[PATCH][RT] 2.6.24-rc5-rt1 drivers/dma/ioat_dma.c compile fix

From: Sven-Thorsten Dietrich
Date: Fri Dec 14 2007 - 22:56:34 EST


Hi Steve,

looks like this patch didn't make it into 2.6.23-rc5-rt1.

I refreshed Trem's final version - please review and include in the next
RT release.

Thanks

Sven



On Tue, 2007-11-20 at 23:09 +0100, trem wrote:
> Steven Rostedt wrote:
> > On Fri, 16 Nov 2007, Nelson, Shannon wrote:
> >> 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.
> >>
> >

> Hi
>
> I've tried this change, but it still don't compile. So I propose this patch.
>
> regards,
> trem


From: trem <tremyfr@xxxxxxxx>
Subject: Re: [PATCH][RT] 2.6.24-rc2-rt1 drivers/dma/ioat_dma.c compile fix

Steven Rostedt wrote:
> On Fri, 16 Nov 2007, Nelson, Shannon wrote:
>> 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.
>>
>
> And people wonder why we post RT related patches to LKML. This is exactly
> why!
>
> Thanks for the response Shannon!
>
> -- Steve
>

Hi

I've tried this change, but it still don't compile. So I propose this patch.

regards,
trem

Acked-by: Sven-Thorsten Dietrich <sdietrich@xxxxxxx>

------------------------

---
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
@@ -260,7 +260,7 @@ static dma_cookie_t ioat1_tx_submit(stru
/* 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(&new_chain, &ioat_chan->used_desc);

ioat_chan->dmacount += desc_count;
ioat_chan->pending += desc_count;



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