refleak test failure in test_exceptions

[iritkatriel]

BPO	44895
Nosy	@gvanrossum, @vstinner, @cjerdonek, @ambv, @markshannon, @corona10, @pablogsal, @miss-islington, @iritkatriel
PRs	bpo-44895: Temporarily add an extra gc.collect() call #27746 [3.10] bpo-44895: Temporarily add an extra gc.collect() call (GH-27746) #27753 bpo-44895: skip test_no_hang_on_context_chain_cycle2 until the reflea… #27761 bpo-44895: Introduce PYTHONDUMPREFSFILE variable for refcount dumping #27767 [3.10] bpo-44895: skip test_no_hang_on_context_chain_cycle2 until the refleak is fixed (GH-27761) #27778 bpo-44895: libregrtest: refleak check clears types later #28113
Files	cpython-1628938551.dump.gz refleak.py strict_refleak_check.patch

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2021-08-12.00:13:38.919>
labels = ['interpreter-core', '3.10', '3.11']
title = 'refleak test failure in test_exceptions'
updated_at = <Date 2021-09-01.16:43:27.187>
user = 'https://github.com/iritkatriel'

bugs.python.org fields:

activity = <Date 2021-09-01.16:43:27.187>
actor = 'vstinner'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Interpreter Core']
creation = <Date 2021-08-12.00:13:38.919>
creator = 'iritkatriel'
dependencies = []
files = ['50216', '50224', '50251']
hgrepos = []
issue_num = 44895
keywords = ['patch']
message_count = 71.0
messages = ['399424', '399449', '399450', '399451', '399452', '399453', '399456', '399457', '399459', '399463', '399472', '399485', '399492', '399507', '399510', '399513', '399516', '399517', '399533', '399537', '399539', '399540', '399541', '399542', '399543', '399546', '399554', '399555', '399556', '399557', '399560', '399578', '399588', '399589', '399601', '399636', '399639', '399676', '399681', '399682', '399696', '399697', '399700', '399703', '399739', '399740', '399762', '399764', '399781', '399785', '399786', '399788', '399789', '399792', '399794', '399795', '399796', '399800', '399855', '399856', '399857', '400645', '400741', '400757', '400779', '400794', '400840', '400844', '400848', '400853', '400854']
nosy_count = 9.0
nosy_names = ['gvanrossum', 'vstinner', 'chris.jerdonek', 'lukasz.langa', 'Mark.Shannon', 'corona10', 'pablogsal', 'miss-islington', 'iritkatriel']
pr_nums = ['27746', '27753', '27761', '27767', '27778', '28113']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue44895'
versions = ['Python 3.10', 'Python 3.11']

Linked PRs

• gh-89058: remove skip from test_no_hang_on_context_chain_cycle2 #102903

[iritkatriel]

For background see https://bugs.python.org/issue33930#msg399403

iritkatriel@Irits-MBP cpython % repeat 10 ./python.exe -m test -R 3:3 test_exceptions -m test_no_hang_on_context_chain_cycle2 -m test_recursion_normalizing_infinite_exception -m test_recursion_in_except_handler -m test_recursion_normalizing_with_no_memory
0:00:00 load avg: 2.32 Run tests sequentially
0:00:00 load avg: 2.32 [1/1] test_exceptions
beginning 6 repetitions
123456
......

== Tests result: SUCCESS ==

1 test OK.

Total duration: 5.9 sec
Tests result: SUCCESS
0:00:00 load avg: 2.22 Run tests sequentially
0:00:00 load avg: 2.22 [1/1] test_exceptions
beginning 6 repetitions
123456
......

== Tests result: SUCCESS ==

1 test OK.

Total duration: 5.8 sec
Tests result: SUCCESS
0:00:00 load avg: 2.20 Run tests sequentially
0:00:00 load avg: 2.20 [1/1] test_exceptions
beginning 6 repetitions
123456
......

== Tests result: SUCCESS ==

1 test OK.

Total duration: 5.8 sec
Tests result: SUCCESS
0:00:00 load avg: 2.17 Run tests sequentially
0:00:00 load avg: 2.17 [1/1] test_exceptions
beginning 6 repetitions
123456
......
test_exceptions leaked [6, 6, 4] references, sum=16
test_exceptions leaked [6, 6, 4] memory blocks, sum=16
test_exceptions failed (reference leak)

== Tests result: FAILURE ==

1 test failed:
test_exceptions

1 re-run test:
test_exceptions

Total duration: 5.9 sec
Tests result: FAILURE
0:00:00 load avg: 2.08 Run tests sequentially
0:00:00 load avg: 2.08 [1/1] test_exceptions
beginning 6 repetitions
123456
......
test_exceptions leaked [6, 6, 6] references, sum=18
test_exceptions leaked [6, 6, 6] memory blocks, sum=18
test_exceptions failed (reference leak)

== Tests result: FAILURE ==

1 test failed:
test_exceptions

1 re-run test:
test_exceptions

Total duration: 5.8 sec
Tests result: FAILURE
0:00:00 load avg: 2.39 Run tests sequentially
0:00:00 load avg: 2.39 [1/1] test_exceptions
beginning 6 repetitions
123456
......
test_exceptions leaked [6, 6, 6] references, sum=18
test_exceptions leaked [6, 6, 6] memory blocks, sum=18
test_exceptions failed (reference leak)

== Tests result: FAILURE ==

1 test failed:
test_exceptions

1 re-run test:
test_exceptions

Total duration: 6.0 sec
Tests result: FAILURE
0:00:00 load avg: 2.36 Run tests sequentially
0:00:00 load avg: 2.36 [1/1] test_exceptions
beginning 6 repetitions
123456
......
test_exceptions leaked [6, 6, 6] references, sum=18
test_exceptions leaked [6, 6, 6] memory blocks, sum=18
test_exceptions failed (reference leak)

== Tests result: FAILURE ==

1 test failed:
test_exceptions

1 re-run test:
test_exceptions

Total duration: 6.0 sec
Tests result: FAILURE
0:00:00 load avg: 2.31 Run tests sequentially
0:00:00 load avg: 2.31 [1/1] test_exceptions
beginning 6 repetitions
123456
......

== Tests result: SUCCESS ==

1 test OK.

Total duration: 6.3 sec
Tests result: SUCCESS
0:00:00 load avg: 2.20 Run tests sequentially
0:00:00 load avg: 2.20 [1/1] test_exceptions
beginning 6 repetitions
123456
......
test_exceptions leaked [6, 6, 6] references, sum=18
test_exceptions leaked [6, 6, 6] memory blocks, sum=18
test_exceptions failed (reference leak)

== Tests result: FAILURE ==

1 test failed:
test_exceptions

1 re-run test:
test_exceptions

Total duration: 6.1 sec
Tests result: FAILURE
0:00:00 load avg: 2.35 Run tests sequentially
0:00:00 load avg: 2.35 [1/1] test_exceptions

[vstinner]

I fail to reproduce the issue on Linux on the 3.10 branch. I interrupted the job after 20 minutes:

$ ./python -m test -R 3:3 test_exceptions -m test_no_hang_on_context_chain_cycle2 -m test_recursion_normalizing_infinite_exception -m test_recursion_in_except_handler -m test_recursion_normalizing_with_no_memory -F -j1
(...)
0:21:38 load avg: 2.01 [134] test_exceptions passed
beginning 6 repetitions
123456
......

I tested the commit 5d44443.

[iritkatriel]

I see it on Mac but not windows.

Running the test with -v or adding prints makes the leak go away. I’m suspecting that one of the recursion tests fails to clear an exception or something like that.

Removing any one of the tests makes it stop failing.

[iritkatriel]

Victor, if the …cycle2 test is hanging then you need the change in PR27626.

[vstinner]

I am not more lucky in the main branch. I ran it for 30 minutes and it didn't fail.

$ ./python -m test -R 3:3 test_exceptions -m test_no_hang_on_context_chain_cycle2 -m test_recursion_normalizing_infinite_exception -m test_recursion_in_except_handler -m test_recursion_normalizing_with_no_memory -F -j1
(...)
0:31:15 load avg: 1.88 [184] test_exceptions passed
beginning 6 repetitions
123456
......
^C
Kill <TestWorkerProcess #1 running test=test_exceptions pid=173796 time=4.2 sec> process group

== Tests result: INTERRUPTED ==
Test suite interrupted by signal SIGINT.

184 tests OK.

Total duration: 31 min 19 sec
Tests result: INTERRUPTED

I tested commit 8ac0886.

[vstinner]

Victor, if the …cycle2 test is hanging then you need the change in PR27626.

That's the commit d5c2174. My main branch is up to date (commit 8ac0886), it includes the commit d5c2174.

[iritkatriel]

I don't know why you need to kill it. It's not a long test.

[vstinner]

I see it on Mac but not windows.

Aha, maybe there is something specific on Mac which triggers an exact code path to trigger to bug. I already saw bugs like that.

You can try to play with gc.set_threshold() to change how garbage collection is triggered.

[iritkatriel]

I don't know why you need to kill it. It's not a long test.

Ah I see, -F.

[iritkatriel]

The problem disappears if I add a gc.collect() loop at the beginning of the new test:

diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index 79798ecf05..e0aeac9d10 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -1014,6 +1014,7 @@ def cycle():
 
     def test_no_hang_on_context_chain_cycle2(self):
         # See issue 25782. Cycle at head of context chain.
+        while gc.collect(): pass
 
         class A(Exception):
             pass

[iritkatriel]

This fails (test_recursion_normalizing_with_no_memory is not needed):

./python.exe -m test -R 3:3 test_exceptions -m test_no_hang_on_context_chain_cycle2 -m test_recursion_normalizing_infinite_exception -m test_recursion_in_except_handler