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

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Message-ID: <CAEiAFz00xmDPSRi+EPpYwnJPkzd1E2mDc-afDnpqtiOgKFHscQ@mail.gmail.com>
Date:   Mon, 16 Oct 2017 15:34:20 +0200
From:   Jan Glauber <jan.glauber@...il.com>
To:     Trond Myklebust <trondmy@...marydata.com>
Cc:     "tj@...nel.org" <tj@...nel.org>,
        "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

Hi Trond,

is there a patch available for this issue? I'm running into with
4.14-rc5 on my ARM64 board.

thanks, Jan

2017-10-11 19:49 GMT+02:00 Trond Myklebust <trondmy@...marydata.com>:
> On Tue, 2017-10-10 at 10:19 -0700, tj@...nel.org wrote:
>> 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.
>>
>
> OK. Let's just remove that call to cancel_work_sync() then. As I said,
> it should be redundant due to the wait_on_bit_lock().
>
> --
> Trond Myklebust
> Linux NFS client maintainer, PrimaryData
> trond.myklebust@...marydata.com