linux-kernel - Re: mmiotracer hangs the system

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Date:   Fri, 19 Aug 2016 18:35:33 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     karol herbst <karolherbst@...il.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: mmiotracer hangs the system

On Fri, Aug 19, 2016 at 6:08 PM, karol herbst <karolherbst@...il.com> wrote:
> 2016-08-19 15:02 GMT+02:00 Andy Shevchenko <andy.shevchenko@...il.com>:
>> On Fri, Aug 19, 2016 at 1:35 PM, karol herbst <karolherbst@...il.com> wrote:
>>> is there any update on that issue I missed somehow? I really don't
>>> want to leave the mmiotracer in a state, where it breaks something
>>> while fixing other issues.
>>
>> No updates. I'm busy right now with more priority tasks and revert
>> works for me. Issue is reproducible in my case 100%.
>>
>
> Is there something I could do with a "normal" haswell desktop system
> to reproduce this issue?

Try LPSS UART device(s)

>
> I'll try to play around the next days a bit and maybe I find something
> that works out here as well. It seems to be related to
> unmapping-mapping cycles.

That is the only thing I would think of.

>
> Because if this only happens with the pwm-lpss driver,

It has nothing to do with pwm-lpss since it's a HS UART and served by
intel-lpss driver.

> it may be
> really troublesome to debug, because I don't really know the code that
> well to be sure where the issue might be.
>
>> So, I would able to attach dmesg in case it would be helpful.
>> Otherwise tell me exact instructions how to debug the issue.
>>
>> Here you are:
>> http://pastebin.com/raw/VfTZENt7
>>
>>> But for now, without being able to even reproduce the issue, I can't
>>> really do much, because the code in the current state looks sane to
>>> me. Maybe this case includes the mmiotracer cleaning things up and
>>> arms new region for mmiotracing and that's why it fails? Besides that,
>>> I have no idea and no way to reproduce this, so I can't help this way.
>>
>> Maybe. First thing happened is iounmap().


-- 
With Best Regards,
Andy Shevchenko