[issue42717] The python interpreter crashed with "_enter_buffered_busy"

[Mark Shannon]

Mark Shannon  added the comment:

Please leave the issue open. This is a real bug.

It may not be fixed right now, but that doesn't mean it won't ever be fixed.

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nosy: +Mark.Shannon

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[issue42717] The python interpreter crashed with "_enter_buffered_busy"

[Xinmeng Xia]

Xinmeng Xia  added the comment:

It seems that this bug won't be fixed. Should this issue be closed now?

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[issue42717] The python interpreter crashed with "_enter_buffered_busy"

[Xinmeng Xia]

Xinmeng Xia  added the comment:

Thank you for your patient reply. I see now. Hoping that some one can figure 
out a good idea to fix this problem.

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[issue42717] The python interpreter crashed with "_enter_buffered_busy"

[Steve Stagg]

Steve Stagg  added the comment:

It's one of those ugly multithreading issues that's really hard to reason about 
unfortunately.

In this case, it's not the size of the loop so much as you've discovered a way 
to make it very likely that the background thread is doing IO (and holding the 
IO lock) during shutdown.

Here's an example that reproduces the abort for me (again, it's multithreading, 
so you may have a different experience) with a smaller range value:

---
import sys, threading

def run():
for i in range(100):
sys.stderr.write(' =.= ' * 1)

if __name__ == '__main__':
threading.Thread(target=run, daemon=True).start()
---

The problem with daemon threads is that they get killed fairly suddenly and 
without much ability to correct bad state during shutdown, so any fix here 
would likely be around re-visiting the thread termination code as linked in the 
issue above.

There may be a fix possible, but it's going to be a complex thread state 
management fix, not just a limit on loop counts, unfortunately

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[issue42717] The python interpreter crashed with "_enter_buffered_busy"

[Xinmeng Xia]

Xinmeng Xia  added the comment:

Could we try to limit the number of thread or state or something? I mean if we 
set parameter of "range", for example, to 1000 or less here, the crash will no 
longer happen. I think the parser can not handle too heavy loop so that it 
crashes.

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[issue42717] The python interpreter crashed with "_enter_buffered_busy"

[Steve Stagg]

Steve Stagg  added the comment:

I think the problem here is that the issue can only really be detected late on 
during interpreter shutdown.

This makes recovery very hard to do.  Plus the thread termination has left 
shared state in an unmanaged condition, so it's super dangerous to re-enter 
python again

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[issue42717] The python interpreter crashed with "_enter_buffered_busy"

[Xinmeng Xia]

Xinmeng Xia  added the comment:

Thanks for your kind explanation! Now, I have understand the causes of this 
core dump. Considering it will not cause core dump in Python 2.x, I am 
wondering should we suggest an exception to catch it rather than "core dump"?

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[issue42717] The python interpreter crashed with "_enter_buffered_busy"

[Steve Stagg]

Steve Stagg  added the comment:

Minimal test case:


import sys, threading

def run():
for i in range(1000):
sys.stderr.write(' =.= ')

if __name__ == '__main__':
threading.Thread(target=run, daemon=True).start()
===

I think this is expected behaviour.  My knowledge isn't complete here, but 
something similar to:

* During shutdown, the daemon threads are aborted
* In your example, the thread is very likely to be busy doing IO, so holding 
the io lock.
* The abort you're seeing is an explicit check/abort to avoid a deadlock 
(https://bugs.python.org/issue23309).

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nosy: +stestagg

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[issue42717] The python interpreter crashed with "_enter_buffered_busy"

[Xinmeng Xia]

New submission from Xinmeng Xia :

The following program can work well in Python 2. However it crashes in Python 
3( 3.6-3.10 ) with the following error messages.
Program:

import sys,time, threading

class test:
def test(self):
pass


class test1:
def run(self):
for i in range(0,1000):
connection = test()
sys.stderr.write(' =_= ')


def testrun():
client = test1()
thread = threading.Thread(target=client.run, args=())
thread.setDaemon(True)
thread.start()

time.sleep(0.1)

testrun()


Error message:
--

=_=  =_=  =_=  =_=  =_=  ..  =_=  =_=  =_=  =_= 
Fatal Python error: _enter_buffered_busy: could not acquire lock for 
<_io.BufferedWriter name=''> at interpreter shutdown, possibly due to 
daemon threads
Python runtime state: finalizing (tstate=0xd0c180)

Current thread 0x7f08a638f700 (most recent call first):

Aborted (core dumped)
--

When I remove "time.sleep(0.1)" or  "thread.setDaemon(True)" or 
"sys.stderr.write(' =_= ')" or "for i in range(0,1000)":, the python 
interpreter seems to work well.

--
components: Interpreter Core
messages: 383582
nosy: xxm
priority: normal
severity: normal
status: open
title: The python interpreter crashed with "_enter_buffered_busy"
type: crash
versions: Python 3.10

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