X-Recipient: archive-cygwin AT delorie DOT com
DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 007F8385E440
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1585761268;
	bh=Uhs0wN/tv1UFbCX5nV2+t+ut5MG7+hi4znC7EY9GWe4=;
	h=To:References:In-Reply-To:Subject:Date:List-Id:List-Unsubscribe:
	 List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:Cc:
	 From;
	b=m5J1fxgIxcg9YCxIBa2Uoz/n/DLvkYGIuwwKibyISRYhc+m8UCGOjsING7BSNRdUg
	 zlVhercjQ/wQxDQDbU3lAytJ8MSvRiFv890o0zJBBm5J+EX6i7z0Qqe2pupqiNPug2
	 RSVzMwPSaU2yg9X53mxaqAEEU60wy8ooH01hUqLU=
X-Original-To: cygwin AT cygwin DOT com
Delivered-To: cygwin AT cygwin DOT com
DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 741E4385E02F
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
 d=1e100.net; s=20161025;
 h=x-gm-message-state:from:to:cc:references:in-reply-to:subject:date
 :message-id:mime-version:content-transfer-encoding:content-language
 :thread-index;
 bh=hInPBMjjGEYV+8/HOgljBT/jkW1gs54cdUxmpmAJ5WE=;
 b=cCxMXp5yodM0un4UsoNaM6gIyn5UtmFltP2YFSVHwPAQB42pnb/NLyl4PDUWJnvH/3
 AU1Xwr5vRd0ZOcJ3M6en83I2Y3hwU3oemtH4sYA6CMH/TP0/jfzpUJcM7cmqNUnqi5bL
 sZ2q7Z65xCqA73pkIlnIvkGd+kyEaUnRCiCQ+B+R04Fa961GaTX8lOre7sUAKlb6oLSu
 IDJKkm2YweGHyj6LY3Tqvy7WhIr4OUwz+CBzFnwiMousdYgDhQkPTvOAO48IG6FWeqeT
 tkge0C8/cfb9T4z0JG4vqUNx0tgeUvbM5H8RhVmpS7ge0OoOkoiv1tcPWH4FSBALHtho
 zqrg==
X-Gm-Message-State: AGi0PuZeMD3TyeHkyLvLEHrI6df4xR3dC/a3Sn0PUvhbVl4Hsv5ifngM
 OVgUwmrQwAyNtKwJhJ1yKwf48G/K
X-Google-Smtp-Source: APiQypLjwkc+ZC5hyS5P7HDjMY7771N3aKvCKhWD4W11y8YmRRv+e0A2OUm6q4+ZBCY8E7Ubxz64hw==
X-Received: by 2002:a19:4ad4:: with SMTP id x203mr15338658lfa.64.1585761263755; 
 Wed, 01 Apr 2020 10:14:23 -0700 (PDT)
To: "'Ken Brown'" <kbrown AT cornell DOT edu>
References: <1b1401d60296$2769e690$763db3b0$@gmail.com>
 <716e2076-f607-454e-2723-937c3959e2a3 AT cornell DOT edu>
 <18be01d602ab$0bbfca30$233f5e90$@gmail.com>
 <35b43b59-6410-f21f-710c-385e39cbae0b AT cornell DOT edu>
 <005201d603ba$2bc8ab20$835a0160$@gmail.com>
 <472d1df6-531a-ebd7-4ffa-583a06e270ff AT cornell DOT edu>
 <ce4a4877-df77-3400-e8ac-16655b313757 AT cornell DOT edu>
 <b311d907-7376-5bc6-3216-7d2b96728dbc AT cornell DOT edu>
 <00b901d60447$7ecb4c50$7c61e4f0$@gmail.com>
 <f8f5c9b4-9eb9-85b0-ab8f-44b3b2458e0b AT cornell DOT edu>
 <00e001d604f9$d0aa0720$71fe1560$@gmail.com>
 <8c6c5655-c162-8361-9f44-376bbd7cf114 AT cornell DOT edu>
 <d213c473-00c2-0308-b720-d8f274126681 AT cornell DOT edu>
 <3fe06192-7300-382a-8c98-f1bc2ff81e36 AT cornell DOT edu>
 <003701d607a0$c975f140$5c61d3c0$@gmail.com>
 <249be61e-da8a-7da1-ca67-0c4c6433a415 AT cornell DOT edu>
 <000a01d60802$d1525900$73f70b00$@gmail.com>
 <f7922d62-097c-e284-ded5-6d7a1c0f0d66 AT cornell DOT edu>
In-Reply-To: <f7922d62-097c-e284-ded5-6d7a1c0f0d66@cornell.edu>
Subject: Sv: Sv: Sv: Sv: Sv: Sv: Sv: Named pipes and multiple writers
Date: Wed, 1 Apr 2020 19:14:21 +0200
Message-ID: <001601d60848$fcffd320$f6ff7960$@gmail.com>
MIME-Version: 1.0
X-Mailer: Microsoft Outlook 16.0
Content-Language: en-gb
Thread-Index: AQJE9fQg8TMZuJRGwTEKbo0ZGNgDeQHtMggPA01jw/MCH/KUAAKPevBvAf/qW+kC4eksHQHeBGSzAqmcYp4CB8F8lwIBR+2oARkkbuUCauCM3AJYP32sAmYz8EcC5hrYQwEcxqeZAcg8ToumW1EdAA==
X-Spam-Status: No, score=-2.4 required=5.0 tests=BAYES_00, DKIM_SIGNED,
 DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, RCVD_IN_DNSWL_NONE,
 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-Archive: <http://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: <http://cygwin.com/mailman/listinfo/cygwin>,
 <mailto:cygwin-request AT cygwin DOT com?subject=subscribe>
From: Kristian Ivarsson via Cygwin <cygwin AT cygwin DOT com>
Reply-To: sten DOT kristian DOT ivarsson AT gmail DOT com
Cc: "'cygwin'" <cygwin AT cygwin DOT com>
Content-Type: text/plain; charset="iso-8859-1"
Sender: "Cygwin" <cygwin-bounces AT cygwin DOT com>
Content-Transfer-Encoding: 8bit
X-MIME-Autoconverted: from quoted-printable to 8bit by delorie.com id 031HEqfw009668

> On 4/1/2020 4:52 AM, sten DOT kristian DOT ivarsson AT gmail DOT com wrote:
> >> On 3/31/2020 5:10 PM, sten DOT kristian DOT ivarsson AT gmail DOT com wrote:
> >>>> On 3/28/2020 10:19 PM, Ken Brown via Cygwin wrote:
> >>>>> On 3/28/2020 11:43 AM, Ken Brown via Cygwin wrote:
> >>>>>> On 3/28/2020 8:10 AM, sten DOT kristian DOT ivarsson AT gmail DOT com wrote:
> >>>>>>>> On 3/27/2020 10:53 AM, sten DOT kristian DOT ivarsson AT gmail DOT com wrote:
> >>>>>>>>>> On 3/26/2020 7:19 PM, Ken Brown via Cygwin wrote:
> >>>>>>>>>>> On 3/26/2020 6:39 PM, Ken Brown via Cygwin wrote:
> >>>>>>>>>>>> On 3/26/2020 6:01 PM, sten DOT kristian DOT ivarsson AT gmail DOT com wrote:
> >>>>>>>>>>>>> The ENIXIO occurs when parallel child-processes
> >>>>>>>>>>>>> simultaneously using O_NONBLOCK opening the descriptor.
> >>>>>>>>>>>>
> >>>>>>>>>>>> This is consistent with my guess that the error is
> >>>>>>>>>>>> generated by fhandler_fifo::wait.  I have a feeling that
> >>>>>>>>>>>> read_ready should have been created as a manual-reset
> >>>>>>>>>>>> event, and that more care is needed to make sure it's set
when it should be.

[snip] 

> >>>>> Never mind.  I was able to reproduce the problem and find the cause.
> >>>>> What happens is that when the first subprocess exits,
> >>>>> fhandler_fifo::close resets read_ready.  That causes the second
> >>>>> and subsequent subprocesses to think that there's no reader open,
> >>>>> so their attempts to open a writer with O_NONBLOCK fail with ENXIO.

[snip] 

> > I wrote in a previous mail in this topic that it seemed to work fine
> > for me as well, but when I bumped up the numbers of writers and/or the
> > number of messages (e.g. 25/25) it starts to fail again

[snip] 

> Yes, it is a resource issue.  There is a limit on the number of writers
that can be open at one
> time, currently 64.  I chose that number arbitrarily, with no idea what
might actually be
> needed in practice, and it can easily be changed.

Does it have to be a limit at all ? We would rather see that the application
decide how much resources it would like to use. In our particular case there
will be a process-manager with an incoming pipe that possible several
thousands of processes will write to

Just for fiddling around (to figure out if this is the limit that make other
things work a bit odd), where's this 64 limit defined now ?

> In addition, a writer isn't recognized as closed until a reader tries to
read and gets an error.
> In your example with 25/25, the list of writers quickly gets to 64 before
the parent ever tries
> to read.

That explains the behaviour, but should there be some error returned from
open/write (maybe it is but I'm missing it) ?

> I'll see if I can find a better way to manage this.
> 
> Ken

Kristian
Kristian 

--
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