X-Recipient:	archive-cygwin AT delorie DOT com
DomainKey-Signature:	a=rsa-sha1; c=nofws; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:from:to:subject:date:message-id:references
	:in-reply-to:content-type:content-id:content-transfer-encoding
	:mime-version; q=dns; s=default; b=jqmYdg5WUFkuR9JIYrk93wyIp+E4u
	GeIyN8f5HtmMj8zY04wy6YtvYgQYWZfxOs/aONs15lL1z9bvp0ZlEPIAdmy2wO8Z
	L7J/WqlmuZ+aA5mZZcEMewnNhSutjsF7PGFgEogHrWtHe+RfuPAP/oTcA6R3t7SY
	jEWTftHxjh9tfw=
DKIM-Signature:	v=1; a=rsa-sha1; c=relaxed; d=sourceware.org; h=list-id
	:list-unsubscribe:list-subscribe:list-archive:list-post
	:list-help:sender:from:to:subject:date:message-id:references
	:in-reply-to:content-type:content-id:content-transfer-encoding
	:mime-version; s=default; bh=62ewAWSj3zU19zQDMQeK5py5nJI=; b=Lcv
	1+Atzlfmnn4RKi8p/I5MWXm8/krqqh9vpNh7ilablmPiqf/aqnVnIMszktqviYa9
	nPGyL3ibFVwwVG54dNhf264TC1ZGBzpIetyJ4IK1X61bHCWEQIhjUkhtp2yCEBhi
	8l8ED3xuqysoUTBLHA0OSFDioUwmv1OkSF26t3W4=
Mailing-List:	contact cygwin-help AT cygwin DOT com; run by ezmlm
List-Id:	<cygwin.cygwin.com>
List-Subscribe:	<mailto:cygwin-subscribe AT cygwin DOT com>
List-Archive:	<http://sourceware.org/ml/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-help AT cygwin DOT com>, <http://sourceware.org/ml/#faqs>
Sender:	cygwin-owner AT cygwin DOT com
Mail-Followup-To:	cygwin AT cygwin DOT com
Delivered-To:	mailing list cygwin AT cygwin DOT com
Authentication-Results:	sourceware.org; auth=none
X-Spam-SWARE-Status:	No, score=-1.9 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_NONE,SPF_HELO_PASS,SPF_PASS autolearn=ham version=3.3.1 spammy=HX-Languages-Length:2722, Running, race, gift
X-HELO:	NAM03-CO1-obe.outbound.protection.outlook.com
ARC-Seal:	i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=OyZZ1jG33uGx/kd36/3xWuSzfShcdNWkP3LrRhdLrHmiYpVyR2de/iKwh5c7PcinjSECMmd0gq9CdQQ8tyVZ1SmYn3R2X8ZjU6RfXhZmJOSK/rbZV1FMZ+LpPBdLZp96r0MiQZXuYMaT0eDCgATEC/DrNiPUSWxdNBvf2o6xhomQXmtkWcAaCSp1QVNv6rnNNFaBiU2Ks7eRxghed7kBgaxAHiM85MVWFI+1DOii4sNQlK1RHDXwv/Ys8i8S4+Ac1EzycfEWmhay3g8B2gywjlBbE14pkavt+9T8WhIUjBU++5Qpxoih7tTyfLYSs+ulLvixwAxVJtj9v5OI8ntbng==
ARC-Message-Signature:	i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=U1omgcApPEkMTJ1M0XzWu/sa6HcBpHtjz+yh19OCkek=; b=TsnPuhlugkIMh8MZMEBVGuZExdZ9541nBRis0/qk5+g2+Qwo7y64qeGydU9NXEB4kQ4BZoPSzkGsRbuSVTTvxYyfhw73062IeTtcSbxErirQy+0P3PlC7stYI9I2yQdWIberJHfgi65+KIo5ZklEM3SD5A20CitgH3v4gRN2dpmtqUfkRNxhjs6D+OduL0OM0H5LLY4pVGkzgFjdHFt8ilGMgPwzIIBc1SPiTD0mkpPsBX4CJRxkSjaDNCFDjwdj/hyKkANGN2QacS9DZZOTfhd621m+qj8fEMB30LYNC6ZkIaZlFgQtgIy9TEtSTkMXJ6nkTH8dVE3mUJcZRFP4Mw==
ARC-Authentication-Results:	i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=cornell.edu; dmarc=pass action=none header.from=cornell.edu; dkim=pass header.d=cornell.edu; arc=none
DKIM-Signature:	v=1; a=rsa-sha256; c=relaxed/relaxed; d=cornell.edu; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=U1omgcApPEkMTJ1M0XzWu/sa6HcBpHtjz+yh19OCkek=; b=fJAfCW2hMiWIe3ED2PHfvPZZiuDFnan3Qxe86aP67rOqlmebp1vzW+IkElvMOxGKhmWhBDWtqZzH7/VktaUOMC6EqffhVOvD0HfMwzXqK61AclqHZoIsTGGPoeKtDQfbCla0YdHzsXRF+BZACarSh3eEqSeuVZV2D4brwEmyQe8=
From:	Ken Brown <kbrown AT cornell DOT edu>
To:	"cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>
Subject:	Re: ssh-agent doesn't die
Date:	Fri, 4 Oct 2019 14:27:00 +0000
Message-ID:	<801bca17-2c61-bb6a-f02c-c4912232d9c5@cornell.edu>
References:	<319e26c0-32f0-40b7-2137-c7de170a3486 AT rl DOT ac DOT uk> <5b225738-c2d7-fbfe-48a7-8c2a38c3398c AT cornell DOT edu> <0ccd17b6-c22a-1a18-9409-1ebcfae60868 AT huarp DOT harvard DOT edu> <9f7a14bb-f81b-c566-bb84-8da7fc6d0fad AT cornell DOT edu> <185c5774-dd8b-5488-b818-4cec5a24bf2d AT cornell DOT edu>
In-Reply-To:	<185c5774-dd8b-5488-b818-4cec5a24bf2d@cornell.edu>
user-agent:	Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0
authentication-results:	spf=none (sender IP is ) smtp.mailfrom=kbrown AT cornell DOT edu;
x-ms-oob-tlc-oobclassifiers:	OLM:9508;
received-spf:	None (protection.outlook.com: cornell.edu does not designate permitted sender hosts)
x-ms-exchange-senderadcheck:	1
x-ms-exchange-transport-forked:	True
MIME-Version:	1.0
X-MS-Exchange-CrossTenant-mailboxtype:	HOSTED
X-MS-Exchange-CrossTenant-userprincipalname:	GnMXkj+qtsWWLJpi6T8f2Ha+FVeS4fb97/j06Sb3CZREdpbKvhelBmFP1nnkdTV7/KDZISyGnMIrgCAyCwQdJQ==
X-IsSubscribed:	yes
X-MIME-Autoconverted:	from quoted-printable to 8bit by delorie.com id x94ERcsr017812

On 9/29/2019 4:05 PM, Ken Brown wrote:
> On 9/27/2019 10:12 AM, Ken Brown wrote:
>> On 9/27/2019 9:37 AM, Norton Allen wrote:
>>> On 9/26/2019 10:50 PM, Ken Brown wrote:
>>>>
>>>>> As a simple test example, consider:
>>>>>
>>>>> /bin/ssh-agent /bin/sleep 10
>>>>>
>>>>> While the sleep is still running, ps shows:
>>>>>
>>>>>           PID    PPID    PGID     WINPID   TTY         UID    STIME COMMAND
>>>>>          1694    1693    1694       1576  ?          22534 00:01:10
>>>>> /usr/bin/ssh-agent
>>>>>          1653       1    1653      11740  cons1      22534 00:00:37 /usr/bin/bash
>>>>>          1693    1653    1693       1552  cons1      22534 00:01:10 /usr/bin/sleep
>>>>>
>>>>> One oddity is that ssh-agent is listed as a subprocess of sleep
>>>> ...but this isn't a bug.  ssh-agent forks, and then the parent execs the command.
>>>
>>> With the salient difference presumably being that the exec is done in the parent
>>> instead of the child as usual?
>>
>> Yes.  The idea is that 'ssh-agent command' should be more-or-less equivalent to
>> running 'command', with ssh-agent running as a subprocess.
>>
>> The ssh-agent subprocess periodically checks to see if its parent is still
>> alive, and it exits when the parent has died.  Someone should figure out why
>> this is not working on Cygwin.
> 
> As an aid to someone who might want to debug this (probably Corinna when she
> returns), I've created a test program agent.c (attached) that simulates the
> relevant part of ssh-agent:
> 
> 1. It forks a subprocess that periodically checks to see if its parent has died,
> and then exits.
> 
> 2. The parent execs "/usr/bin/sleep 1".
> 
> As with ssh-agent, the subprocess never detects that the parent has died, and so
> it never exits.
> 
> Running this program under strace shows the following error in the pinfo
> constructor:
> 
> pinfo::pinfo: couldn't duplicate parent rd_proc_pipe handle 0x1BC for forked
> child 1666 after exec, Win32 error 5
> 
> [Win32 error 5 is ERROR_ACCESS_DENIED.]

It seems that the pinfo constructor failure happens in 
cygheap_exec_info::reattach_children().  The latter is preceded by the following 
comment:

/* Reattach non-reaped subprocesses passed in from the cygwin process
    which previously operated under this pid.  FIXME: Is there a race here
    if the process exits during cygwin's exec handoff?  */

I tried running my test program under gdb with a breakpoint at 
reattach_children, and the breakpoint was never hit.  That gives an affirmative 
answer to the question in the FIXME.

As a result, the exec'd program never becomes aware that it has a subprocess, so 
it exits without resetting the subprocess's ppid to 1.

Is there someone out there familiar enough with Cygwin's exec to suggest a fix? 
It would be a nice gift to Corinna to get this fixed before her return.

Ken

--
Problem reports:       http://cygwin.com/problems.html
FAQ:                   http://cygwin.com/faq/
Documentation:         http://cygwin.com/docs.html
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple

- Raw text -