[pypy-issue] [issue1283] A waiting stdin.read() in a thread + stdin.close() in another thread = the latter freezes

[Jan Kaliszewski]

New submission from Jan Kaliszewski <zuo at chopin.edu.pl>:

I encountered this behaviour when tried using multiprocessing.Process() when there was 
a waiting stdin.read() in some thread.

A simple example -- which worked well under CPython 2.7, but freezes under PyPy 1.9 -- 
follows:

from multiprocessing import Process
from threading import Thread
import sys

def f():
    while True:
        sys.stdin.read()

def g():
    print 'Process ok'

t = Thread(target=f)
t.daemon = True
t.start()

p = Process(target=g)
p.start()
p.join()

The problem is caused by sys.stdint.close() in multiprocessing.Process._bootstrap 
(file 'lib-python/2.7/multiprocessing/process.py, line #249).

But then I realized that it is not multiprocessing/fork-specific issue.

Simply any waiting stdin.read() + stdin.close() in another thread causes that thread 
to freeze (under PyPy, not under CPython), e.g.:


import sys
from threading import Thread

def f():
    while True:
        try:
            sys.stdin.read()
        except:
            return

def f2():
    sys.stdin.close()
    print 'All right'

t = Thread(target=f)
t.daemon = True
t.start()

t2 = Thread(target=f2)
t2.start()

t2.join()

----------
messages: 4832
nosy: pypy-issue, zuo
priority: bug
release: 1.9
status: unread
title: A waiting stdin.read() in a thread + stdin.close() in another thread = the latter freezes

________________________________________
PyPy bug tracker <tracker at bugs.pypy.org>
<https://bugs.pypy.org/issue1283>
________________________________________