[2.7] test_io: race condition in test_interrupted_write_text() (test_io hangs on x86 Gentoo Refleaks 2.7) #75912

vstinner · 2017-10-09T07:13:26Z

BPO	31731
Nosy	@vstinner, @zware, @miss-islington
PRs	[2.7] bpo-31731: test_io hangs with --huntrleaks: exclude it #7459 bpo-31731: Fix test_io.check_interrupted_write() #11225 [3.7] bpo-31731: Fix test_io.check_interrupted_write() (GH-11225) #11226

^{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 = <Date 2018-12-18.22:57:04.637>
created_at = <Date 2017-10-09.07:13:25.905>
labels = ['tests']
title = '[2.7] test_io: race condition in test_interrupted_write_text() (test_io hangs on x86 Gentoo Refleaks 2.7)'
updated_at = <Date 2018-12-18.23:10:49.894>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2018-12-18.23:10:49.894>
actor = 'miss-islington'
assignee = 'none'
closed = True
closed_date = <Date 2018-12-18.22:57:04.637>
closer = 'vstinner'
components = ['Tests']
creation = <Date 2017-10-09.07:13:25.905>
creator = 'vstinner'
dependencies = []
files = []
hgrepos = []
issue_num = 31731
keywords = ['patch']
message_count = 16.0
messages = ['303924', '303925', '304879', '318111', '318121', '318783', '318785', '318786', '318788', '318859', '318860', '319158', '332093', '332096', '332098', '332099']
nosy_count = 3.0
nosy_names = ['vstinner', 'zach.ware', 'miss-islington']
pr_nums = ['7459', '11225', '11226']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue31731'
versions = ['Python 2.7']

vstinner · 2017-10-09T07:13:25Z

test_io is running since longer than 5 hours on x86 Gentoo Refleaks 2.7:

http://buildbot.python.org/all/#/builders/78/builds/1/steps/4/logs/stdio

2:12:11 load avg: 3.26 [402/403] test_contains passed -- running: test_io (1739 sec)
beginning 6 repetitions
123456
......
running: test_io (1769 sec)
running: test_io (1799 sec)
(...)
running: test_io (19529 sec)

http://buildbot.python.org/all/#/builders/78/builds/1/steps/4/logs/stdio

vstinner · 2017-10-09T07:14:58Z

I interrupted the build.

vstinner · 2017-10-24T09:13:29Z

test_io was blocked a second time:

http://buildbot.python.org/all/#/builders/78/builds/3

running: test_io (68517 sec)
running: test_io (68547 sec)
running: test_io (68577 sec)
command interrupted, attempting to kill
process killed by signal 9
program finished with exit code -1
elapsedTime=69935.628661

vstinner · 2018-05-29T21:58:02Z

I didn't see the failure recently. I close the issue.

zware · 2018-05-29T22:10:07Z

test_io is currently hung on that builder:

buildbot 13541 0.0 0.1 4920 2508 pts/1 Ss+ May28 0:00 \_ make buildbottest TESTOPTS=-j2 -R 3:3 -u-cpu TESTPYTHONOPTS= TESTTIMEOUT=11700
buildbot 13556 0.2 0.4 33620 9952 pts/1 Sl+ May28 2:45 | \_ ./python -Wd -3 -E -tt -R ./Lib/test/regrtest.py -uall --slowest -rwW -j2 -R 3:3 -u-cpu
buildbot 28750 0.0 1.1 65412 24428 pts/1 S+ May28 0:54 | \_ /buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/python -E -3 -R -Wd -m test.regrtest --slaveargs [["test_io", 0, false], {"match_tests": null, "pgo": false, "huntrleaks": [3, 3, "reflog.txt"], "failfast": false, "use_resources": ["audio", "curses", "largefile", "network", "bsddb", "decimal", "subprocess", "urlfetch", "gui", "xpickle"]}]

vstinner · 2018-06-05T21:43:03Z

I succeeded to attach gdb to a regrtest slave process stuck in test_io... but somehow attaching the process into gdb unblocked the process... and the test completed.

Sadly, the first time that I attached the process, I forgot to allow a directory to load python-gdb.py. So I had to detach and attach again the process to get a working "py-bt" command. Maybe this action unblocked Python. It's hard to say.

(gdb) py-bt
Traceback (most recent call first):
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/_pyio.py", line 1126, in _flush_unlocked
    def _flush_unlocked(self):
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/_pyio.py", line 1104, in write
    self._flush_unlocked()
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/_pyio.py", line 1302, in write
    return BufferedWriter.write(self, b)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/test/test_io.py", line 1186, in check_writes
    self.assertEqual(bufio.write(contents[n:n+size]), size)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/test/test_io.py", line 1723, in test_writes_and_peek
    self.check_writes(_peek)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/unittest/case.py", line 329, in run
    testMethod()
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/unittest/case.py", line 393, in __call__
    return self.run(*args, **kwds)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/unittest/suite.py", line 108, in run
    test(result)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/unittest/suite.py", line 70, in __call__
    return self.run(*args, **kwds)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/unittest/suite.py", line 108, in run
    test(result)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/unittest/suite.py", line 70, in __call__
    return self.run(*args, **kwds)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/test/support/__init__.py", line 1461, in run
    test(result)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/test/support/__init__.py", line 1535, in _run_suite
    result = runner.run(suite)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/test/support/__init__.py", line 1626, in run_unittest
    _run_suite(suite)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/test/test_io.py", line 3367, in test_main
    support.run_unittest(*tests)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/test/regrtest.py", line 1361, in run_the_test
    indirect_test()
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/test/regrtest.py", line 1375, in dash_R
    run_the_test()
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/test/regrtest.py", line 1239, in runtest_inner
    huntrleaks)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/test/regrtest.py", line 1044, in runtest
    return runtest_inner(test, verbose, quiet, huntrleaks, pgo, testdir)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/test/regrtest.py", line 513, in main
    result = runtest(*args, **kwargs)
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/test/regrtest.py", line 2025, in main_in_temp_cwd
    main()
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/test/regrtest.py", line 2038, in <module>
    main_in_temp_cwd()
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)

(gdb) where
#0 0x0050b6fd in PyEval_EvalFrameEx (
f=Frame 0xb6bd1634, for file /buildbot/buildarea/2.7.ware-gentoo-x86.refleak/build/Lib/pyio.py, line 1126, in _flush_unlocked (self=<BufferedRandom(raw=<PyMockRawIO(write_stack=['\x00', '\x01', '\x02', '\x03', '\x04', '\x05', '\x06', '\x07', '\x08', '\t', '\n', '\x0b', '\x0c', '\r', '\x0e', '\x0f\x10', '\x11\x12', '\x13\x14', '\x15\x16', '\x17\x18', '\x19\x1a', '\x1b\x1c', '\x1d\x1e', '\x1f ', '!"', '#$', '%&', "'(", ')*', '+,', '-./', '012', '345', '678', '9:;', '<=>', '?@A', 'BCD', 'EFG', 'HIJ', 'KLM', 'NOP', 'QRS', 'TUV', 'WXY', 'Z[\\]', '^`a', 'bcde', 'fghi', 'jklm', 'nopq', 'rstu', 'vwxy', 'z{|}', '~\x7f\x80\x81', '\x82\x83\x84\x85', '\x86\x87\x88\x89', '\x8a\x8b\x8c\x8d', '\x8e\x8f\x90\x91', '\x92\x93\x94\x95', '\x96\x97\x98\x99\x9a', '\x9b\x9c\x9d\x9e\x9f', '\xa0\xa1\xa2\xa3\xa4', '\xa5\xa6\xa7\xa8\xa9', '\xaa\xab\xac\xad\xae', '\xaf\xb0\xb1\xb2\xb3', '\xb4\xb5\xb6\xb7\xb8', '\xb9\xba\xbb\xbc\xbd', '\xbe\xbf\xc0\xc1\xc2', '\xc3\xc4\xc5\xc6\xc7', '\xc8\xc9\xca\xcb\xcc', '\xcd\xce\xcf\xd0\xd1', '\xd2\x...(truncated),
throwflag=0) at Python/ceval.c:1094
#1 0x0051a9e8 in PyEval_EvalCodeEx (co=0xb6ccdda8,
globals={'BufferedReader': <ABCMeta(abc_cache=<WeakSet(data=set([<weakref at remote 0xb6c21434>, <weakref at remote 0xb6bcc8b4>]), _pending_removals=[], _remove=<function at remote 0xb6687c64>, _iterating=set([])) at remote 0xb668a4cc>, peek=<function at remote 0xb6687ad4>, _abc_negative_cache_version=26, tell=<function at remote 0xb6687bc4>, read=<function at remote 0xb6687a34>, __doc=u'BufferedReader(raw[, buffer_size])\n\n A buffer for a readable, sequential BaseRawIO object.\n\n The constructor creates a BufferedReader for the given readable raw\n stream and buffer_size. If buffer_size is omitted, DEFAULT_BUFFER_SIZE\n is used.\n ', __init_=<function at remote 0xb6687994>, _reset_read_buf=<function at remote 0xb66879e4>, _abc_negative_cache=<WeakSet(data=set([]), _pending_removals=[], _remove=<function at remote 0xb66b7da4>, _iterating=set([])) at remote 0xb668a0a4>, __module__='_pyio', __abstractmethods__=frozenset([]), _peek_unlocked=<function at remote 0xb6687b24>, _read_unlocked=<function a...(truncated),
locals=0x0, args=0xb6c1cb50, argcount=1, kws=0xb6c1cb54, kwcount=0, defs=0x0, defcount=0, closure=0x0) at Python/ceval.c:3604
#2 0x0051d618 in fast_function (func=<function at remote 0xb6687e94>, pp_stack=0xbfbcc660, n=1, na=1, nk=0) at Python/ceval.c:4467
#3 0x0051d283 in call_function (pp_stack=0xbfbcc660, oparg=0) at Python/ceval.c:4392
(...)

vstinner · 2018-06-05T22:17:56Z

Hum, I succeeded to reproduce a hang in test_io using the command:

buildbot@stormageddon ~/python27 $ ./python -m test -v -m 'test_interrupted*' -F test_io
(...)
0:04:38 load avg: 3.36 [ 44] test_io
test_interrupted_write_buffered (test.test_io.CSignalsTest) ... ok
test_interrupted_write_text (test.test_io.CSignalsTest) ... ok
test_interrupted_write_unbuffered (test.test_io.CSignalsTest) ... ok
test_interrupted_write_buffered (test.test_io.PySignalsTest) ... ok
test_interrupted_write_text (test.test_io.PySignalsTest) ... ok
test_interrupted_write_unbuffered (test.test_io.PySignalsTest) ... ok

----------------------------------------------------------------------
Ran 6 tests in 6.167s

OK
0:04:45 load avg: 3.65 [ 45] test_io
test_interrupted_write_buffered (test.test_io.CSignalsTest) ... ok
test_interrupted_write_text (test.test_io.CSignalsTest) ... ok
test_interrupted_write_unbuffered (test.test_io.CSignalsTest) ... ok
test_interrupted_write_buffered (test.test_io.PySignalsTest) ... ok
test_interrupted_write_text (test.test_io.PySignalsTest) ...
***

Traces in gdb of the stuck process:

***
(gdb) py-bt
Traceback (most recent call first):
  Waiting for the GIL
  <built-in method acquire of thread.lock object at remote 0xb6c09258>
  File "/buildbot/python27/Lib/threading.py", line 340, in wait
    waiter.acquire()
  File "/buildbot/python27/Lib/threading.py", line 940, in join
    self.__block.wait()
  File "/buildbot/python27/Lib/test/test_io.py", line 3161, in check_interrupted_write
    t.join()
  File "/buildbot/python27/Lib/test/test_io.py", line 3186, in test_interrupted_write_text
    self.check_interrupted_write("xy", b"xy", mode="w", encoding="ascii")
  File "/buildbot/python27/Lib/unittest/case.py", line 329, in run
    testMethod()
  File "/buildbot/python27/Lib/unittest/case.py", line 393, in __call__
    return self.run(*args, **kwds)
  File "/buildbot/python27/Lib/unittest/suite.py", line 108, in run
    test(result)
  File "/buildbot/python27/Lib/unittest/suite.py", line 70, in __call__
    return self.run(*args, **kwds)
  File "/buildbot/python27/Lib/unittest/suite.py", line 108, in run
    test(result)
  File "/buildbot/python27/Lib/unittest/suite.py", line 70, in __call__
    return self.run(*args, **kwds)
  File "/buildbot/python27/Lib/unittest/runner.py", line 151, in run
    test(result)
  File "/buildbot/python27/Lib/test/support/__init__.py", line 1535, in _run_suite
    result = runner.run(suite)
  File "/buildbot/python27/Lib/test/support/__init__.py", line 1626, in run_unittest
    _run_suite(suite)
  File "/buildbot/python27/Lib/test/test_io.py", line 3367, in test_main
    support.run_unittest(*tests)
  File "/buildbot/python27/Lib/test/regrtest.py", line 1236, in runtest_inner
    indirect_test()
  File "/buildbot/python27/Lib/test/regrtest.py", line 1044, in runtest
    return runtest_inner(test, verbose, quiet, huntrleaks, pgo, testdir)
  File "/buildbot/python27/Lib/test/regrtest.py", line 837, in local_runtest
    testdir=testdir)
  File "/buildbot/python27/Lib/test/regrtest.py", line 851, in main
    result = local_runtest()
  File "/buildbot/python27/Lib/test/regrtest.py", line 2025, in main_in_temp_cwd
    main()
  File "/buildbot/python27/Lib/test/__main__.py", line 3, in <module>
    regrtest.main_in_temp_cwd()
  File "/buildbot/python27/Lib/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/buildbot/python27/Lib/runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)

(gdb) info threads
Id Target Id Frame

1 Thread 0xb7518700 (LWP 14442) "python" 0xb7772b49 in __kernel_vsyscall ()
2 Thread 0xb6b36b40 (LWP 18865) "python" 0xb7772b49 in __kernel_vsyscall ()

(gdb) t 2
[Switching to thread 2 (Thread 0xb6b36b40 (LWP 18865))]
#0 0xb7772b49 in __kernel_vsyscall ()

(gdb) py-bt
Traceback (most recent call first):
  <built-in function read>
  File "/buildbot/python27/Lib/test/test_io.py", line 3141, in _read
    s = os.read(r, 1)
  File "/buildbot/python27/Lib/threading.py", line 754, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/buildbot/python27/Lib/threading.py", line 801, in __bootstrap_inner
    self.run()
  File "/buildbot/python27/Lib/threading.py", line 774, in __bootstrap
    self.__bootstrap_inner()
***

And now I recall how much I hate this test. It made me crazy in Python 2 for a long time.

This specific test was my motiviation to add signal.pthread_sigmask() to Python 3.3.

Note: I also implemented the PEP-475 in Python 3.5 to make Python more reliable when getting signals.

vstinner · 2018-06-05T22:27:44Z

Sadly, issues with test_io.test_interrupted*() are old. See for example the bpo-23680.

Two years ago, Martin Panter saw test_io.test_interrupted_write_text() hangs on Python 3.6 and on AMD64 FreeBSD 9.x 3.5:
https://bugs.python.org/issue22331#msg266688
https://bugs.python.org/issue22331#msg266725

Martin proposed a fix using signal.pthread_kill() rather than scheduling a SIGALRM signal in 1 second, but the fix was not merged and I closed the issue since I didn't see the issue recently.

vstinner · 2018-06-05T22:59:32Z

buildbot@stormageddon ~/python27 $ ./python -m test -v -m 'test_interrupted*' -F test_io

I'm unable to reproduce this issue on my Fedora 28 laptop (Linux kernel 4.16.11-300.fc28.x86_64). In the previous message, I reproduced the issue directly on Zach's Gentoo buildbot builder.

vstinner · 2018-06-06T21:33:38Z

New changeset 02b4d67 by Victor Stinner in branch '2.7':
bpo-31731: test_io hangs with --huntrleaks: exclude it (GH-7459)
02b4d67

vstinner · 2018-06-06T21:35:32Z

test_io hangs often on Gentoo Refleaks 2.7 buildbot: Zachary Ware, who owns the builder, has to interrupt the test regularly. So I disabled test_io in regrtest when --huntrleaks is used, since at least one bug has been identified in test_io in test_interrupted*().

vstinner · 2018-06-09T16:54:25Z

AMD64 FreeBSD 10.x Shared 3.7 issue:

http://buildbot.python.org/all/#/builders/124/builds/380

0:15:14 load avg: 0.18 [415/415/1] test_io crashed (Exit code 1)
Timeout (0:15:00)!
Thread 0x0000000806943c00 (most recent call first):
File "/usr/home/buildbot/python/3.7.koobs-freebsd10/build/Lib/test/test_io.py", line 4090 in _read
File "/usr/home/buildbot/python/3.7.koobs-freebsd10/build/Lib/threading.py", line 865 in run
File "/usr/home/buildbot/python/3.7.koobs-freebsd10/build/Lib/threading.py", line 917 in _bootstrap_inner
File "/usr/home/buildbot/python/3.7.koobs-freebsd10/build/Lib/threading.py", line 885 in _bootstrap

Thread 0x0000000802006400 (most recent call first):
File "/usr/home/buildbot/python/3.7.koobs-freebsd10/build/Lib/threading.py", line 1048 in _wait_for_tstate_lock
File "/usr/home/buildbot/python/3.7.koobs-freebsd10/build/Lib/threading.py", line 1032 in join
File "/usr/home/buildbot/python/3.7.koobs-freebsd10/build/Lib/test/test_io.py", line 4111 in check_interrupted_write
File "/usr/home/buildbot/python/3.7.koobs-freebsd10/build/Lib/test/test_io.py", line 4135 in test_interrupted_write_text

vstinner · 2018-12-18T22:36:41Z

AMD64 FreeBSD 10.x Shared 3.7 issue:

I wrote PR 11225 which may fix it.

vstinner · 2018-12-18T22:52:43Z

New changeset 05c9d31 by Victor Stinner in branch 'master':
bpo-31731: Fix test_io.check_interrupted_write() (GH-11225)
05c9d31

vstinner · 2018-12-18T22:57:05Z

The test can be fixed in Python 2.7 by exposing pthread_sigmask() somehow, or at least pthread_sigmask(SIG_BLOCK, [SIGALARM]), but honestly, I don't think that it's worth it. The test only very rarely hangs, and the bug has already been fixed in Python 3.

I close the issue. I fixed a race condition in test_io of Python 3. (The bot will shortly backport the fix to 3.7).

miss-islington · 2018-12-18T23:10:50Z

New changeset 729fc5d by Miss Islington (bot) in branch '3.7':
bpo-31731: Fix test_io.check_interrupted_write() (GH-11225)
729fc5d

vstinner added the tests Tests in the Lib/test dir label Oct 9, 2017

vstinner changed the title ~~test_io hangs on~~ [2.7] test_io hangs on x86 Gentoo Refleaks 2.7 Oct 9, 2017

vstinner closed this as completed May 29, 2018

zware reopened this May 29, 2018

vstinner changed the title ~~[2.7] test_io hangs on x86 Gentoo Refleaks 2.7~~ [2.7] test_io: race condition in test_interrupted_write_text() (test_io hangs on x86 Gentoo Refleaks 2.7) Jun 20, 2018

vstinner closed this as completed Dec 18, 2018

ezio-melotti transferred this issue from another repository Apr 10, 2022

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[2.7] test_io: race condition in test_interrupted_write_text() (test_io hangs on x86 Gentoo Refleaks 2.7) #75912

[2.7] test_io: race condition in test_interrupted_write_text() (test_io hangs on x86 Gentoo Refleaks 2.7) #75912

vstinner commented Oct 9, 2017

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miss-islington commented Dec 18, 2018

[2.7] test_io: race condition in test_interrupted_write_text() (test_io hangs on x86 Gentoo Refleaks 2.7) #75912

[2.7] test_io: race condition in test_interrupted_write_text() (test_io hangs on x86 Gentoo Refleaks 2.7) #75912

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vstinner commented Oct 9, 2017

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miss-islington commented Dec 18, 2018