the new absolute position.
 
 static PyObject *
 _io_StringIO_truncate_impl(stringio *self, Py_ssize_t size)
-/*[clinic end generated code: output=eb3aef8e06701365 input=5505cff90ca48b96]*/
+/*[clinic end generated code: output=eb3aef8e06701365 input=461b872dce238452]*/
 {
     CHECK_INITIALIZED(self);
     CHECK_CLOSED(self);
@@ -462,6 +471,7 @@ _io_StringIO_truncate_impl(stringio *self, Py_ssize_t size)
 }
 
 /*[clinic input]
+@critical_section
 _io.StringIO.seek
     pos: Py_ssize_t
     whence: int = 0
@@ -478,7 +488,7 @@ Returns the new absolute position.
 
 static PyObject *
 _io_StringIO_seek_impl(stringio *self, Py_ssize_t pos, int whence)
-/*[clinic end generated code: output=e9e0ac9a8ae71c25 input=e3855b24e7cae06a]*/
+/*[clinic end generated code: output=e9e0ac9a8ae71c25 input=c75ced09343a00d7]*/
 {
     CHECK_INITIALIZED(self);
     CHECK_CLOSED(self);
@@ -515,6 +525,7 @@ _io_StringIO_seek_impl(stringio *self, Py_ssize_t pos, int whence)
 }
 
 /*[clinic input]
+@critical_section
 _io.StringIO.write
     s as obj: object
     /
@@ -526,8 +537,8 @@ the length of the string.
 [clinic start generated code]*/
 
 static PyObject *
-_io_StringIO_write(stringio *self, PyObject *obj)
-/*[clinic end generated code: output=0deaba91a15b94da input=cf96f3b16586e669]*/
+_io_StringIO_write_impl(stringio *self, PyObject *obj)
+/*[clinic end generated code: output=d53b1d841d7db288 input=1561272c0da4651f]*/
 {
     Py_ssize_t size;
 
@@ -547,6 +558,7 @@ _io_StringIO_write(stringio *self, PyObject *obj)
 }
 
 /*[clinic input]
+@critical_section
 _io.StringIO.close
 
 Close the IO object.
@@ -559,7 +571,7 @@ This method has no effect if the file is already closed.
 
 static PyObject *
 _io_StringIO_close_impl(stringio *self)
-/*[clinic end generated code: output=04399355cbe518f1 input=cbc10b45f35d6d46]*/
+/*[clinic end generated code: output=04399355cbe518f1 input=305d19aa29cc40b9]*/
 {
     self->closed = 1;
     /* Free up some memory */
@@ -756,6 +768,7 @@ _io_StringIO___init___impl(stringio *self, PyObject *value,
 /* Properties and pseudo-properties */
 
 /*[clinic input]
+@critical_section
 _io.StringIO.readable
 
 Returns True if the IO object can be read.
@@ -763,7 +776,7 @@ Returns True if the IO object can be read.
 
 static PyObject *
 _io_StringIO_readable_impl(stringio *self)
-/*[clinic end generated code: output=b19d44dd8b1ceb99 input=39ce068b224c21ad]*/
+/*[clinic end generated code: output=b19d44dd8b1ceb99 input=6cd2ffd65a8e8763]*/
 {
     CHECK_INITIALIZED(self);
     CHECK_CLOSED(self);
@@ -771,6 +784,7 @@ _io_StringIO_readable_impl(stringio *self)
 }
 
 /*[clinic input]
+@critical_section
 _io.StringIO.writable
 
 Returns True if the IO object can be written.
@@ -778,7 +792,7 @@ Returns True if the IO object can be written.
 
 static PyObject *
 _io_StringIO_writable_impl(stringio *self)
-/*[clinic end generated code: output=13e4dd77187074ca input=7a691353aac38835]*/
+/*[clinic end generated code: output=13e4dd77187074ca input=1b3c63dbaa761c69]*/
 {
     CHECK_INITIALIZED(self);
     CHECK_CLOSED(self);
@@ -786,6 +800,7 @@ _io_StringIO_writable_impl(stringio *self)
 }
 
 /*[clinic input]
+@critical_section
 _io.StringIO.seekable
 
 Returns True if the IO object can be seeked.
@@ -793,7 +808,7 @@ Returns True if the IO object can be seeked.
 
 static PyObject *
 _io_StringIO_seekable_impl(stringio *self)
-/*[clinic end generated code: output=4d20b4641c756879 input=4c606d05b32952e6]*/
+/*[clinic end generated code: output=4d20b4641c756879 input=a820fad2cf085fc3]*/
 {
     CHECK_INITIALIZED(self);
     CHECK_CLOSED(self);
@@ -812,8 +827,15 @@ _io_StringIO_seekable_impl(stringio *self)
    supported.
 */
 
+/*[clinic input]
+@critical_section
+_io.StringIO.__getstate__
+
+[clinic start generated code]*/
+
 static PyObject *
-stringio_getstate(stringio *self, PyObject *Py_UNUSED(ignored))
+_io_StringIO___getstate___impl(stringio *self)
+/*[clinic end generated code: output=780be4a996410199 input=76f27255ef83bb92]*/
 {
     PyObject *initvalue = _io_StringIO_getvalue_impl(self);
     PyObject *dict;
@@ -839,8 +861,17 @@ stringio_getstate(stringio *self, PyObject *Py_UNUSED(ignored))
     return state;
 }
 
+/*[clinic input]
+@critical_section
+_io.StringIO.__setstate__
+
+    state: object
+    /
+[clinic start generated code]*/
+
 static PyObject *
-stringio_setstate(stringio *self, PyObject *state)
+_io_StringIO___setstate___impl(stringio *self, PyObject *state)
+/*[clinic end generated code: output=cb3962bc6d5c5609 input=8a27784b11b82e47]*/
 {
     PyObject *initarg;
     PyObject *position_obj;
@@ -941,14 +972,24 @@ stringio_setstate(stringio *self, PyObject *state)
 
 
 static PyObject *
-stringio_closed(stringio *self, void *context)
+stringio_closed_impl(stringio *self, void *context)
 {
     CHECK_INITIALIZED(self);
     return PyBool_FromLong(self->closed);
 }
 
 static PyObject *
-stringio_line_buffering(stringio *self, void *context)
+stringio_closed(stringio *self, void *context)
+{
+    PyObject *result;
+    Py_BEGIN_CRITICAL_SECTION(self);
+    result = stringio_closed_impl(self, context);
+    Py_END_CRITICAL_SECTION();
+    return result;
+}
+
+static PyObject *
+stringio_line_buffering_impl(stringio *self, void *context)
 {
     CHECK_INITIALIZED(self);
     CHECK_CLOSED(self);
@@ -956,18 +997,35 @@ stringio_line_buffering(stringio *self, void *context)
 }
 
 static PyObject *
-stringio_newlines(stringio *self, void *context)
+stringio_line_buffering(stringio *self, void *context)
+{
+    PyObject *result;
+    Py_BEGIN_CRITICAL_SECTION(self);
+    result = stringio_line_buffering_impl(self, context);
+    Py_END_CRITICAL_SECTION();
+    return result;
+}
+
+static PyObject *
+stringio_newlines_impl(stringio *self, void *context)
 {
     CHECK_INITIALIZED(self);
     CHECK_CLOSED(self);
-    if (self->decoder == NULL)
+    if (self->decoder == NULL) {
         Py_RETURN_NONE;
+    }
     return PyObject_GetAttr(self->decoder, &_Py_ID(newlines));
 }
 
-#define clinic_state() (find_io_state_by_def(Py_TYPE(self)))
-#include "clinic/stringio.c.h"
-#undef clinic_state
+static PyObject *
+stringio_newlines(stringio *self, void *context)
+{
+    PyObject *result;
+    Py_BEGIN_CRITICAL_SECTION(self);
+    result = stringio_newlines_impl(self, context);
+    Py_END_CRITICAL_SECTION();
+    return result;
+}
 
 static struct PyMethodDef stringio_methods[] = {
     _IO_STRINGIO_CLOSE_METHODDEF
@@ -983,8 +1041,8 @@ static struct PyMethodDef stringio_methods[] = {
     _IO_STRINGIO_READABLE_METHODDEF
     _IO_STRINGIO_WRITABLE_METHODDEF
 
-    {"__getstate__", (PyCFunction)stringio_getstate, METH_NOARGS},
-    {"__setstate__", (PyCFunction)stringio_setstate, METH_O},
+    _IO_STRINGIO___GETSTATE___METHODDEF
+    _IO_STRINGIO___SETSTATE___METHODDEF
     {NULL, NULL}        /* sentinel */
 };