linux-kernel - Re: Why are not processes HUPped when they open /dev/console?

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Message-ID: <20120206192406.GB28687@atrey.karlin.mff.cuni.cz>
Date:	Mon, 6 Feb 2012 20:24:07 +0100
From:	Pavel Machek <pavel@....cz>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg KH <greg@...ah.com>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: Why are not processes HUPped when they open /dev/console?

> On 01/25/2012 10:45 PM, Alan Cox wrote:
> > On Wed, 25 Jan 2012 22:38:40 +0100
> > Jiri Slaby <jslaby@...e.cz> wrote:
> > 
> >> Hello,
> >>
> >> don't you remember by a chance the reason for this test in __tty_hangup:
> >>   if (filp->f_op->write != tty_write)
> >>
> >> The logic there is not to HUP processes that have this tty open via
> >> /dev/console.
> > 
> > Because if you hang up the console the machine crashes ?
> >
> > At least that's what used to happen.
> 
> It does not crash anymore. However the system (systemd more precisely)
> is confused a bit (well, a huge). So I suppose the test has its meaning.
> 
> The whole exercise was about how to fix the userspace issue introduced
> by the added infinite timeout.

> I think the proper solution here is just not to call vhangup in
> userspace for the device which is /dev/console. It never worked anyway.
> Because the HUP signal was never sent and it always timed out.

Perhaps the "infinite timeout" should be reverted, then? It sounds
like a regression...



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