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

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Message-ID: <4F207660.500@suse.cz>
Date:	Wed, 25 Jan 2012 22:38:40 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Greg KH <greg@...ah.com>, LKML <linux-kernel@...r.kernel.org>
Subject: Why are not processes HUPped when they open /dev/console?

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.

It is there like forever. But now, due to that, processes that do
vhangup of /dev/ttyXYZ wait infinitely if there is some other process
that has the ttyXYZ open through /dev/console. (Due to infinite wait in
tty_ldisc_hangup.)

This happens on some distros on shutdown path because they do vhangup on
all tty[0-8] ttyS[01] and similar.

thanks,
-- 
js
suse labs
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