Re: [REGRESSION][v4.14.y][v4.15] x86/intel_rdt/cqm: Improve limbo list processing

[Joseph Salisbury <joseph.salisbury@canonical.com>]

On 01/16/2018 08:32 AM, Shankar, Ravi V wrote:
> Vikas on vacation until end of the month. Fenghua will look into this
> issue.
>
> On Jan 16, 2018, at 5:09 AM, Thomas Gleixner <tglx@linutronix.de
> <mailto:tglx@linutronix.de>> wrote:
>
>>
>> Vikas, Fenghua can you please look at that ASAP?
>>
>> On Sun, 14 Jan 2018, Thomas Gleixner wrote:
>>
>>> On Fri, 12 Jan 2018, Joseph Salisbury wrote:
>>>
>>>> Hi Vikas,
>>>>
>>>> A kernel bug report was opened against Ubuntu [0].  After a kernel
>>>> bisect, it was found that reverting the following commit resolved
>>>> this bug:
>>>>
>>>> commit 24247aeeabe99eab13b798ccccc2dec066dd6f07
>>>> Author: Vikas Shivappa <vikas.shivappa@linux.intel.com
>>>> <mailto:vikas.shivappa@linux.intel.com>>
>>>> Date:   Tue Aug 15 18:00:43 2017 -0700
>>>>
>>>>     x86/intel_rdt/cqm: Improve limbo list processing
>>>>
>>>>
>>>> The regression was introduced as of v4.14-r1 and still exists with
>>>> current mainline.  The trace with v4.15-rc7 is in comment #44[1].
>>>>
>>>> I was hoping to get your feedback, since you are the patch author.  Do
>>>> you think gathering any additional data will help diagnose this issue,
>>>> or would it be best to submit a revert request?
>>>
>>> That stinks like a use after free. Can you run with KASAN enabled?
>>>
>>> Thanks,
>>>
>>>    tglx


Here is some data wiht KASAN enabled:
https://bugs.launchpad.net/ubuntu/+source/linux-hwe/+bug/1733662/comments/51

Are there any specific logs you would like to see, or specific actions
executed?

Thanks,

Joe