From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Michael Breuer <mbreuer@majjas.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: tty_io.c - disassociate_ctty attempted to write to tty = NULL question/problem?
Date: Tue, 5 Jan 2010 00:12:05 +0000 [thread overview]
Message-ID: <20100105001205.7e8f131b@lxorguk.ukuu.org.uk> (raw)
In-Reply-To: <4B42733D.6050704@majjas.com>
> do_exit -> disassocate_ctty(1) (for tty1).
> disassociate->vhangup->do_tty_hangup
>
> In do_tty_hangup, p->signal->tty is set to NULL, where p==current.
Perfectly reasonable so far - the current process gave up having a
controlling tty.
> On return, the aforementioned error message is generated.
>From where - the backtrace on the write to NULL tty is the important bit
here. User space interfaces cache tty in filp->private_data so its not
going to be coming from there unless there was a memory scribble which
would imply a refcounting bug - and I'd expect people to hit that
reliably.
Some kernel stuff does take a peek at p->signal->tty for direct printk
type stuff and that sounds more likely - the backtraceon the write to
NULL tty is going to provide the needed info.
Alan
next prev parent reply other threads:[~2010-01-05 0:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-01-04 23:01 Michael Breuer
2010-01-05 0:12 ` Alan Cox [this message]
2010-01-05 5:48 ` Michael Breuer
2010-01-05 10:47 ` Alan Cox
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