X-Recipient:	archive-cygwin AT delorie DOT com
X-Original-To:	cygwin AT cygwin DOT com
Delivered-To:	cygwin AT cygwin DOT com
DMARC-Filter:	OpenDMARC Filter v1.3.2 sourceware.org 43C573857815
Authentication-Results:	sourceware.org; dmarc=none (p=none dis=none)
	header.from=huarp.harvard.edu
Authentication-Results:	sourceware.org;
	spf=pass smtp.mailfrom=allen AT huarp DOT harvard DOT edu
Subject:	Re: Unix Domain Socket Limitation?
From:	Norton Allen <allen AT huarp DOT harvard DOT edu>
To:	Ken Brown <kbrown AT cornell DOT edu>, cygwin <cygwin AT cygwin DOT com>
References:	<71490665-31b0-f63c-74da-461a053fac21 AT huarp DOT harvard DOT edu>
	<55ea1649-1979-6238-75ab-69100c22e069 AT cornell DOT edu>
	<4260ad1b-4ab2-fa36-fd0e-7c9644560114 AT huarp DOT harvard DOT edu>
	<38a82f82-1ef9-768e-7d3e-15f63147e188 AT cornell DOT edu>
	<a1f6e9af-7c0b-4d3f-4198-1c7bff4869dc AT huarp DOT harvard DOT edu>
	<16165727-f614-1543-70bc-36457ddbf260 AT cornell DOT edu>
	<75d1315b-5a56-a2e5-310d-6ac33a3cf17c AT huarp DOT harvard DOT edu>
	<f5373cd4-1d3e-500a-a967-1c558541e720 AT cornell DOT edu>
	<85c9c70f-c016-0f88-099e-5c772adbc648 AT huarp DOT harvard DOT edu>
Message-ID:	<fb523694-7775-1d7a-db55-27ccbd6d157c@huarp.harvard.edu>
Date:	Mon, 30 Nov 2020 21:22:56 -0500
User-Agent:	Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101
	Thunderbird/78.5.0
MIME-Version:	1.0
In-Reply-To:	<85c9c70f-c016-0f88-099e-5c772adbc648@huarp.harvard.edu>
X-Spam-Status:	No, score=-3.5 required=5.0 tests=BAYES_00, KAM_DMARC_STATUS,
	NICE_REPLY_A, RCVD_IN_DNSWL_LOW, SPF_HELO_NONE, SPF_PASS,
	TXREP autolearn=ham autolearn_force=no version=3.4.2
X-Spam-Checker-Version:	SpamAssassin 3.4.2 (2018-09-13) on
	server2.sourceware.org
X-BeenThere:	cygwin AT cygwin DOT com
X-Mailman-Version:	2.1.29
List-Id:	General Cygwin discussions and problem reports <cygwin.cygwin.com>
List-Unsubscribe:	<https://cygwin.com/mailman/options/cygwin>,
	<mailto:cygwin-request AT cygwin DOT com?subject=unsubscribe>
List-Archive:	<https://cygwin.com/pipermail/cygwin/>
List-Post:	<mailto:cygwin AT cygwin DOT com>
List-Help:	<mailto:cygwin-request AT cygwin DOT com?subject=help>
List-Subscribe:	<https://cygwin.com/mailman/listinfo/cygwin>,
	<mailto:cygwin-request AT cygwin DOT com?subject=subscribe>
Errors-To:	cygwin-bounces AT cygwin DOT com
Sender:	"Cygwin" <cygwin-bounces AT cygwin DOT com>
X-MIME-Autoconverted:	from quoted-printable to 8bit by delorie.com id 0B12faIQ001081

On 11/30/2020 9:14 PM, Norton Allen wrote:
> On 11/30/2020 6:19 PM, Ken Brown wrote:
>> On 11/30/2020 1:26 PM, Norton Allen wrote:
>>> On 11/30/2020 1:14 PM, Ken Brown wrote:
>>>> I can reproduce the hang, and it happens if I use the new AF_UNIX 
>>>> code also. But what I'm seeing (at least with the new code) isn't 
>>>> exactly what you describe.
>>>>
>>>> When the server's first select call returns, accept succeeds. The 
>>>> server then calls select a second time, and that call doesn't 
>>>> return. I haven't checked yet to see what's going on in the client, 
>>>> and I may not get to that for a while.
>>>>
>>> That's good news, and seems to be consistent with my theory that it 
>>> is some sort of race condition that might be particularly sensitive 
>>> to system-specific timing. I am compiling cygwin1.dll now.
>>
>> Hi Norton,
>>
>> I think there's a mistake in your test program.  Shouldn't 
>> client_pselect() be waiting for the socket to be write-ready rather 
>> than read-ready?  Here's a quote from the Posix page for 'connect':
>>
>> If the connection cannot be established immediately and O_NONBLOCK is 
>> set for the file descriptor for the socket, connect() shall fail and 
>> set errno to [EINPROGRESS], but the connection request shall not be 
>> aborted, and the connection shall be established asynchronously....
>>
>> When the connection has been established asynchronously, pselect(), 
>> select(), and poll() shall indicate that the file descriptor for the 
>> socket is ready for writing.
>>
> Yes, you are correct. In fact I had already fixed that bug on another 
> branch, then forgot to update it on this one. I also noticed another 
> bug in calculating width. Now I am not getting the blocking behavior 
> but instead getting the wrong bits set in select(). I think I'd better 
> pick this up in the morning when I am thinking straight!

Yeah, so now the example no longer blocks for me. Unfortunately these 
bugs are not present in my application, so I will need to keep working 
on this.


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

- Raw text -