From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wei Liu <wei.liu2@citrix.com>
Subject: Re: [PATCH] xenconsole: Allow non-interactive use
Date: Thu, 23 Jul 2015 11:53:44 +0100
Message-ID: <20150723105344.GL16933@zion.uk.xensource.com>
References: <1437584888-9074-1-git-send-email-martin@lucina.net>
	<1437641330.19412.37.camel@citrix.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
Received: from mail6.bemta14.messagelabs.com ([193.109.254.103])
	by lists.xen.org with esmtp (Exim 4.72)
	(envelope-from <prvs=6392eb68c=wei.liu2@citrix.com>)
	id 1ZIE8L-0002e9-SI
	for xen-devel@lists.xenproject.org; Thu, 23 Jul 2015 10:53:49 +0000
Content-Disposition: inline
In-Reply-To: <1437641330.19412.37.camel@citrix.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Ian Campbell <ian.campbell@citrix.com>
Cc: xen-devel@lists.xenproject.org, Martin Lucina <martin@lucina.net>, Wei Liu <wei.liu2@citrix.com>, Ian Jackson <ian.jackson@eu.citrix.com>, Stefano Stabellini <stefano.stabellini@eu.citrix.com>
List-Id: xen-devel@lists.xenproject.org

On Thu, Jul 23, 2015 at 09:48:50AM +0100, Ian Campbell wrote:
> On Wed, 2015-07-22 at 19:08 +0200, Martin Lucina wrote:
> > If xenconsole is run with stdin closed or redirected to /dev/null,
> > console_loop() will return immediately due to failure to read from
> > STDIN_FILENO. This patch tests if stdin and stdout are both connected 
> > to
> > a TTY and, if not, xenconsole will not attempt to read from stdin or
> > modify stdout terminal attributes.
> > 
> > Existing behaviour when xenconsole is run from a terminal does not
> > change.
> > 
> > This allows for non-interactive use, eg. running "xl create -c" under
> > systemd or piping the output of "xl console" to another command.
> > 
> > Signed-off-by: Martin Lucina <martin@lucina.net>
> > Cc: Ian Jackson <ian.jackson@eu.citrix.com>
> > Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> > Cc: Ian Campbell <ian.campbell@citrix.com>
> > Cc: Wei Liu <wei.liu2@citrix.com>
> 
> Acked-by: Ian Campbell <ian.campbell@citrix.com>
> 
> WRT the 4.6 freeze I'm torn between calling this a feature or a bugfix.
> 

I'm inclined to say it's a bugfix. It is reasonable that users want to
pipe console output to logging daemon.

Wei.

> A pair of nits, which probably aren't worth acting on:
> 
> > @@ -176,8 +177,13 @@ static int console_loop(int fd, struct xs_handle
> > *xs, char *pty_path)
> >  		fd_set fds;
> >  
> >  		FD_ZERO(&fds);
> > -		FD_SET(STDIN_FILENO, &fds);
> > -		max_fd = STDIN_FILENO;
> > +		if (interactive) {
> > +			FD_SET(STDIN_FILENO, &fds);
> > +			max_fd = STDIN_FILENO;
> > +		}
> > +		else {
> > +			max_fd = -1;
> > +		}
> 
> Looking at the rest of the file and tools/console subtree it seems the
> prevailing coding style is:
> 
> 		} else
>                 	                max_fd = -1;
> 
> (i.e. } brace on the same line as the else and no {} for single
> statements after an else).
> 
> But maybe it would be better to set max_fd = -1 on declaration and do
> the max dance here as with the following cases?
> 
> Ian.