Re: [PATCH] flush_cache_page while pte valid

Hugh Dickins
2002-11-12T22:52:10Z

On Tue, 12 Nov 2002, David S. Miller wrote:

> From: Hugh Dickins <hugh@veritas.com>
> Date: Tue, 12 Nov 2002 17:43:40 +0000 (GMT)
>
> Sorry, I still don't get it. If the flush_cache_page is doing something
> necessary, then won't a user access in between it and invalidating pte
> undo what was necessary? And if it's not necessary, why do we do it?
> (For better performance would be a very good reason.)
>
> If there are other writable mappings of the page, we can't swap
> it out legally.

But I'm worried about the case where this is the last writable mapping:
it seems userspace (on another CPU) can still write to it in between
the flush_cache_page and invalidation of the pte (on this CPU hoping
to swap out that page).

Hugh