Description

assignee = None
closed_at = <Date 2017-11-10.21:05:15.294>
created_at = <Date 2017-11-08.04:27:27.470>
labels = ['interpreter-core', '3.7', 'type-crash']
title = 'Segfault when closing BufferedWriter from a different thread'
updated_at = <Date 2017-11-10.21:05:15.294>
user = 'https://github.com/benfogle'

activity = <Date 2017-11-10.21:05:15.294>
actor = 'pitrou'
assignee = 'none'
closed = True
closed_date = <Date 2017-11-10.21:05:15.294>
closer = 'pitrou'
components = ['Interpreter Core']
creation = <Date 2017-11-08.04:27:27.470>
creator = 'benfogle'
dependencies = []
files = []
hgrepos = []
issue_num = 31976
keywords = ['patch']
message_count = 3.0
messages = ['305803', '306048', '306049']
nosy_count = 5.0
nosy_names = ['pitrou', 'benjamin.peterson', 'stutzbach', 'martin.panter', 'benfogle']
pr_nums = ['4331']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue31976'
versions = ['Python 3.7']

Activity

1. benfogle commented on Nov 8, 2017

   

   benfoglemannequin

   on Nov 8, 2017

   MannequinAuthor

   More actions

   To reproduce:

   import threading
   import io
   import time
   import _pyio
   
   class MyFileIO(io.FileIO):
       def flush(self):
           # Simulate a slow flush. Slow disk, etc.
           time.sleep(0.25)
           super().flush()
   
   raw = MyFileIO('test.dat', 'wb')
   #fp = _pyio.BufferedWriter(raw)
   fp = io.BufferedWriter(raw)
   t1 = threading.Thread(target=fp.close)
   t1.start()
   time.sleep(0.1) # Ensure t1 is sleeping in fp.close()/raw.flush()
   fp.write(b'test')
   t1.join()
   

   _pyio.BufferedWriter ignores the error completely rather than throwing a ValueError("write to closed file").
2. benfogle

   added

   3.7 (EOL)end of lifeend of life

   interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)

   type-crashA hard crash of the interpreter, possibly with a core dumpA hard crash of the interpreter, possibly with a core dump

   on Nov 8, 2017
3. pitrou commented on Nov 10, 2017

   

   pitrou

   on Nov 10, 2017

   Member

   More actions

   New changeset 9703f09 by Antoine Pitrou (benfogle) in branch 'master':
   bpo-31976: Fix race condition when flushing a file is slow. (bpo-4331)
   9703f09
4. pitrou commented on Nov 10, 2017

   

   pitrou

   on Nov 10, 2017

   Member

   More actions

   Thank you for posting this Benjamin. As I said on the PR, I don't think I want to backport this to 3.6, as it is always delicate to reason about subclassing and threads.
5. pitrou

   closed this as completedon Nov 10, 2017
6. ezio-melotti

   transferred this issue fromon Apr 10, 2022
7. cmaloney

   added a commit that references this issue on May 14, 2026

   exp: Introduce Nibbler in _pyio.BufferedWriter

   ff824fb

Issue actions