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List:       linuxppc-embedded
Subject:    RE: [PATCH v7 1/8] Talitos: Support for async_tx XOR offload
From:       Liu Qiang-B32616 <B32616 () freescale ! com>
Date:       2012-08-31 10:41:08
Message-ID: BCB48C05FCE8BC4D9E61E841ECBE6DB70FDD90 () 039-SN2MPN1-011 ! 039d ! mgd ! msft ! net
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> -----Original Message-----
> From: Geanta Neag Horia Ioan-B05471
> Sent: Friday, August 31, 2012 6:39 PM
> To: Liu Qiang-B32616; linux-crypto@vger.kernel.org;
> dan.j.williams@gmail.com; herbert@gondor.hengli.com.au;
> davem@davemloft.net; linux-kernel@vger.kernel.org; linuxppc-
> dev@lists.ozlabs.org
> Cc: Li Yang-R58472; Phillips Kim-R1AAHA; vinod.koul@intel.com; Dan
> Williams; arnd@arndb.de; gregkh@linuxfoundation.org
> Subject: RE: [PATCH v7 1/8] Talitos: Support for async_tx XOR offload
> 
> On Fri, 31 Aug 2012 06:08:05 +0300, Liu Qiang-B32616
> <B32616@freescale.com>
> wrote:
> > > -----Original Message-----
> > > From: Geanta Neag Horia Ioan-B05471
> > > Sent: Thursday, August 30, 2012 10:23 PM
> > > To: Liu Qiang-B32616; linux-crypto@vger.kernel.org;
> > > dan.j.williams@gmail.com; herbert@gondor.hengli.com.au;
> > > davem@davemloft.net; linux-kernel@vger.kernel.org; linuxppc-
> > > dev@lists.ozlabs.org
> > > Cc: Li Yang-R58472; Phillips Kim-R1AAHA; vinod.koul@intel.com;
> > > dan.j.williams@intel.com; arnd@arndb.de; gregkh@linuxfoundation.org;
> Liu
> > > Qiang-B32616
> > > Subject: RE: [PATCH v7 1/8] Talitos: Support for async_tx XOR offload
> > >
> > > On Thu, 9 Aug 2012 11:20:48 +0300, qiang.liu@freescale.com wrote:
> > > > From: Qiang Liu <qiang.liu@freescale.com>
> > > >
> > > > Expose Talitos's XOR functionality to be used for RAID parity
> > > > calculation via the Async_tx layer.
> > > >
> > > > Cc: Herbert Xu <herbert@gondor.apana.org.au>
> > > > Cc: David S. Miller <davem@davemloft.net>
> > > > Signed-off-by: Dipen Dudhat <Dipen.Dudhat@freescale.com>
> > > > Signed-off-by: Maneesh Gupta <Maneesh.Gupta@freescale.com>
> > > > Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
> > > > Signed-off-by: Vishnu Suresh <Vishnu@freescale.com>
> > > > Signed-off-by: Qiang Liu <qiang.liu@freescale.com>
> > > > ---
> > > >  drivers/crypto/Kconfig   |    9 +
> > > >  drivers/crypto/talitos.c |  413
> > > ++++++++++++++++++++++++++++++++++++++++++++++
> > > >  drivers/crypto/talitos.h |   53 ++++++
> > > >  3 files changed, 475 insertions(+), 0 deletions(-)
> > >
> 
> > > > +static int talitos_alloc_chan_resources(struct dma_chan *chan)
> > > > +{
> > > > +	struct talitos_xor_chan *xor_chan;
> > > > +	struct talitos_xor_desc *desc;
> > > > +	LIST_HEAD(tmp_list);
> > > > +	int i;
> > > > +
> > > > +	xor_chan = container_of(chan, struct talitos_xor_chan,
> common);
> > > > +
> > > > +	if (!list_empty(&xor_chan->free_desc))
> > > > +		return xor_chan->total_desc;
> > > > +
> > > > +	for (i = 0; i < TALITOS_MAX_DESCRIPTOR_NR; i++) {
> > > > +		desc = talitos_xor_alloc_descriptor(xor_chan,
> > > > +				GFP_KERNEL | GFP_DMA);
> > >
> > > talitos_xor_alloc_descriptor() is called here without holding
> > > the xor_chan->desc_lock and it increments xor_chan->total_desc.
> > > Isn't this an issue ?
> >
> > No, please refer to the code as below,
> > +	list_add_tail(&desc->node, &tmp_list);
> >
> > The list is temporary list, it will be merged to xor_chan->free_desc in
> next step, here is protected
> > by lock,
> > +	spin_lock_bh(&xor_chan->desc_lock);
> > +	list_splice_init(&tmp_list, &xor_chan->free_desc);
> > +	spin_unlock_bh(&xor_chan->desc_lock);
> 
> I was not referring to the list, but to xor_chan->total_desc variable.
> The following access:
> talitos_alloc_chan_resources()->talitos_xor_alloc_descriptor()-
> >total_desc++
> is not protected by the xor_chan->desc_lock.
Ok, I will correct it in next series. Thanks.


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