In article <Pine.LNX.4.21.0103181122480.13050-100000@imladris.rielhome.conectiva>,
Rik van Riel <riel@conectiva.com.br> wrote:
>
>OK, I'll write some code to prevent multiple threads from
>stepping all over each other when they pagefault at the
>same address.
>
>What would be the preferred method of fixing this ?
>
>- fixing do_swap_page and all ->nopage functions
There is no need to fix gthe "nopage" functions. They never see the page
table directly anyway.
So the only thing that _should_ be needed is to make sure that
do_no_page(), do_swap_page() and do_anonymous_page() will re-aquire the
mm->page_table_lock and undo their work if it turns out that the page
table entry is no longer empty..
(do_wp_page() should already be ok in this regard - it already does this
exactly because present pagetable entries can already race with kswapd.
What we're adding is that _nonpresent_ page table entries can race with
multiple invocations of concurrent page faults)
>- hacking handle_mm_fault to make sure no overlapping
> pagefaults will be served at the same time
No. The whole reason the rw_semaphores were done in the first place was
to allow page faults to happen concurrently to allow threaded
applictions to scale up even when faulting.
Linus
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This archive was generated by hypermail 2b29 : Fri Mar 23 2001 - 21:00:11 EST