From: Peter Hurley <peter@hurleysoftware.com>
To: David Miller <davem@davemloft.net>
Cc: sasha.levin@oracle.com, samuel@sortiz.org,
gregkh@linuxfoundation.org, jslaby@suse.cz,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ircomm: release tty before sleeping potentially indefintely
Date: Sun, 03 Mar 2013 19:04:25 -0500 [thread overview]
Message-ID: <1362355465.3221.82.camel@thor.lan> (raw)
In-Reply-To: <20130303.174739.1195645942179862011.davem@davemloft.net>
On Sun, 2013-03-03 at 17:47 -0500, David Miller wrote:
> From: Sasha Levin <sasha.levin@oracle.com>
> Date: Sun, 3 Mar 2013 17:35:53 -0500
>
> > ircomm_tty_block_til_ready would hold tty lock while blocking. Since the sleep
> > might take a long time we can prevent other processes from accessing the tty,
> > causing hung tasks and a dead tty.
> >
> > Diagnosed-by: Peter Hurley <peter@hurleysoftware.com>
> > Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
>
> But then you invalidate all of the tty state tests made under
> the lock at the beginning of this function, before enterring
> the loop. If you drop the lock, those pieces of state could
> change.
Yes, the state could change. For example, the tty could be hung up while
ircomm_tty_block_til_ready() is sleeping. Or the session leader could be
exiting and SIGHUPed this task. Or the port could have been shutdown.
All these are re-tested in the loop. What state test isn't repeated?
> I'm not applying this.
That's certainly your perogative.
But you should know this bug hangs the entire tty subsystem.
This is the correct fix and exactly how this is done by the tty port.
Regards,
Peter Hurley
next prev parent reply other threads:[~2013-03-04 0:05 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-03 22:35 [PATCH] ircomm: release tty before sleeping potentially indefintely Sasha Levin
2013-03-03 22:47 ` David Miller
2013-03-03 23:17 ` Sasha Levin
2013-03-04 0:31 ` David Miller
2013-03-04 0:04 ` Peter Hurley [this message]
2013-03-04 0:33 ` David Miller
2013-03-04 1:06 ` Peter Hurley
2013-03-04 2:36 ` David Miller
2013-03-04 4:24 ` Peter Hurley
2013-03-05 16:09 ` [PATCH 0/4] other ircomm_tty fixes (was Re: [PATCH] ircomm: release tty before sleeping potentially indefintely) Peter Hurley
2013-03-05 16:09 ` [PATCH 1/4] net/irda: Fix port open counts Peter Hurley
2013-03-05 16:09 ` [PATCH 2/4] net/irda: Hold port lock while bumping blocked_open Peter Hurley
2013-03-05 16:09 ` [PATCH 3/4] net/irda: Use barrier to set task state Peter Hurley
2013-03-05 16:09 ` [PATCH 4/4] net/irda: Raise dtr in non-blocking open Peter Hurley
2013-03-06 4:44 ` [PATCH 0/4] other ircomm_tty fixes David Miller
2013-03-04 4:30 ` [PATCH] ircomm: release tty before sleeping potentially indefintely Peter Hurley
2013-03-04 2:23 ` Peter Hurley
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