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/usr/lib/python3/dist-packages/twisted/internet/

/usr/lib/python3/dist-packages/twisted/internet

Name	Size	Mode	Actions
iocpreactor/	-	0755	rm
test/	-	0755	rm
__pycache__/	-	0755	rm
abstract.py	19274	0644	edit dl rm
address.py	5246	0644	edit dl rm
asyncioreactor.py	10553	0644	edit dl rm
base.py	44260	0644	edit dl rm
cfreactor.py	17501	0644	edit dl rm
default.py	1942	0644	edit dl rm
defer.py	71193	0644	edit dl rm
endpoints.py	77207	0644	edit dl rm
epollreactor.py	8493	0644	edit dl rm
error.py	12645	0644	edit dl rm
fdesc.py	3223	0644	edit dl rm
gireactor.py	6123	0644	edit dl rm
glib2reactor.py	1115	0644	edit dl rm
gtk2reactor.py	3614	0644	edit dl rm
gtk3reactor.py	2252	0644	edit dl rm
inotify.py	14691	0644	edit dl rm
interfaces.py	96515	0644	edit dl rm
kqreactor.py	10292	0644	edit dl rm
main.py	1054	0644	edit dl rm
pollreactor.py	6026	0644	edit dl rm
posixbase.py	26357	0644	edit dl rm
process.py	38896	0644	edit dl rm
protocol.py	27134	0644	edit dl rm
pyuisupport.py	817	0644	edit dl rm
reactor.py	1863	0644	edit dl rm
selectreactor.py	6215	0644	edit dl rm
serialport.py	2317	0644	edit dl rm
ssl.py	8444	0644	edit dl rm
stdio.py	1045	0644	edit dl rm
task.py	31119	0644	edit dl rm
tcp.py	54908	0644	edit dl rm
threads.py	3953	0644	edit dl rm
tksupport.py	2045	0644	edit dl rm
udp.py	18569	0644	edit dl rm
unix.py	21965	0644	edit dl rm
utils.py	7876	0644	edit dl rm
win32eventreactor.py	15193	0644	edit dl rm
wxreactor.py	5263	0644	edit dl rm
wxsupport.py	1363	0644	edit dl rm
_baseprocess.py	1913	0644	edit dl rm
_dumbwin32proc.py	13107	0644	edit dl rm
_glibbase.py	12813	0644	edit dl rm
_idna.py	1397	0644	edit dl rm
_newtls.py	9332	0644	edit dl rm
_pollingfile.py	8982	0644	edit dl rm
_posixserialport.py	1995	0644	edit dl rm
_posixstdio.py	4687	0644	edit dl rm
_producer_helpers.py	3788	0644	edit dl rm
_resolver.py	8530	0644	edit dl rm
_signals.py	2718	0644	edit dl rm
_sslverify.py	71770	0644	edit dl rm
_threadedselect.py	11764	0644	edit dl rm
_win32serialport.py	4744	0644	edit dl rm
_win32stdio.py	3204	0644	edit dl rm
__init__.py	521	0644	edit dl rm

Edit: /usr/lib/python3/dist-packages/twisted/internet/_signals.py (2718B)

# -*- test-case-name: twisted.internet.test.test_sigchld -*-
# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
This module is used to integrate child process termination into a
reactor event loop.  This is a challenging feature to provide because
most platforms indicate process termination via SIGCHLD and do not
provide a way to wait for that signal and arbitrary I/O events at the
same time.  The naive implementation involves installing a Python
SIGCHLD handler; unfortunately this leads to other syscalls being
interrupted (whenever SIGCHLD is received) and failing with EINTR
(which almost no one is prepared to handle).  This interruption can be
disabled via siginterrupt(2) (or one of the equivalent mechanisms);
however, if the SIGCHLD is delivered by the platform to a non-main
thread (not a common occurrence, but difficult to prove impossible),
the main thread (waiting on select() or another event notification
API) may not wake up leading to an arbitrary delay before the child
termination is noticed.

The basic solution to all these issues involves enabling SA_RESTART
(ie, disabling system call interruption) and registering a C signal
handler which writes a byte to a pipe.  The other end of the pipe is
registered with the event loop, allowing it to wake up shortly after
SIGCHLD is received.  See L{twisted.internet.posixbase._SIGCHLDWaker}
for the implementation of the event loop side of this solution.  The
use of a pipe this way is known as the U{self-pipe
trick<http://cr.yp.to/docs/selfpipe.html>}.

From Python version 2.6, C{signal.siginterrupt} and C{signal.set_wakeup_fd}
provide the necessary C signal handler which writes to the pipe to be
registered with C{SA_RESTART}.
"""

from __future__ import division, absolute_import

import signal

def installHandler(fd):
    """
    Install a signal handler which will write a byte to C{fd} when
    I{SIGCHLD} is received.

This is implemented by installing a SIGCHLD handler that does nothing,
    setting the I{SIGCHLD} handler as not allowed to interrupt system calls,
    and using L{signal.set_wakeup_fd} to do the actual writing.

@param fd: The file descriptor to which to write when I{SIGCHLD} is
        received.
    @type fd: C{int}
    """
    if fd == -1:
        signal.signal(signal.SIGCHLD, signal.SIG_DFL)
    else:
        def noopSignalHandler(*args):
            pass
        signal.signal(signal.SIGCHLD, noopSignalHandler)
        signal.siginterrupt(signal.SIGCHLD, False)
    return signal.set_wakeup_fd(fd)

def isDefaultHandler():
    """
    Determine whether the I{SIGCHLD} handler is the default or not.
    """
    return signal.getsignal(signal.SIGCHLD) == signal.SIG_DFL

cmd: