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Date: Thu, 21 Dec 2017 12:15:31 -0600
From: Bruno Wolff III <bruno@wolff.to>
To: Jens Axboe <axboe@kernel.dk>
Cc: weiping zhang <zwp10758@gmail.com>, Laura Abbott <labbott@redhat.com>,
        Jan Kara <jack@suse.cz>, linux-mm@kvack.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        regressions@leemhuis.info,
        weiping zhang <zhangweiping@didichuxing.com>,
        linux-block@vger.kernel.org
Subject: Re: Regression with a0747a859ef6 ("bdi: add error handle for
 bdi_debug_register")
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On Thu, Dec 21, 2017 at 10:02:15 -0700,
  Jens Axboe <axboe@kernel.dk> wrote:
>On 12/21/17 9:42 AM, Bruno Wolff III wrote:
>> On Thu, Dec 21, 2017 at 23:48:19 +0800,
>>   weiping zhang <zwp10758@gmail.com> wrote:
>>>> output you want. I never saw it for any kernels I compiled myself. Only when
>>>> I test kernels built by Fedora do I see it.
>>> see it every boot ?
>>
>> I don't look every boot. The warning gets scrolled of the screen. Once I see
>> the CPU hang warnings I know the boot is failing. I don't always look
>> at journalctl later to see what's there.
>
>I'm going to revert a0747a859ef6 for now, since we're now 8 days into this
>and no progress has been made on fixing it.

One important thing I have just found is that it looks like the problem 
only happens when booting in enforcing mode. If I boot in permissive 
mode it does not happen. My home machines are currently set to boot in 
permissive mode and I'll test this evening to see if I can reproduce the 
problem if I change them to enforcing mode. If so I'll be able to do lots 
of testing during my vacation.