linux-kernel - Re: [PATCH] n_tty_read: check for hanging tty while waiting for input

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Message-ID: <20150217215046.GC13666@redhat.com>
Date:	Tue, 17 Feb 2015 16:50:46 -0500
From:	Aristeu Rozanski <aris@...hat.com>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>
Subject: Re: [PATCH] n_tty_read: check for hanging tty while waiting for input

Hi Peter,
On Tue, Feb 17, 2015 at 04:28:30PM -0500, Peter Hurley wrote:
> On 02/17/2015 04:06 PM, Aristeu Rozanski wrote:
> > If the console has a canonical reader and the respective tty hangs up,
> > it'll waste a wake up and will never release the last ldisc reference so
> > the hangup process can finish:
> 
> This behavior is by-design; /dev/console cannot be hung-up.

hangup is issued on the tty that happens to be the console. In this
case, ttyS0.

> What process is sleeping on /dev/console read() and what is its controlling
> tty? I ask because console teardown usually happens when SIGHUP is
> received by the process group.

ttyS0 is the controller tty.

-- 
Aristeu

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