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Date: Wed, 30 Mar 2011 13:53:32 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Subject: Re: mmotm threatens ppc preemption again
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Cc: linuxppc-dev@lists.ozlabs.org, Jeremy Fitzhardinge <jeremy@goop.org>,
	Hugh Dickins <hughd@google.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>
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On Mon, 21 Mar 2011 13:22:30 +1100
Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:

> On Sun, 2011-03-20 at 19:20 -0700, Hugh Dickins wrote:
> > > As long as the races to avoid are between map/unmap vs. access, yes, it
> > > -should- be fine, and we used to not do demand faulting on kernel space
> > > (but for how long ?). I'm wondering why we don't just stick a ptl in
> > > there or is there a good reason why we can't ?
> > 
> > We can - but we usually prefer to avoid unnecessary locking.
> > An arch function which locks init_mm.page_table_lock on powerpc,
> > but does nothing on others? 
> 
> That still means gratuitous differences between how the normal and
> kernel page tables are handled. Maybe that's not worth bothering ...

So what will we do here?  I still have

mm-remove-unused-token-argument-from-apply_to_page_range-callback.patch
mm-add-apply_to_page_range_batch.patch
ioremap-use-apply_to_page_range_batch-for-ioremap_page_range.patch
vmalloc-use-plain-pte_clear-for-unmaps.patch
vmalloc-use-apply_to_page_range_batch-for-vunmap_page_range.patch
vmalloc-use-apply_to_page_range_batch-for-vmap_page_range_noflush.patch
vmalloc-use-apply_to_page_range_batch-in-alloc_vm_area.patch
xen-mmu-use-apply_to_page_range_batch-in-xen_remap_domain_mfn_range.patch
xen-grant-table-use-apply_to_page_range_batch.patch

floating around and at some stage they may cause merge problems.