From mboxrd@z Thu Jan  1 00:00:00 1970
From: Al Viro <viro@ZenIV.linux.org.uk>
Subject: Re: possible circular locking dependency detected
Date: Fri, 2 Sep 2016 18:53:48 +0100
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Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        CAI Qian <caiqian@redhat.com>,
        Miklos Szeredi <miklos@szeredi.hu>,
        Hannes Frederic Sowa <hannes@stressinduktion.org>,
        Eric Sandeen <esandeen@redhat.com>,
        Network Development <netdev@vger.kernel.org>
To: Rainer Weikusat <rweikusat@cyberadapt.com>
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On Fri, Sep 02, 2016 at 06:40:59PM +0100, Rainer Weikusat wrote:

> The original deadlock occurred because of some code path locking the
> superblock followed by trying to acquire the af_unix readlock while

Not even that - one code path takes ->readlock under pipe lock, while
another takes pipe lock under sb_start_write...