[issue36109] test_descr fails on AMD64 Windows8 3.x buildbots

[Pablo Galindo Salgado]

Pablo Galindo Salgado  added the comment:

A lot of buildbots were failing for this test so a lot of them will become 
green after ff3d39faa8aa28308cc5eae6843eaac514da8fd8.

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[issue36109] test_descr fails on AMD64 Windows8 3.x buildbots

[Pablo Galindo Salgado]

Change by Pablo Galindo Salgado :


--
resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue36109] test_descr fails on AMD64 Windows8 3.x buildbots

[Pablo Galindo Salgado]

Pablo Galindo Salgado  added the comment:


New changeset ff3d39faa8aa28308cc5eae6843eaac514da8fd8 by Pablo Galindo (Serhiy 
Storchaka) in branch 'master':
bpo-36109: Fix random test_descr failure. (GH-12044)
https://github.com/python/cpython/commit/ff3d39faa8aa28308cc5eae6843eaac514da8fd8


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[issue36109] test_descr fails on AMD64 Windows8 3.x buildbots

[Pablo Galindo Salgado]

Pablo Galindo Salgado  added the comment:

Ok, actually this turns to be much easier: Sometimes __eq__ was also called 
twice but now as we use PyDict_GetItemWithError instead of PyDict_GetItem, if 
the extra __eq__ happens as a consequence of a dict lookup the error is ignored 
so that was the reason the test was not failing before.

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[issue36109] test_descr fails on AMD64 Windows8 3.x buildbots

[Pablo Galindo Salgado]

Pablo Galindo Salgado  added the comment:

Although 12044 fixes the problem, something a bit more fundamental may have 
changed. I have spent time investigating why this is happening and the problem 
is that in the line:


self.assertEqual(c.attr, 1)

Evil.__eq__ is invoked twice where before it was only invoked once. This does 
not happen all the time, and it seems to only happen under some combination of 
hashes in the class dictionary, being the extra __eq__ invocation a check for 
equality when looking up attr in the c object. When the test succeeds, the 
extra check is not done (and therefore the attribute is not deleted). I think 
this happens because some identity is used to check when doing the lookup 
(comparing the pointers) but I would like to understand exactly how the hash is 
influencing the different code paths to be sure that nothing important has 
changed recently.

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[issue36109] test_descr fails on AMD64 Windows8 3.x buildbots

[Pablo Galindo Salgado]

Pablo Galindo Salgado  added the comment:

Although PR12004 fixes the problem, something a bit more fundamental may have 
changed. I have spent time investigating why this is happening and the problem 
is that in the line:


self.assertEqual(c.attr, 1)

Evil.__eq__ is invoked twice where before it was only invoked once. This does 
not happen all the time, and it seems to only happen under some combination of 
hashes in the class dictionary, being the extra __eq__ invocation a check for 
equality when looking up attr in the c object. When the test succeeds, the 
extra check is not done (and therefore the attribute is not deleted). I think 
this happens because some identity is used to check when doing the lookup 
(comparing the pointers) but I would like to understand exactly how the hash is 
influencing the different code paths to be sure that nothing important has 
changed recently.

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[issue36109] test_descr fails on AMD64 Windows8 3.x buildbots

[Pablo Galindo Salgado]

Change by Pablo Galindo Salgado :


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Removed message: https://bugs.python.org/msg336608

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[issue36109] test_descr fails on AMD64 Windows8 3.x buildbots

[Serhiy Storchaka]

Change by Serhiy Storchaka :


--
keywords: +patch
pull_requests: +12070
stage:  -> patch review

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[issue36109] test_descr fails on AMD64 Windows8 3.x buildbots

[Pablo Galindo Salgado]

Pablo Galindo Salgado  added the comment:

It seems that this is a race condition created as a consequence of:

https://github.com/python/cpython/pull/2/files

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nosy: +serhiy.storchaka

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[issue36109] test_descr fails on AMD64 Windows8 3.x buildbots

[Pablo Galindo Salgado]

Pablo Galindo Salgado  added the comment:

I can reproduce this locally. How has this not being spotted by the CI:

❯ ./python.exe -m test test_descr
Run tests sequentially
0:00:00 load avg: 3.82 [1/1] test_descr
test test_descr failed -- Traceback (most recent call last):
  File "/Users/pgalindo3/github/cpython/Lib/test/test_descr.py", line 4341, in 
test_vicious_descriptor_nonsense
self.assertEqual(c.attr, 1)
  File "/Users/pgalindo3/github/cpython/Lib/test/test_descr.py", line 4328, in 
__eq__
del C.attr
AttributeError: attr

test_descr failed

== Tests result: FAILURE ==

1 test failed:
test_descr

Total duration: 2 sec 437 ms
Tests result: FAILURE

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[issue36109] test_descr fails on AMD64 Windows8 3.x buildbots

[Pablo Galindo Salgado]

New submission from Pablo Galindo Salgado :

https://buildbot.python.org/all/#/builders/32/builds/2198

==
ERROR: test_vicious_descriptor_nonsense 
(test.test_descr.ClassPropertiesAndMethods)
--
Traceback (most recent call last):
  File "D:\buildarea\3.x.bolen-windows8\build\lib\test\test_descr.py", line 
4341, in test_vicious_descriptor_nonsense
self.assertEqual(c.attr, 1)
  File "D:\buildarea\3.x.bolen-windows8\build\lib\test\test_descr.py", line 
4328, in __eq__
del C.attr
AttributeError: attr
--
Ran 140 tests in 7.836s

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components: Tests, Windows
messages: 336554
nosy: pablogsal, paul.moore, steve.dower, tim.golden, zach.ware
priority: normal
severity: normal
status: open
title: test_descr fails on AMD64 Windows8 3.x buildbots
versions: Python 3.8

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