From owner-freebsd-current@FreeBSD.ORG Tue May 13 22:42:12 2014 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id A7467B11 for ; Tue, 13 May 2014 22:42:12 +0000 (UTC) Received: from smtp.rcn.com (smtp.rcn.com [69.168.97.78]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 69BED26CD for ; Tue, 13 May 2014 22:42:11 +0000 (UTC) X_CMAE_Category: , , X-CNFS-Analysis: v=2.0 cv=Nt5TgrhJ c=1 sm=1 a=G/olaBUpLsCobE3dvK+8ZA==:17 a=zOckYCwfLoEA:10 a=ylkbqTKReMEA:10 a=YNqtyO0l_hcA:10 a=LaogzpLLAAAA:8 a=1XWaLZrsAAAA:8 a=6I5d2MoRAAAA:8 a=IHGVAXI7LDoNqkGGsT8A:9 a=wPNLvfGTeEIA:10 a=LGkZmrSRQD0A:10 a=-Z3YCQTyUXzTpWCwZjwA:9 a=_W_S_7VecoQA:10 a=p3HHDZcfAoL1BFB-:21 a=G/olaBUpLsCobE3dvK+8ZA==:117 X-CM-Score: 0 X-Scanned-by: Cloudmark Authority Engine X-Authed-Username: YW5hdEByY24uY29t Authentication-Results: smtp01.rcn.cmh.synacor.com smtp.mail=mi+thun@aldan.algebra.com; spf=neutral; sender-id=neutral Authentication-Results: smtp01.rcn.cmh.synacor.com header.from=mi+thun@aldan.algebra.com; sender-id=neutral Authentication-Results: smtp01.rcn.cmh.synacor.com smtp.user=anat; auth=pass (PLAIN) Received-SPF: neutral (smtp01.rcn.cmh.synacor.com: 209.6.156.90 is neither permitted nor denied by domain of aldan.algebra.com) Received: from [209.6.156.90] ([209.6.156.90:17845] helo=utka.zajac) by smtp.rcn.com (envelope-from ) (ecelerity 3.5.1.37854 r(Momo-dev:3.5.1.0)) with ESMTPA id 0E/E8-56340-DBF92735; Tue, 13 May 2014 18:42:05 -0400 Message-ID: <53729FBC.5060204@aldan.algebra.com> Date: Tue, 13 May 2014 18:42:04 -0400 From: "Mikhail T." User-Agent: Mozilla/5.0 (X11; FreeBSD i386; rv:24.0) Gecko/20100101 Thunderbird/24.0 MIME-Version: 1.0 To: Current FreeBSD Subject: Locking console with Ctrl-S hangs various processes (ttydcd) X-Mailman-Approved-At: Tue, 13 May 2014 23:03:13 +0000 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Content-Filtered-By: Mailman/MimeDel 2.1.18 X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 13 May 2014 22:42:12 -0000 Hello! A fellow FreeBSD user was recently confounded by a problem: various processes on his 10.0 system were hanging or otherwise misbehaving: su, certain daemons, syslogd. They were all hung in the "ttydcd"-state. Searching for that revealed only, that other people have seen the problem, but nobody (including the entire freebsd-stable@ on 2012 ) was able to offer a solution. Apparently, the problem stems from the ttyv0 (which moonlights as /dev/console for the vast majority of installs) being locked -- such as by pressing Ctrl-S. One needs not be a root to do it... After that, any attempts to write to /dev/console -- which even syslog(3) often does -- would hang the calling process until the tty is unlocked (such as with Ctrl-Q). This may be the desired behavior for "normal" ttys, but, perhaps, /dev/console should act differently? -mi