Re: [PATCH] sky2: Fix WARNING: at lib/dma-debug.c:902 check_sync
From: Stephen Hemminger
Date: Wed Jan 20 2010 - 13:05:22 EST
On Wed, 20 Jan 2010 09:41:03 +0000
Jarek Poplawski <jarkao2@xxxxxxxxx> wrote:
> [ previously: Re: [PATCH] af_packet: Don't use skb after dev_queue_xmit() ]
> On Tue, Jan 19, 2010 at 05:10:13PM -0800, Stephen Hemminger wrote:
> > On Tue, 19 Jan 2010 20:01:10 -0500
> > Michael Breuer <mbreuer@xxxxxxxxxx> wrote:
> > > On 1/19/2010 5:45 PM, Jarek Poplawski wrote:
> > > > On Tue, Jan 19, 2010 at 03:06:01PM -0500, Michael Breuer wrote:
> > > >
> > > >> On 1/19/2010 2:59 PM, Jarek Poplawski wrote:
> > > >>
> > > >>> On Tue, Jan 19, 2010 at 10:47:27AM -0500, Michael Breuer wrote:
> > > >>> ...
> > > >>>
> > > >>>> Still get the warning... but now 60 bytes.
> > > >>>> Jan 19 10:43:50 mail kernel: ------------[ cut here ]------------
> > > >>>> Jan 19 10:43:50 mail kernel: WARNING: at lib/dma-debug.c:902
> > > That not only compiled, but it cleared the error as well. Additionally,
> > > I used to see a bit of a delay receiving the login prompt when first
> > > connecting to the box by ssh. That delay is gone with this patch. I'd
> > > guess that the warning wasn't quite as innocuous as I thought.
> > > Note: tested on 184.108.40.206. I'll leave this up for a bit before
> > > attempting to move back to head.
> > Seems like an underlying bug in the DMA api. Maybe it just can't
> > handle operations on partial mapping.
> > Other drivers with same problem:
> > bnx2, cassini, pcnet32, r8169, rrunner, skge, sungem, tg3,
> It seems using the same length (even without pci_unmap_len()) is
> crucial here, but I hope maintainers (added to CC) will take care.
> Btw, it's not tested yet, but it might affect CONFIG_DMAR problems.
The list of places to inspect is:
$ git grep -l sync_single_for_cpu $(git grep -l skb_copy_from_linear_data)
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