From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from endymion.arp.harvard.edu (endymion.arp.harvard.edu [140.247.179.94]) by sourceware.org (Postfix) with ESMTPS id 6D9BE385481D for ; Tue, 1 Dec 2020 02:14:52 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 6D9BE385481D Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=huarp.harvard.edu Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=allen@huarp.harvard.edu Received: from [192.168.7.23] (pool-74-104-152-231.bstnma.fios.verizon.net [74.104.152.231]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by endymion.arp.harvard.edu (Postfix) with ESMTPSA id BCD2B6C095A; Mon, 30 Nov 2020 21:14:51 -0500 (EST) Subject: Re: Unix Domain Socket Limitation? To: Ken Brown , cygwin References: <71490665-31b0-f63c-74da-461a053fac21@huarp.harvard.edu> <55ea1649-1979-6238-75ab-69100c22e069@cornell.edu> <4260ad1b-4ab2-fa36-fd0e-7c9644560114@huarp.harvard.edu> <38a82f82-1ef9-768e-7d3e-15f63147e188@cornell.edu> <16165727-f614-1543-70bc-36457ddbf260@cornell.edu> <75d1315b-5a56-a2e5-310d-6ac33a3cf17c@huarp.harvard.edu> From: Norton Allen Message-ID: <85c9c70f-c016-0f88-099e-5c772adbc648@huarp.harvard.edu> Date: Mon, 30 Nov 2020 21:14:58 -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: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US 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@cygwin.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: General Cygwin discussions and problem reports List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 01 Dec 2020 02:14:53 -0000 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!