netdev - Re: possible circular locking dependency detected

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Message-ID: <CA+55aFwntZpaAutp_C=sLBg8ravfYGRoF4TTG1cfE3SjaJEOtw@mail.gmail.com>
Date:   Thu, 1 Sep 2016 15:04:38 -0700
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>
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.

Rainer?

                 Linus

View attachment "0001-Revert-af_unix-Fix-splice-bind-deadlock.patch" of type "text/x-patch" (4466 bytes)

View attachment "0002-af_unix-split-u-readlock-into-two-iolock-and-bindloc.patch" of type "text/x-patch" (6998 bytes)