netdev - Re: possible circular locking dependency detected

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Date:   Fri, 2 Sep 2016 10:43:20 -0400 (EDT)
From:   CAI Qian <caiqian@...hat.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Al Viro <viro@...iv.linux.org.uk>,
        Miklos Szeredi <miklos@...redi.hu>,
        Rainer Weikusat <rweikusat@...eradapt.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Rainer Weikusat <rweikusat@...ileactivedefense.com>,
        Eric Sandeen <esandeen@...hat.com>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: possible circular locking dependency detected



----- Original Message -----
> From: "Linus Torvalds" <torvalds@...ux-foundation.org>
> To: "Al Viro" <viro@...iv.linux.org.uk>, "CAI Qian" <caiqian@...hat.com>
> Cc: "Miklos Szeredi" <miklos@...redi.hu>, "Rainer Weikusat" <rweikusat@...eradapt.com>, "Hannes Frederic Sowa"
> <hannes@...essinduktion.org>, "Rainer Weikusat" <rweikusat@...ileactivedefense.com>, "Eric Sandeen"
> <esandeen@...hat.com>, "Network Development" <netdev@...r.kernel.org>
> Sent: Thursday, September 1, 2016 6:04:38 PM
> Subject: Re: possible circular locking dependency detected
> 
> On Thu, Sep 1, 2016 at 2:43 PM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
> > On Thu, Sep 1, 2016 at 2:01 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> >>
> >> Outside as in "all fs activity in bind happens under it".  Along with
> >> assignment to ->u.addr, etc.  IOW, make it the outermost lock there.
> >
> > Hah, yes. I misunderstood you.
> >
> > Yes. In fact that fixes the problem I mentioned, rather than introducing
> > it.
> 
> So the easiest approach would seem to be to revert commit c845acb324aa
> ("af_unix: Fix splice-bind deadlock"), and then apply the lock split.
> 
> Like the attached two patches.
> 
> This is still *entirely* untested.
Tested-by: CAI Qian <caiqian@...hat.com>
> 
> Rainer?
> 
>                  Linus
>