DKIM-Filter:	OpenDKIM Filter v2.11.0 delorie.com 46PG3eVS4080302
Authentication-Results:	delorie.com;
	dkim=pass (1024-bit key, unprotected) header.d=cygwin.com header.i=@cygwin.com header.a=rsa-sha256 header.s=default header.b=ndRpFWPa
X-Recipient:	archive-cygwin AT delorie DOT com
DKIM-Filter:	OpenDKIM Filter v2.11.0 sourceware.org 9FF7F3858430
DKIM-Signature:	v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1721923418;
	bh=fBFZxUaK0Ugls6wuI0FuRv0IAv4Hre4/L4e+PrRAfj8=;
	h=Date:Subject:To:List-Id:List-Unsubscribe:List-Archive:List-Post:
	List-Help:List-Subscribe:From:Reply-To:From;
	b=ndRpFWPaYf9RVI7YiWzWX52Xw5I0Yts6CUQ34k78cTbZmH9DoBfswT6XwAXiV/AbB
	k/bAkQS8TQE6eDQQyD/vEnSTV3k9whvddb715yAh93WTd0yB8x3KVz9t1GiK5X+g4l
	ARmU6cSa7bo3MJ7yX+KgRSMNsmIh0A0I4LYel4T0=
X-Original-To:	cygwin AT cygwin DOT com
Delivered-To:	cygwin AT cygwin DOT com
DMARC-Filter:	OpenDMARC Filter v1.4.2 sourceware.org 765F73858D35
ARC-Filter:	OpenARC Filter v1.0.0 sourceware.org 765F73858D35
ARC-Seal:	i=1; a=rsa-sha256; d=sourceware.org; s=key; t=1721923361; cv=none;
	b=jh8Gk3kz/ia1VodKMSjaOEz+RZ+spxFa1HlXfxNTf0rAvDmVRnEnCBviBJ8Jk1GxXvNbaH2RSRlpsyttDhrM/kiFpr84S1UPArDaXmfqqFTcu12Oh6renG39AA8uz+65h1CFJYQLvTbw1Y9GEhrpaZ08aguXKpZCpA148NcvVBs=
ARC-Message-Signature:	i=1; a=rsa-sha256; d=sourceware.org; s=key;
	t=1721923361; c=relaxed/simple;
	bh=oJP4IYw4rRs/B0VtxW/T9vUrp+epnlpp1+L+kwdMSZ8=;
	h=DKIM-Signature:MIME-Version:From:Date:Message-ID:Subject:To;
	b=pNhjlvQLDdBk7gn5PZKl+67AWusSNbYiIrvDErI1p9foUNMyXSkSBb5PiJEWI0v5bOFhQOwcM6sIy1O8FEk0HdD5mTOi4tFoWs3C1GEV2DUJWFCsXtyI4jFXBBh0iJQ6oJxZ7DK/dyqDxQVw/SvGm8lPEautDwGcJ+wT7fnMQ3A=
ARC-Authentication-Results:	i=1; server2.sourceware.org
X-Google-DKIM-Signature:	v=1; a=rsa-sha256; c=relaxed/relaxed;
	d=1e100.net; s=20230601; t=1721923358; x=1722528158;
	h=to:subject:message-id:date:from:mime-version:x-gm-message-state
	:from:to:cc:subject:date:message-id:reply-to;
	bh=oJP4IYw4rRs/B0VtxW/T9vUrp+epnlpp1+L+kwdMSZ8=;
	b=PXQFRKKSX7KHZfnaN5wvMSBtM6i8LCo6nqxLLJ4VzcokWXecdZqjKUzNLisRDodhRi
	u2d4dj+SHM+9fu44bUVpa3R0V5cZw9ik8MDOIkQxyez39VNp0Lfd/kkgyHFeDHLELB0z
	YGj6FNdz9WcRGiFUscPhGk30Hh75BSuNlubMUzm9nWt8gfU4KszGpBmwUVYMxMrBRpwT
	/bsBxBQYiO9hQPNU/OeUNRiyQf23OvNdo58pvODk7Mla8ThdZaH9iQ0SDTafcaxZ1HSI
	AjObN3god3yiCBGxLqYGiQjHRvXtcZ+pKp398iZ1ru9FWPTtDEYncunk24U+s7cdgarB
	kvkQ==
X-Gm-Message-State:	AOJu0Yyjz5TmH9O0I8MNlwh3gpmudXUoy0EqyGFWXfA3WqAz/et+1vSC
	xg5ROjLLyU1batgWyAIL1OwC/wyyy1lNGTs3xHnSA5B9U7Qwqdxro6REjjXq+Z/oZ/KAO6uTzuU
	PZZp8Yfw0EPE2yYOhgwHo8pWqCgT3MHBI
X-Google-Smtp-Source:	AGHT+IE0TNe8HsxJ/noPVsSc5Fm+ExWtZmWifo+wgp+kAge/3HP4m83UDw670Uo6EX5r9Sr2kXVL6rvkDG8aRDdTAPY=
X-Received:	by 2002:a17:90b:3844:b0:2c9:a3d4:f044 with SMTP id
	98e67ed59e1d1-2cf237b7546mr3343493a91.11.1721923357954; Thu, 25 Jul 2024
	09:02:37 -0700 (PDT)
MIME-Version:	1.0
Date:	Thu, 25 Jul 2024 12:02:21 -0400
Message-ID:	<CADnnjUU5Q=C6S_8F9Akp3J5-t89O3i7xLoEsWqgXNRBPBkkdcw@mail.gmail.com>
Subject:	RE: Rewriting the FIFO code
To:	cygwin AT cygwin DOT com
X-Spam-Status:	No, score=-2.1 required=5.0 tests=BAYES_00, DKIM_SIGNED,
	DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, HTML_MESSAGE,
	RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS,
	TXREP autolearn=ham autolearn_force=no version=3.4.6
X-Spam-Checker-Version:	SpamAssassin 3.4.6 (2021-04-09) on
	server2.sourceware.org
X-Content-Filtered-By:	Mailman/MimeDel 2.1.30
X-BeenThere:	cygwin AT cygwin DOT com
X-Mailman-Version:	2.1.30
List-Id:	General Cygwin discussions and problem reports <cygwin.cygwin.com>
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>
From:	Jameson Nash via Cygwin <cygwin AT cygwin DOT com>
Reply-To:	Jameson Nash <vtjnash AT gmail DOT com>
Sender:	"Cygwin" <cygwin-bounces~archive-cygwin=delorie DOT com AT cygwin DOT com>

I am hopping in late to this conversation, after working on debugging a
confusing issue where my NamedPipe stopped working reliably after being
passed to a cygwin program, where I believe it used to work okay with older
versions of cygwin. I just want to point out that the current flag being
used (Win32 calls it PIPE_NOWAIT) is documented as do-not-use (e.g.
https://devblogs.microsoft.com/oldnewthing/20110114-00/?p=11753) as it
interferes with the reliable execution of other programs that are using the
same pipe end, and that do not want to use the inefficient busy-wait
polling that cygwin's implementation does. As the documentation points out,
there is no way to recover correct behavior of OVERLAPPED while the flag is
enabled. By contrast, however, with PIPE_WAIT mode, it is possible to
implement non-blocking IO, including select, with OVERLAPPED operations, by
using ReadFile (with a size of 0) followed by PeekNamedPipe (if you want to
estimate the number of bytes to read) followed by a ReadFile of that number
of bytes (or an estimated number) followed by an immediate CancelIOEx (or
CancelIO on older platforms). I can post some example code from libuv if
that would be helpful? Removing this `PIPE_WAIT` change would eventually
also allow fixing the implementation of `select` in cygwin to actually use
event-driven notifications instead of emulating them with a slow loop as is
done now (https://cygwin.com/cygwin-ug-net/highlights.html).

Thanks!

-jameson

post note: I also wrote up some of this in
https://github.com/libuv/libuv/issues/4467 so that google hopefully indexes
it in case anyone manages to run across the same problem in nodejs and
searches for related issues, but I only wrote a few details there of how
libuv might be impacted by this, without the specifics of how cygwin could
be fixed

-- 
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 -