linux-kernel - Re: net/sunrpc: v4.14-rc4 lockdep warning

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Date:   Tue, 10 Oct 2017 10:19:19 -0700
From:   "tj@...nel.org" <tj@...nel.org>
To:     Trond Myklebust <trondmy@...marydata.com>
Cc:     "bfields@...ldses.org" <bfields@...ldses.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "jlayton@...chiereds.net" <jlayton@...chiereds.net>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        "jiangshanlai@...il.com" <jiangshanlai@...il.com>,
        "anna.schumaker@...app.com" <anna.schumaker@...app.com>
Subject: Re: net/sunrpc: v4.14-rc4 lockdep warning

Hello,

On Tue, Oct 10, 2017 at 04:48:57PM +0000, Trond Myklebust wrote:
> Thanks for the explanation. What I'm not really understanding here
> though, is how the work item could be queued at all. We have a
> wait_on_bit_lock() in xprt_destroy() that should mean the xprt-
> >task_cleanup work item has completed running, and that it cannot be
> requeued.
> 
> Is there a possibility that the flush_queue() might be triggered
> despite the work item not being queued?

Yeah, for sure.  The lockdep annotations don't distinguish those
cases and assume the worst case.

Thanks.

-- 
tejun