From: Ed Tomlinson <edt@aei.ca>
To: Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: Linux 2.6.35.2
Date: Sat, 14 Aug 2010 15:47:08 -0400
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Cc: sedat.dilek@gmail.com, Greg KH <gregkh@suse.de>,
        LKML <linux-kernel@vger.kernel.org>, penberg@kernel.org, arthur@psw.ro,
        wylda@volny.cz
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On Saturday 14 August 2010 14:47:45 Linus Torvalds wrote:
> On Sat, Aug 14, 2010 at 11:27 AM, Ed Tomlinson <edt@aei.ca> wrote:
> >
> > It seems to be helping here.  Without it 35.2 would either stall in boot or give lots of tracebacks.  With it things
> > start normally and my background stuff works as expected.
> 
> Ok, thanks. I've committed it to the -git tree.
> 
> Just to verify: you have CONFIG_HIGHPTE enabled on a x86-32 kernel,
> right? I'd have expected this to not ever show up anywhere else, and
> I'm just verifying that there isn't anything else going on. I'm
> appending the commit message, the patch hasn't changed.

No.  I have a x86-64 based kernel (amd64).

Ed

> Author: Linus Torvalds <torvalds@linux-foundation.org>
> Date:   Sat Aug 14 11:44:56 2010 -0700
> 
>     mm: fix page table unmap for stack guard page properly
> 
>     We do in fact need to unmap the page table _before_ doing the whole
>     stack guard page logic, because if it is needed (mainly 32-bit x86 with
>     PAE and CONFIG_HIGHPTE, but other architectures may use it too) then it
>     will do a kmap_atomic/kunmap_atomic.
> 
>     And those kmaps will create an atomic region that we cannot do
>     allocations in.  However, the whole stack expand code will need to do
>     anon_vma_prepare() and vma_lock_anon_vma() and they cannot do that in an
>     atomic region.
> 
>     Now, a better model might actually be to do the anon_vma_prepare() when
>     _creating_ a VM_GROWSDOWN segment, and not have to worry about any of
>     this at page fault time.  But in the meantime, this is the
>     straightforward fix for the issue.
> 
>     See https://bugzilla.kernel.org/show_bug.cgi?id=16588 for details.
> 
>     Reported-by: Wylda <wylda@volny.cz>
>     Reported-by: Sedat Dilek <sedat.dilek@gmail.com>
>     Reported-by: Mike Pagano <mpagano@gentoo.org>
>     Reported-by: Fran?ois Valenduc <francois.valenduc@tvcablenet.be>
>     Tested-by: Ed Tomlinson <edt@aei.ca>
>     Cc: Pekka Enberg <penberg@kernel.org>
>     Cc: Greg KH <gregkh@suse.de>
>     Cc: stable@kernel.org
>     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
> 
>  mm/memory.c |   13 ++++++-------
>  1 files changed, 6 insertions(+), 7 deletions(-)
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