X-Recipient:	archive-cygwin AT delorie DOT com
DKIM-Filter:	OpenDKIM Filter v2.11.0 sourceware.org 0B2BF3858413
DKIM-Signature:	v=1; a=rsa-sha256; c=relaxed/relaxed; d=cygwin.com;
	s=default; t=1692953369;
	bh=w9829CS4P2JwSqlUpPYOZFDCn7BQPRkps83IKzbMuME=;
	h=Date:To:Subject:In-Reply-To:References:List-Id:List-Unsubscribe:
	List-Archive:List-Post:List-Help:List-Subscribe:From:Reply-To:
	From;
	b=LxLAe0UGFlK9KXa2WgKriOBP8H3Q5xsAUFzokvDym55Uq9vsI64G1oEAHXNWA0HYJ
	l3NSPGvR2L3azsa6kKS8rJi11B5m4bYMEhr+om4q7RItud/t9tguV5pUq4tB8kpwaN
	N948t9jOyyhABpXKADwCeZ4sjFSyDJclovuzeErc=
X-Original-To:	cygwin AT cygwin DOT com
Delivered-To:	cygwin AT cygwin DOT com
DMARC-Filter:	OpenDMARC Filter v1.4.2 sourceware.org 2AB163858C53
Date:	Fri, 25 Aug 2023 17:48:32 +0900
To:	cygwin AT cygwin DOT com
Subject:	Re: scp stalls on uploading in cygwin 3.5 current master.
Message-Id:	<20230825174832.9ebae8112667d5d5411cb8db@nifty.ne.jp>
In-Reply-To:	<ZOcb9SKtMPTQfj/m@calimero.vinschen.de>
References:	<20230824060502 DOT c4798062cb19d4d35a5633ae AT nifty DOT ne DOT jp>
	<20230824123131 DOT 390b4471915c963425c77608 AT nifty DOT ne DOT jp>
	<ZOcb9SKtMPTQfj/m AT calimero DOT vinschen DOT de>
X-Mailer:	Sylpheed 3.7.0 (GTK+ 2.24.30; i686-pc-mingw32)
Mime-Version:	1.0
X-Spam-Status:	No, score=-11.3 required=5.0 tests=BAYES_00, GIT_PATCH_0,
	KAM_DMARC_STATUS, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_PASS, 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-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>
From:	Takashi Yano via Cygwin <cygwin AT cygwin DOT com>
Reply-To:	Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>
Errors-To:	cygwin-bounces+archive-cygwin=delorie DOT com AT cygwin DOT com
Sender:	"Cygwin" <cygwin-bounces+archive-cygwin=delorie DOT com AT cygwin DOT com>

On Thu, 24 Aug 2023 10:59:33 +0200
Corinna Vinschen wrote:
> > I'm not sure why at all, however, the following patch seems to
> > solve the issue.
> > 
> > diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc
> > index 7b9473849..de5794c9f 100644
> > --- a/winsup/cygwin/select.cc
> > +++ b/winsup/cygwin/select.cc
> > @@ -1790,7 +1790,7 @@ peek_socket (select_record *me, bool)
> >        if (events & FD_WRITE)
> >  	{
> >  	  wfd_set w = { 1, { fh->get_socket () } };
> > -	  TIMEVAL t = { 0 };
> > +	  TIMEVAL t = { .tv_sec = 0, .tv_usec = 1 };
> >  
> >  	  if (_win32_select (0, NULL, &w, NULL, &t) == 0)
> >  	    events &= ~FD_WRITE;
> 
> Yeah, this is weird. A TIMEVAL value of 0 indicates non-blocking,
> so why should waiting a usec make that better?  It also potentially
> slows down Cygwin's select noticably if multiple sockets are part
> of the descriptor set.
> 
> Hmmm.
> 
> Is it possible that _win32_select returns with SOCKET_ERROR for 
> some reason?
> 
> Unfortunately I'm a bit swamped ATM, but rather than setting t to 1
> usec, what if the check goes:
> 
>   if (_win32_select (0, NULL, &w, NULL, &t) != 1)
> 
> ?

This did not help. I looked into this deeper and noticed that:
1) _win32_select() sometimes returns 0.
2) If _win32_select() returns 0, WaitForMultipleObjects(..., INFINITE)
   is called in thread_socket().
3) WaitForMultipleObjects() sometimes does not return for FD_WRITE
   for unknown reason.
This causes the stall.

-- 
Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>

-- 
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 -