[issue38195] A bug in the multiprocessing module

[eshkrig]

eshkrig  added the comment:

$ cat /etc/os-release
NAME=Gentoo
ID=gentoo
PRETTY_NAME="Gentoo/Linux"
ANSI_COLOR="1;32"
HOME_URL="https://www.gentoo.org/";
SUPPORT_URL="https://www.gentoo.org/support/";
BUG_REPORT_URL="https://bugs.gentoo.org/";

$ uname -a
Linux lynx 5.16.2-gentoo-1 #1 SMP PREEMPT Fri Jan 21 10:38:04 MSK 2022 x86_64 
AMD FX(tm)-8350 Eight-Core Processor AuthenticAMD GNU/Linux

$ python --version
Python 3.9.9

$ ./testqueue.py
queue.get() from pid 11371
queue.get() from pid 11372
^CTraceback (most recent call last):
  File "/home/john/main/123/./testqueue.py", line 45, in 
result = ps_queues[cpu].get(timeout=2)
  File "/usr/lib/python3.9/multiprocessing/queues.py", line 117, in get
res = self._recv_bytes()
  File "/usr/lib/python3.9/multiprocessing/connection.py", line 221, in 
recv_bytes
buf = self._recv_bytes(maxlength)
  File "/usr/lib/python3.9/multiprocessing/connection.py", line 426, in 
_recv_bytes
return self._recv(size)
  File "/usr/lib/python3.9/multiprocessing/connection.py", line 384, in _recv
chunk = read(handle, remaining)
KeyboardInterrupt

--
resolution: out of date -> 
status: closed -> open
versions: +Python 3.9 -Python 3.6

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[issue38195] A bug in the multiprocessing module

[eshkrig]

New submission from eshkrig :

Hi!

I found a bug in the multiprocessing module.

The documentation (https://docs.python.org/3.6/library/multiprocessing.html) 
for the Queue.get method says:
"If timeout is a positive number, it blocks at most timeout seconds ..."

But the Queue.get method freezes if the process filling the queue terminates 
while reading data.

In the attachment is an example of a program (testqueue.py) that freezes after 
~ 5-30 seconds.
After pressing -, the output is as follows:
Traceback (most recent call last):
  File "./testqueue.py", line 45, in 
result = ps_queues[cpu].get(timeout=2)
  File "/usr/lib64/python3.6/multiprocessing/queues.py", line 108, in get
res = self._recv_bytes()
  File "/usr/lib64/python3.6/multiprocessing/connection.py", line 216, in 
recv_bytes
buf = self._recv_bytes(maxlength)
  File "/usr/lib64/python3.6/multiprocessing/connection.py", line 411, in 
_recv_bytes
return self._recv(size)
  File "/usr/lib64/python3.6/multiprocessing/connection.py", line 379, in _recv
chunk = read(handle, remaining)
KeyboardInterrupt

Please fix it.

--
components: Extension Modules
files: testqueue.py
messages: 352613
nosy: eshkrig
priority: normal
severity: normal
status: open
title: A bug in the multiprocessing module
type: behavior
versions: Python 3.6
Added file: https://bugs.python.org/file48609/testqueue.py

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