On 03/02/2011 02:19 PM, Linus Torvalds wrote:
There are various reasons that we need to flush TLBs _after_ freeing
the page-tables themselves. For some architectures (x86 among others)
this serializes against (both hardware and software) page table
walkers like gup_fast().
This part of the changelog also makes no sense what-so-ever. It's
actively wrong.
On x86, we absolutely *must* do the TLB flush _before_ we release the
page tables. So your commentary is actively wrong and misleading.
The order has to be:
- clear the page table entry, queue the page to be free'd
- flush the TLB
- free the page (and page tables)
and nothing else is correct, afaik. So the changelog is pure and utter
garbage. I didn't look at what the patch actually changed.
The patch seems to preserve the correct behaviour.
The changelog should probably read something along the
lines of:
"There are various reasons that we need to flush TLBs _after_
clearing the page-table entries themselves."
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