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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Sasha Levin <levinsasha928@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org
Subject: Re: [PATCH 3/3] tty_lock: Localise the lock
Date: Mon, 7 May 2012 17:42:40 +0100	[thread overview]
Message-ID: <20120507174240.4209c5cb@pyramind.ukuu.org.uk> (raw)
In-Reply-To: <1336408208.3638.15.camel@lappy>

On Mon, 07 May 2012 18:30:08 +0200
Sasha Levin <levinsasha928@gmail.com> wrote:

> On Mon, 2012-05-07 at 17:11 +0100, Alan Cox wrote:
> > > I don't believe that this change is correct.
> > > 
> > > Consider the following scenario:
> > > 
> > > tty_release -> tty_lock -> pty_close -> tty_vhangup -> tty_lock
> > 
> > We hang up tty->link not tty.
> > 
> > It's now a per tty lock. So I think we are ok.
> 
> Unless we can cause tty->link == tty, in which case:


We should not be able to cause tty->link == tty. So that's a different
problem altogether.

tty->link is set to point to the other half of the pty in pty_install and
in pty98_unix_install. It's never assigned to the same tty and ptys
simply wouldn't work if this wasn't the case.

So whatever your trace is showing, that's not the bug. Something more
complicated would appear to be afoot.

Alan



  reply	other threads:[~2012-05-07 16:39 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-03 21:21 [PATCH 1/3] tty_lock: undo the old tty_lock use on the ctty Alan Cox
2012-05-03 21:22 ` [PATCH 2/3] pty: Lock the devpts bits privately Alan Cox
2012-05-08 18:18   ` H. Peter Anvin
2012-05-08 20:43     ` Alan Cox
2012-05-08 20:41       ` H. Peter Anvin
2012-05-03 21:24 ` [PATCH 3/3] tty_lock: Localise the lock Alan Cox
2012-05-04 20:48   ` Arnd Bergmann
2012-05-04 23:54   ` Greg KH
2012-05-04 23:55     ` Greg KH
2012-05-07 16:03   ` Sasha Levin
2012-05-07 16:03     ` Sasha Levin
2012-05-07 16:11     ` Alan Cox
2012-05-07 16:30       ` Sasha Levin
2012-05-07 16:42         ` Alan Cox [this message]
2012-05-07 17:00           ` Sasha Levin
2012-05-07 21:04             ` Jiri Slaby
2012-05-08 18:12               ` Sasha Levin
2012-05-11 10:40                 ` Sasha Levin
2012-05-11 14:52                   ` Greg KH
2012-05-11 15:09                     ` Sasha Levin
2012-05-11 15:09                       ` Sasha Levin

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