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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Tony Lindgren <tony@atomide.com>
Cc: Tejun Heo <tj@kernel.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kernfs: fix locking around kernfs_ops->release() callback
Date: Mon, 13 Feb 2017 10:22:22 -0800	[thread overview]
Message-ID: <20170213182222.GA23274@kroah.com> (raw)
In-Reply-To: <20170213175724.GH21809@atomide.com>

On Mon, Feb 13, 2017 at 09:57:25AM -0800, Tony Lindgren wrote:
> * Tejun Heo <tj@kernel.org> [170211 12:34]:
> > The release callback may be called from two places - file release
> > operation and kernfs open file draining.  kernfs_open_file->mutex is
> > used to synchronize the two callsites.  This unfortunately leads to
> > possible circular locking because of->mutex is used to protect the
> > usual kernfs operations which may use locking constructs which are
> > held while removing and thus draining kernfs files.
> > 
> > @of->mutex is for synchronizing concurrent kernfs access operations
> > and all we need here is synchronization between the releaes and drain
> > paths.  As the drain path has to grab kernfs_open_file_mutex anyway,
> > let's use the mutex to synchronize the release operation instead.
> > 
> > Signed-off-by: Tejun Heo <tj@kernel.org>
> > Reported-by: Tony Lindgren <tony@atomide.com>
> > Fixes: 0e67db2f9fe9 ("kernfs: add kernfs_ops->open/release() callbacks")
> > ---
> > Hello,
> > 
> > Tony, can you please verify that this resolves the lockdep warnings
> > that you've been seeing on linux-next?
> 
> Yes thanks this fixes the issue I was seeing:
> 
> Tested-by: Tony Lindgren <tony@atomide.com>
> 
> > Greg, this is a fix for the kernfs patches which are being routed
> > through the cgroup tree.  Once Tony confirms, I'll apply this patch on
> > top.

Great, no objection from me:

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

  reply	other threads:[~2017-02-13 18:22 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20170209003642.GY3897@atomide.com>
     [not found] ` <20170211031819.GC19050@mtj.duckdns.org>
     [not found]   ` <20170211044855.GC3897@atomide.com>
2017-02-11 20:33     ` [PATCH] kernfs: fix locking around kernfs_ops->release() callback Tejun Heo
2017-02-13 17:57       ` Tony Lindgren
2017-02-13 18:22         ` Greg Kroah-Hartman [this message]
2017-02-21 20:50       ` Tejun Heo

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