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

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Date:	Thu, 26 Jan 2012 14:15:41 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	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.

thanks,
-- 
js
suse labs
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