linux-kernel - Re: [PATCH] mm: add pte_present() check on existing hugetlb

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Message-ID: <5317FA3B.8060900@oracle.com>
Date:	Wed, 05 Mar 2014 23:31:55 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
CC:	akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, riel@...hat.com
Subject: Re: [PATCH] mm: add pte_present() check on existing hugetlb_entry
 callbacks

On 03/04/2014 06:49 PM, Naoya Horiguchi wrote:
> On Tue, Mar 04, 2014 at 05:46:52PM -0500, Sasha Levin wrote:
>> On 03/04/2014 04:32 PM, Naoya Horiguchi wrote:
>>> # sorry if duplicate message
>>>
>>> On Mon, Mar 03, 2014 at 04:38:41PM -0500, Sasha Levin wrote:
>>>> On 03/03/2014 03:06 PM, Sasha Levin wrote:
>>>>> On 03/03/2014 12:02 AM, Naoya Horiguchi wrote:
>>>>>> Hi Sasha,
>>>>>>
>>>>>>>> I can confirm that with this patch the lockdep issue is gone. However, the NULL deref in
>>>>>>>> walk_pte_range() and the BUG at mm/hugemem.c:3580 still appear.
>>>>>> I spotted the cause of this problem.
>>>>>> Could you try testing if this patch fixes it?
>>>>>
>>>>> I'm seeing a different failure with this patch:
>>>>
>>>> And the NULL deref still happens.
>>>
>>> I don't yet find out the root reason why this issue remains.
>>> So I tried to run trinity myself but the problem didn't reproduce.
>>> (I did simply like "./trinity --group vm --dangerous" a few hours.)
>>> Could you show more detail or tips about how the problem occurs?
>>
>> I run it as root in a disposable vm, that may be the difference here.
> 
> Sorry, I didn't write it but I also run it as root on VM, so condition is
> the same. It might depend on kernel config, so I'm now trying the config
> you previously gave me, but it doesn't boot correctly on my environment
> (panic in initialization). I may need some time to get over this.

I'd be happy to help with anything off-list, it shouldn't be too difficult
to get that kernel to boot :)

I've also reverted the page walker series for now, it makes it impossible
to test anything else since it seems that hitting one of the issues is quite
easy.


Thanks,
Sasha

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