linux-kernel - Re: VFS deadlock ?

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Message-ID: <CA+55aFxSehUm6CSR=2edeK4STXhV6OWmZrmrGhLOsORXq-D8sw@mail.gmail.com>
Date:	Thu, 21 Mar 2013 17:19:53 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: VFS deadlock ?

Thinking some more..

On Thu, Mar 21, 2013 at 5:15 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> Hmm. But again, that can't actually happen here. We're in /proc. You
> can't move the entries around.

.. this wasn't a good argument, because we will take the locks before
we do that.

> Also, we only changed the locking order
> for the "inode is identical" case where we take only *one* lock, we
> didn't change it for the cases where we take multiple locks (and order
> them topologically).

.. and this isn't a good argument either, because your argument was
that you can get the deadlock by always taking two directories, and
never hitting the alias case itself.

Hmm.

             Linus
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