Hello Linus,
Attached is a patch to move the call of flush_cache_page before
clearing PTE in vmscan.c:try_to_swap_out.
Here, we want to flush cache entries written from user space.
But for some archtecture, we need valid PTE to flush, so, we need to
call flush_cache_page before ptep_get_and_clear.
At least, we need this for SuperH (which has virtually indexed
physically tagged cache).
--- v2.4.8-pre4/mm/vmscan.c Sat Aug 4 15:37:55 2001
+++ linux/mm/vmscan.c Sat Aug 4 19:27:07 2001
@@ -65,6 +65,7 @@ static void try_to_swap_out(struct mm_st
* is needed on CPUs which update the accessed and dirty
* bits in hardware.
*/
+ flush_cache_page(vma, address);
pte = ptep_get_and_clear(page_table);
flush_tlb_page(vma, address);
@@ -102,7 +103,6 @@ drop_pte:
* Basically, this just makes it possible for us to do
* some real work in the future in "refill_inactive()".
*/
- flush_cache_page(vma, address);
if (!pte_dirty(pte))
goto drop_pte;
--------
David S. Miller wrote:
> NIIBE Yutaka writes:
> > When it is called from vmscan.c:try_to_swap_out, as the PTE is cleared
> > to be zero, we have no way to know what phisical address to match.
>
> That is really an error, and it is only because the last time the
> logic try_to_swap_out() logic got rearranges the cache flush got moved
> lower down.
>
> In fact, several architectures will take a fatal trap due to
> this sequence. On these systems the tlb must be able to translate the
> virtual address given to it for the flush, and that translation must
> be valid.
>
> Thus, the code there should be:
>
> flush_cache_page(vma, address);
> pte = ptep_get_and_clear(page_table);
> flush_tlb_page(vma, address);
>
> And the flush_cache_page() further down in that function then can be
> removed.
>
> Feel free to send this fix to Linus. It is probably causing
> HyperSparc sparc32 to fail to work at all once a swap happens,
> if platforms using that chip work at all.
-- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Tue Aug 07 2001 - 21:00:32 EST