linux-kernel - Re: [PATCH][RT] 2.6.24-rc2-rt1 drivers/dma/ioat

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Message-ID: <47435B31.2070304@yahoo.fr>
Date:	Tue, 20 Nov 2007 23:09:53 +0100
From:	trem <tremyfr@...oo.fr>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	"Nelson, Shannon" <shannon.nelson@...el.com>,
	linux-rt-users@...r.kernel.org, Linux-kernel@...r.kernel.org,
	Sven-Thorsten Dietrich <sdietrich@...ell.com>
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

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

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);
 
        ioat_chan->pending += desc_count;
        if (ioat_chan->pending >= 4) {

-
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