Date: Tue, 13 May 2014 18:42:04 -0400 From: "Mikhail T." <mi+thun@aldan.algebra.com> To: Current FreeBSD <freebsd-current@freebsd.org> Subject: Locking console with Ctrl-S hangs various processes (ttydcd) Message-ID: <53729FBC.5060204@aldan.algebra.com>
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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 <https://www.google.com/search?q=FreeBSD+ttydcd>; for that revealed only, that other people have seen the problem, but nobody (including the entire freebsd-stable@ on 2012 <http://lists.freebsd.org/pipermail/freebsd-stable/2012-June/068281.html>) 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
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