linux-kernel - Re: [writeback] 8bc4ad9498: INFO: suspicious RCU usage. ]

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Message-ID: <20160902180051.GB18760@htj.duckdns.org>
Date:   Fri, 2 Sep 2016 14:00:51 -0400
From:   Tejun Heo <tj@...nel.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Jens Axboe <axboe@...com>,
        kernel test robot <xiaolong.ye@...el.com>, lkp@...org,
        Jens Axboe <axboe@...nel.dk>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [writeback] 8bc4ad9498: INFO: suspicious RCU usage. ]

Hello, Paul.

On Fri, Sep 02, 2016 at 10:00:56AM -0700, Paul E. McKenney wrote:
> Note that lockdep believes that the rcu_read_lock() has also been
> dropped, otherwise it would have listed it.

There isn't any actual code between rcu_read_lock() and the following
rcu deref.  That's the first thing which happens.  It looked
mysterious to me so I was wondering whether you knew any brekages on
rcu lockdep side.  Unfortunately, that doesn't seem to be the case.

> At this point, I have to suggest "git bisect"...

I'll try to reproduce it and see wth is going on.

Thanks!

-- 
tejun