linux-kernel - Re: [PATCH] nvme: fix lockdep warning in nvme_mpath_clear_current

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Message-ID: <20180514133442.dyvveuxkaeithb4r@linux-x5ow.site>
Date:   Mon, 14 May 2018 15:34:42 +0200
From:   Johannes Thumshirn <jthumshirn@...e.de>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Keith Busch <keith.busch@...el.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Linux Kernel Mailinglist <linux-kernel@...r.kernel.org>,
        Linux NVMe Mailinglist <linux-nvme@...ts.infradead.org>,
        Hannes Reinecke <hare@...e.de>, Christoph Hellwig <hch@....de>
Subject: Re: [PATCH] nvme: fix lockdep warning in
 nvme_mpath_clear_current_path

On Mon, May 14, 2018 at 06:31:05AM -0700, Paul E. McKenney wrote:
> If you are just looking at the value of an RCU-protected pointer, then
> using rcu_access_pointer() will cause RCU to just read out the value
> and otherwise keeps its mouth shut.
> 
> If you use rcu_access_pointer() and later dereference the value without
> protection, you will of course get what you deserve, good and hard.  ;-)

Thanks Paul.

Christoph, I'll be sending the v2 probably tomorrow as I have more
lockdep fixes for nvme in the pipe and I'll send them out as a
complete series.

-- 
Johannes Thumshirn                                          Storage
jthumshirn@...e.de                                +49 911 74053 689
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