[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Antoine Pitrou]

Antoine Pitrou  added the comment:

Turns out this didn't fix all possible situations. See bpo-43406 for an updated 
patch.

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Marcin Gozdalik]

Marcin Gozdalik  added the comment:

A program which failed under Python 3.6 with

TypeError: 'int' object is not callable

still fails under Python 3.7.4 with same exception:

import signal
import os
import sys
import time

import multiprocessing

def fail():
def handler(*args):
pass

while True:
signal.signal(signal.SIGUSR1, signal.SIG_IGN)
signal.signal(signal.SIGUSR1, handler)

proc = multiprocessing.Process(target=fail)
proc.start()
time.sleep(1)
pid = proc.pid

i = 0
try:
while proc.is_alive():
print("\r", end='')
print(i, end='')
i += 1
os.kill(pid, signal.SIGUSR1)
time.sleep(0.001)
finally:
proc.join()

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Antoine Pitrou]

Change by Antoine Pitrou :


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

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[miss-islington]

miss-islington  added the comment:


New changeset 310f414bbd4d6ed1d8813f724c91ce9b4129c0ba by Miss Islington (bot) 
in branch '3.7':
bpo-23395: Fix PyErr_SetInterrupt if the SIGINT signal is ignored or not 
handled (GH-7778)
https://github.com/python/cpython/commit/310f414bbd4d6ed1d8813f724c91ce9b4129c0ba


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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[miss-islington]

Change by miss-islington :


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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Antoine Pitrou]

Antoine Pitrou  added the comment:

It's just a bugfix to avoid a rogue exception.  It sounds gratuitous to add 
markers for bug fixes in the documentation.

--
versions: +Python 3.7, Python 3.8 -Python 2.7, Python 3.5

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[STINNER Victor]

STINNER Victor  added the comment:

The interrupt_main() documentation needs a "versionchanged:: 3.8" to document 
that the behavior changed in Python 3.8, no? (do nothing if the signal is not 
handled by Python).

I'm not comfortable to backport this change. I suggest to only change Python 
3.8 (master branch).

While reviewing this change, I found code which should be refactored: see 
bpo-37031.

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Antoine Pitrou]

Antoine Pitrou  added the comment:


New changeset 608876b6b1eb59538e6c29671a733033fb8b5be7 by Antoine Pitrou (Matěj 
Cepl) in branch 'master':
bpo-23395: Fix PyErr_SetInterrupt if the SIGINT signal is ignored or not 
handled (GH-7778)
https://github.com/python/cpython/commit/608876b6b1eb59538e6c29671a733033fb8b5be7


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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Matej Cepl]

Change by Matej Cepl :


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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Matej Cepl]

Change by Matej Cepl :


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stage:  -> patch review

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Matej Cepl]

Change by Matej Cepl :


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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Wataru Matsumoto]

Wataru Matsumoto added the comment:

Recently I've encountered the similar problem.
I found the case that SIGINT signal is ignored(set as SIG_IGN) due to the 
external reason.
If the python program starts background in bash script, bash set SIGINT as 
SIG_IGN.

test_interrupt.py
import _thread
_thread.interrupt_main()

run.sh
#!/bin/bash
python test_interrupt.py &
sleep 1s

./run.sh 
Traceback (most recent call last):
  File "test_interrupt.py", line 2, in 
_thread.interrupt_main()
RuntimeError: the SIGINT signal is ignored
(it was TypeError: 'int' object is not callable before the patch)

Python mapped default_int_handler to SIG_INT on SIG_DFL in PyInit__signal.
As the python developer can't control how the program is started, it may be 
better to setup default_int_handler regardless the handler type.

And initially SIG_INT is mapped to default_int_handler but once signal.signal 
is called, the mapping is lost even though the SIG_DFL is specified.
It may need to handle SIG_INT specially in signal_signal_impl as well to keep 
the consistent behavior.

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Wataru Matsumoto]

Changes by Wataru Matsumoto :


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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[STINNER Victor]

STINNER Victor added the comment:

> It seems to be against the current HEAD -- is there a chance that this will 
> be backported to 2.7 (which is what I need to use)?

Yes, I will fix Python 2.7 and 3.5, I will just make 
PyErr_SetInterruptWithErr() private (rename to _PyErr_SetInterruptWithErr()).

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Andre Merzky]

Andre Merzky added the comment:

I can confirm that the patch provided by Victor addresses the problem.  It 
seems to be against the current HEAD -- is there a chance that this will be 
backported to 2.7 (which is what I need to use)?

Thanks!  Andre.

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[STINNER Victor]

STINNER Victor added the comment:

Attached interrupt_main.patch fixes for _thread.interrupt_main(): raise an 
exception if the SIGINT signal is ignored (SIG_IGN) or not handled by Python 
(SIG_DFL).

My patch updates the documentation and addds unit tests.

issue23395.2.patch looks wrong: it's not the right place to handle the error.

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Added file: http://bugs.python.org/file43560/interrupt_main.patch

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Andre Merzky]

Andre Merzky added the comment:

It seems you were right, that needed a DecRef indeed: the IncRef is already 
called on construction.  The DecRef for the result also needed fixing - an 
updated patch is attached.

--
Added file: http://bugs.python.org/file43546/issue23395.2.patch

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Andre Merzky]

Andre Merzky added the comment:

thanks for looking into this!  And also, thanks for the details in the original 
bug report -- I found this by chance, after unsuccessfully banging my head 
against this very problem for quite a while! 

I am not sure if the DecRef needs to be called really if the arglist is not 
stored or passed on.  But thanks for pointing that out, I'll check if I can 
find where the corresponding IncRef is called (assuming that happens somewhere).

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Thomas Kluyver]

Thomas Kluyver added the comment:

Does Py_DECREF(arglist); need to be called in all cases? I'm genuinely unsure, 
as I don't usually work on C code, but my guess would be that it does.

I'm not sure whether review is now done on Github.

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Andre Merzky]

Andre Merzky added the comment:

Attached is a patch which seems to resolve the issue for me -- this now 
triggers the expected `KeyboardInterrupt` in the main thread.  For verification 
one can run the unaltered code as provided by Thomas.

I would very much appreciate feedback, to make sure that the semantics is 
actually what one would expect.  The patch is against the 2.7 branch from 
https://github.com/python/cpython.git, and I did not test it against any other 
branch.

I also opened a pull request (https://github.com/python/cpython/pull/39).

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keywords: +patch
Added file: http://bugs.python.org/file43544/issue23395.patch

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Andre Merzky]

Andre Merzky added the comment:

Thanks Thomas.

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Thomas Kluyver]

Thomas Kluyver added the comment:

It's waiting for someone to make a patch - I'm no longer running into it, so 
it's not high on my priority list. Given that it's been over a year since I 
created this issue, it's probably not about to get fixed unless you've got some 
time to work on it.

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Andre Merzky]

Changes by Andre Merzky :


--
versions: +Python 2.7

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Andre Merzky]

Andre Merzky added the comment:

Thanks for the PingBack, Thomas.

I am not very familiar with the Python community approach to bug reports, so 
can someone comment if that is worth waiting for to get fixed, or is it that a 
rather futile hope without providing a patch myself?  I don't think I currently 
have the resources to dig into the details...

Thanks, Andre.

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Thomas Kluyver]

Thomas Kluyver added the comment:

As far as I know it has not been fixed.

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Andre Merzky]

Andre Merzky added the comment:

Did anything ever come of this?  I also frequently stumble over that error -- 
but alas not in a debug setting, but on actual running code... :/

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Thomas Kluyver]

New submission from Thomas Kluyver:

In tracking down an obscure error we were seeing, we boiled it down to this 
test case for thread.interrupt_main():

import signal, threading, _thread, time
signal.signal(signal.SIGINT, signal.SIG_DFL) # or SIG_IGN

def thread_run():
_thread.interrupt_main()

t = threading.Thread(target=thread_run)
t.start()
time.sleep(10)

This fails with an error message TypeError: 'int' object is not callable, and 
a traceback completely disconnected from the cause of the error, presumably 
because it's not coming from the usual Python stack.

The problem appears to be that interrupt_main sets (in the C code) 
Handlers[SIGINT].tripped, which is only expected to occur when the handler is a 
Python function. When PyErr_CheckSignals() runs, it tries to call 
Handlers[SIGINT].func as a Python function, but it's a Python integer, causing 
the error.

I think the fix for this is to check what Handlers[sig_num].func is, either in 
trip_signal() before setting Handlers[sig_num].tripped, or in 
PyErr_CheckSignals before calling it. I can work on a patch if desired, but I'm 
not brilliant at C.

--
components: Library (Lib)
messages: 235412
nosy: minrk, takluyver
priority: normal
severity: normal
status: open
title: _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN
type: behavior
versions: Python 3.5

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[issue23395] _thread.interrupt_main() errors if SIGINT handler in SIG_DFL, SIG_IGN

[Antoine Pitrou]

Changes by Antoine Pitrou pit...@free.fr:


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nosy: +haypo, neologix

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