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SubjectRe: Linux-2.5.17
On Mon, May 20, 2002 at 10:16:35PM -0700, Linus Torvalds wrote:
> Various FS updates (including merges of quota and iget_locked), and
> Makefile cleanups from Kai.
>
> And yet more TLB shootdown stuff.

We seem to have inconsistent cache handling in the new TLB shootdown stuff.
Or maybe its just my misunderstanding of what's going on; whatever it is,
the new TLB shootdown stuff appears to be quite messy.

Lets look at the flow of the 3 places where tlb_gather_mmu is used:

zap_page_range unmap_region exit_mmap
flush_cache_range tlb_gather_mmu tlb_gather_mmu
tlb_gather_mmu unmap_page_range flush_cache_mm
unmap_page_range free_pgtables unmap_page_range
tlb_finish_mmu tlb_finish_mmu clear_page_tables
tlb_finish_mmu

So we have 3 different functions, 2 different orders of gather_mmu
and cache handling, and one with no cache handling what so ever.

I think we have two options - either leave the cache handling up to
tlb_start_vma() (in which case, flush_cache_range and flush_cache_mm
are redundant and should be removed) or let it be up to the caller
of tlb_gather_mmu to call the right cache handling function.

I think which is actually function dependent - in zap_page_range,
we're only removing one vma. In exit_mmap, we're removing all vmas.
In unmap_region, we're removing an unspecified number of vmas.
Depending on which option we choose, we'll either end up calling
flush_cache_range() many times, or flush_cache_mm() and flushing
the cache for a munmap of a small area.

--
Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux
http://www.arm.linux.org.uk/personal/aboutme.html

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