linux-kernel - Re: mmiotracer hangs the system

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Message-ID: <CAEXux-ZY6GBWOHSY4dPoNXs9iA_iXqqAk=6hHuF06R4U2sQzLw@mail.gmail.com>
Date:   Sat, 19 Nov 2016 11:56:22 +0100
From:   Karol Herbst <karolherbst@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...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

this is odd, I found a bug related to nouveau (modprobe/bind doesn't
return), but that isn't related to your issue at all or maybe it is
exactly this, cause the binding of the device doesn't return and
depending on the kind of driver, it would hang the system... yeah,
maybe it is the same issue.

anyway, could you try to trace with the attached patch? Maybe the
additional output would help me to verify it. Currently I am working
on the bugfix I mentioned above and this may also fix your issue. I
was still able to get a working mmiotrace file, even if the dvice
binding didn't finish. Is this the same for you? (try cat
"/sys/kernel/debug/tracing/trace_pipe > some_file"; and see if this
contains anything usefull).

This really looks like an odd issue, because the mmiotracer still
behaves as expected.

2016-10-22 18:02 GMT+02:00 Andy Shevchenko <andy.shevchenko@...il.com>:
> On Fri, Oct 14, 2016 at 12:12 AM, Karol Herbst <karolherbst@...il.com> wrote:
>> sorry for the delay fixing that bug. I got occupied with other things
>> and didn't really got to the issue again, it is on my todo list as the
>> next item though and I hope I will be able to get a fix ready this
>> weekend. I think I might know where the issue is, but didn't confirm
>> it yet.
>
> Thanks.I'm still using revert. Feel free to Cc me when you will have
> some material to test.
>
>>
>> Again, sorry for the delay.
>>
>> Karol
>>
>> 2016-08-19 22:46 GMT+02:00 Karol Herbst <karolherbst@...il.com>:
>>> Hi again,
>>>
>>> I was able to get a crash/freeze/something while unbinding/binding my
>>> nvidia gpu from nouveau.
>>>
>>> Guess that means something is odd. I will investigate this more over
>>> the weekend.
>>>
>>> 2016-08-19 17:35 GMT+02:00 Andy Shevchenko <andy.shevchenko@...il.com>:
>>>> 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
>
>
>
> --
> With Best Regards,
> Andy Shevchenko