linux-kernel - Re: [BUG] kernel BUG at mm/vmacache.c:85!

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Message-ID: <535F5C7F.3000608@linux.vnet.ibm.com>
Date:	Tue, 29 Apr 2014 13:32:07 +0530
From:	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
To:	Davidlohr Bueso <davidlohr@...com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux MM <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Rik van Riel <riel@...hat.com>,
	Michel Lespinasse <walken@...gle.com>,
	Hugh Dickins <hughd@...gle.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: [BUG] kernel BUG at mm/vmacache.c:85!

On 04/29/2014 04:09 AM, Davidlohr Bueso wrote:
> Adding Oleg.
> 
> On Mon, 2014-04-28 at 14:55 -0700, Linus Torvalds wrote:
>> On Mon, Apr 28, 2014 at 2:20 PM, Linus Torvalds
>> <torvalds@...ux-foundation.org> wrote:
>>>
>>> That said, the bug does seem to be that some path doesn't invalidate
>>> the vmacache sufficiently, or something inserts a vmacache entry into
>>> the current process when looking up a remote process or whatever.
>>> Davidlohr, ideas?
>>
>> Maybe we missed some use_mm() call. That will change the current mm
>> without flushing the vma cache. The code considers kernel threads to
>> be bad targets for vma caching for this reason (and perhaps others),
>> but maybe we missed something.
>>
>> I wonder if we should just invalidate the vma cache in use_mm(), and
>> remote the "kernel tasks are special" check.
>>
>> Srivatsa, are you doing something peculiar on that system that would
>> trigger this? I see some kdump failures in the log, anything else?
> 
> Is this perhaps a KVM guest? fwiw I see CONFIG_KVM_ASYNC_PF=y which is a
> user of use_mm().
> 

No, this is just running baremetal on x86. I copied the kernel config
of a distro kernel and reused it.

Regards,
Srivatsa S. Bhat

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