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SubjectRe: [PATCH][RT] 2.6.24-rc2-rt1 drivers/dma/ioat_dma.c compile fix
Date
From
On Nov 16, 2007 3:57 AM, Sven-Thorsten Dietrich <sdietrich@novell.com>
wrote:
> Compile fix for new code in -rc2.
>
> I'm not positive about the insertion point...
>
> Subject: compile error fix (needs review)
>
> RT changes __list_splice to require prev and next pointers.
>
> This changes the use in the new code to list_splice_tail,
> but the optimal insertion point needs to be analyzed.
>
> Signed-off-by: Sven-Thorsten Dietrich <sdietrich@suse.de>
>
> ---
> drivers/dma/ioat_dma.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-2.6.23/drivers/dma/ioat_dma.c
> ===================================================================
> --- linux-2.6.23.orig/drivers/dma/ioat_dma.c
> +++ linux-2.6.23/drivers/dma/ioat_dma.c
> @@ -244,7 +244,7 @@ static dma_cookie_t ioat_tx_submit(struc
> /* write address into NextDescriptor field of last desc in
chain */
> to_ioat_desc(ioat_chan->used_desc.prev)->hw->next =
>
first->async_tx.phys;
> - __list_splice(&new_chain, ioat_chan->used_desc.prev);
> + list_splice_tail(&new_chain, ioat_chan->used_desc.prev);
>

NAK.

These functions do insertions differently. The 'prev' is pointing to
the last valid descriptor in the queue and you really want to get the
new_chain stuck on after this. Your list_splice_tail() will insert the
new_chain just before it which will muck up the order of the DMA
requests.

You might have more success with
list_splice_tail(&new_chain, ioat_chan->used_desc);
where used_desc points to the whole list, rather than using the .prev
pointer to a specific node.

Please copy me on future ioatdma related comments.

Thanks,
sln
--
======================================================================
Mr. Shannon Nelson LAN Access Division, Intel Corp.
Shannon.Nelson@intel.com I don't speak for Intel
(503) 712-7659 Parents can't afford to be squeamish.
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