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Revert "bpo-31356: Add context manager to temporarily disable GC #4224 #5495

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Revert "bpo-31356: Add context manager to temporarily disable GC (GH-…
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28 changes: 0 additions & 28 deletions Doc/library/gc.rst
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Expand Up @@ -33,34 +33,6 @@ The :mod:`gc` module provides the following functions:
Disable automatic garbage collection.


.. class:: ensure_disabled()

Return a context manager object that disables the garbage collector and reenables the previous
state upon completion of the block. This is basically equivalent to::

from gc import enable, disable, isenabled

@contextmanager
def ensure_disabled():
was_enabled_previously = isenabled()
gc.disable()
yield
if was_enabled_previously:
gc.enable()

And lets you write code like this::

with ensure_disabled():
run_some_timing()

with ensure_disabled():
# do_something_that_has_real_time_guarantees
# such as a pair trade, robotic braking, etc

without needing to explicitly enable and disable the garbage collector yourself.
This context manager is implemented in C to assure atomicity, thread safety and speed.


.. function:: isenabled()

Returns true if automatic collection is enabled.
Expand Down
1 change: 0 additions & 1 deletion Include/internal/mem.h
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Expand Up @@ -116,7 +116,6 @@ struct _gc_runtime_state {

int enabled;
int debug;
long disabled_threads;
/* linked lists of container objects */
struct gc_generation generations[NUM_GENERATIONS];
PyGC_Head *generation0;
Expand Down
71 changes: 1 addition & 70 deletions Lib/test/test_gc.py
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@@ -1,16 +1,14 @@
import unittest
from test.support import (verbose, refcount_test, run_unittest,
strip_python_stderr, cpython_only, start_threads,
temp_dir, requires_type_collecting,reap_threads)
temp_dir, requires_type_collecting)
from test.support.script_helper import assert_python_ok, make_script

import sys
import time
import gc
import weakref
import threading
import warnings


try:
from _testcapi import with_tp_del
Expand Down Expand Up @@ -1009,73 +1007,6 @@ def __del__(self):
# empty __dict__.
self.assertEqual(x, None)

def test_ensure_disabled(self):
original_status = gc.isenabled()

with gc.ensure_disabled():
inside_status = gc.isenabled()

after_status = gc.isenabled()
self.assertEqual(original_status, True)
self.assertEqual(inside_status, False)
self.assertEqual(after_status, True)

def test_ensure_disabled_with_gc_disabled(self):
gc.disable()

original_status = gc.isenabled()

with gc.ensure_disabled():
inside_status = gc.isenabled()

after_status = gc.isenabled()
self.assertEqual(original_status, False)
self.assertEqual(inside_status, False)
self.assertEqual(after_status, False)

@reap_threads
def test_ensure_disabled_thread(self):

thread_original_status = None
thread_inside_status = None
thread_after_status = None

def disabling_thread():
nonlocal thread_original_status
nonlocal thread_inside_status
nonlocal thread_after_status
thread_original_status = gc.isenabled()

with gc.ensure_disabled():
time.sleep(0.01)
thread_inside_status = gc.isenabled()

thread_after_status = gc.isenabled()

original_status = gc.isenabled()

with warnings.catch_warnings(record=True) as w, gc.ensure_disabled():
inside_status_before_thread = gc.isenabled()
thread = threading.Thread(target=disabling_thread)
thread.start()
inside_status_after_thread = gc.isenabled()

after_status = gc.isenabled()
thread.join()

self.assertEqual(len(w), 1)
self.assertTrue(issubclass(w[-1].category, RuntimeWarning))
self.assertEqual("Garbage collector enabled while another thread is "
"inside gc.ensure_enabled", str(w[-1].message))
self.assertEqual(original_status, True)
self.assertEqual(inside_status_before_thread, False)
self.assertEqual(thread_original_status, False)
self.assertEqual(thread_inside_status, True)
self.assertEqual(thread_after_status, False)
self.assertEqual(inside_status_after_thread, False)
self.assertEqual(after_status, True)


def test_main():
enabled = gc.isenabled()
gc.disable()
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11 changes: 0 additions & 11 deletions Misc/NEWS.d/3.7.0b1.rst
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Expand Up @@ -196,17 +196,6 @@ by Sanyam Khurana.

..

.. bpo: 31356
.. date: 2017-11-02-00-34-42
.. nonce: 54Lb8U
.. section: Core and Builtins

Add a new contextmanager to the gc module that temporarily disables the GC
and restores the previous state. The implementation is done in C to assure
atomicity and speed.

..

.. bpo: 31179
.. date: 2017-08-10-17-32-48
.. nonce: XcgLYI
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2018-02-02-08-50-46.bpo-31356.MNwUOQ.rst
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@@ -0,0 +1,2 @@
Remove the new API added in bpo-31356 (gc.ensure_disabled() context
manager).
106 changes: 0 additions & 106 deletions Modules/gcmodule.c
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Expand Up @@ -1067,10 +1067,6 @@ static PyObject *
gc_enable_impl(PyObject *module)
/*[clinic end generated code: output=45a427e9dce9155c input=81ac4940ca579707]*/
{
if(_PyRuntime.gc.disabled_threads){
PyErr_WarnEx(PyExc_RuntimeWarning, "Garbage collector enabled while another "
"thread is inside gc.ensure_enabled",1);
}
_PyRuntime.gc.enabled = 1;
Py_RETURN_NONE;
}
Expand Down Expand Up @@ -1512,102 +1508,6 @@ static PyMethodDef GcMethods[] = {
{NULL, NULL} /* Sentinel */
};

typedef struct {
PyObject_HEAD
int previous_gc_state;
} ensure_disabled_object;


static void
ensure_disabled_object_dealloc(ensure_disabled_object *m_obj)
{
Py_TYPE(m_obj)->tp_free((PyObject*)m_obj);
}

static PyObject *
ensure_disabled__enter__method(ensure_disabled_object *self, PyObject *args)
{
PyGILState_STATE gstate = PyGILState_Ensure();
++_PyRuntime.gc.disabled_threads;
self->previous_gc_state = _PyRuntime.gc.enabled;
gc_disable_impl(NULL);
PyGILState_Release(gstate);
Py_RETURN_NONE;
}

static PyObject *
ensure_disabled__exit__method(ensure_disabled_object *self, PyObject *args)
{
PyGILState_STATE gstate = PyGILState_Ensure();
--_PyRuntime.gc.disabled_threads;
if(self->previous_gc_state){
gc_enable_impl(NULL);
}else{
gc_disable_impl(NULL);
}
PyGILState_Release(gstate);
Py_RETURN_NONE;
}



static struct PyMethodDef ensure_disabled_object_methods[] = {
{"__enter__", (PyCFunction) ensure_disabled__enter__method, METH_NOARGS},
{"__exit__", (PyCFunction) ensure_disabled__exit__method, METH_VARARGS},
{NULL, NULL} /* sentinel */
};

static PyObject *
new_disabled_obj(PyTypeObject *type, PyObject *args, PyObject *kwdict){
ensure_disabled_object *self;
self = (ensure_disabled_object *)type->tp_alloc(type, 0);
return (PyObject *) self;
};

static PyTypeObject gc_ensure_disabled_type = {
PyVarObject_HEAD_INIT(NULL, 0)
"gc.ensure_disabled", /* tp_name */
sizeof(ensure_disabled_object), /* tp_size */
0, /* tp_itemsize */
/* methods */
(destructor) ensure_disabled_object_dealloc,/* tp_dealloc */
0, /* tp_print */
0, /* tp_getattr */
0, /* tp_setattr */
0, /* tp_reserved */
0, /* tp_repr */
0, /* tp_as_number */
0, /*tp_as_sequence*/
0, /*tp_as_mapping*/
0, /*tp_hash*/
0, /*tp_call*/
0, /*tp_str*/
PyObject_GenericGetAttr, /*tp_getattro*/
0, /*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /*tp_flags*/
0, /*tp_doc*/
0, /* tp_traverse */
0, /* tp_clear */
0, /* tp_richcompare */
0, /* tp_weaklistoffset */
0, /* tp_iter */
0, /* tp_iternext */
ensure_disabled_object_methods, /* tp_methods */
0, /* tp_members */
0, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
0, /* tp_init */
PyType_GenericAlloc, /* tp_alloc */
new_disabled_obj, /* tp_new */
PyObject_Del, /* tp_free */
};


static struct PyModuleDef gcmodule = {
PyModuleDef_HEAD_INIT,
"gc", /* m_name */
Expand Down Expand Up @@ -1648,12 +1548,6 @@ PyInit_gc(void)
if (PyModule_AddObject(m, "callbacks", _PyRuntime.gc.callbacks) < 0)
return NULL;

if (PyType_Ready(&gc_ensure_disabled_type) < 0)
return NULL;
if (PyModule_AddObject(m, "ensure_disabled", (PyObject*) &gc_ensure_disabled_type) < 0)
return NULL;


#define ADD_INT(NAME) if (PyModule_AddIntConstant(m, #NAME, NAME) < 0) return NULL
ADD_INT(DEBUG_STATS);
ADD_INT(DEBUG_COLLECTABLE);
Expand Down