netdev - Re: [PATCH 2/2] af_unix: split 'u->readlock' into two: 'iolock' and 'bindlock'

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Message-Id: <20160902.121534.1390430589343316053.davem@davemloft.net>
Date:   Fri, 02 Sep 2016 12:15:34 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     torvalds@...ux-foundation.org
Cc:     hannes@...essinduktion.org, rweikusat@...ileactivedefense.com,
        edumazet@...gle.com, w@....eu, netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] af_unix: split 'u->readlock' into two: 'iolock'
 and 'bindlock'

From: Linus Torvalds <torvalds@...ux-foundation.org>
Date: Fri, 2 Sep 2016 11:17:18 -0700

> Oh, this was missing a
> 
>   Reported-and-tested-by: CAI Qian <caiqian@...hat.com>
> 
> who found the new deadlock.
> 
> There's now *another* lockdep deadlock report by him, but that one has
> nothing to do with networking.
> 
> (And neither of these deadlocks will actually deadlock the machine in
> practice, but you can trigger the lockdep reports with some odd splice
> patterns and overlayfs use)

I read over this and can't find any problems.

The main thing I was concerned about was an I/O path that really
expects the socket's hash not to change for whatever reason, but even
all of the unix_find_other() calls are done outside of the mutex
already.