linux-kernel - Re: [PATCH v0] Crypto: Talitos: re-initialize async

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Date:	Tue, 15 Dec 2009 00:29:20 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Vishnu Suresh <Vishnu@...escale.com>
Cc:	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	linux-raid@...r.kernel.org, linux-crypto@...r.kernel.org,
	herbert@...dor.apana.org.au, B04825@...escale.com,
	R58472@...escale.com
Subject: Re: [PATCH v0] Crypto: Talitos: re-initialize async_tx descriptors

On Mon, Dec 14, 2009 at 6:33 AM, Vishnu Suresh <Vishnu@...escale.com> wrote:
> The async_tx descriptors contains dangling pointers.
> Hence, re-initialize them to NULL before use.
>
> Signed-off-by: Vishnu Suresh <Vishnu@...escale.com>
> ---
> o. Rebased to linux-next as of 20091214
>
>  drivers/crypto/talitos.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/crypto/talitos.c b/drivers/crypto/talitos.c
> index 87f06be..9e261c6 100644
> --- a/drivers/crypto/talitos.c
> +++ b/drivers/crypto/talitos.c
> @@ -952,6 +952,9 @@ static struct dma_async_tx_descriptor * talitos_prep_dma_xor(
>                return NULL;
>        }
>        dma_async_tx_descriptor_init(&new->async_tx, &xor_chan->common);
> +       new->async_tx.parent = NULL;
> +       new->async_tx.next = NULL;
> +
>
>        desc = &new->hwdesc;
>        /* Set destination: Last pointer pair */

These two values are owned by the async_tx api, drivers are not
supposed to touch them.  Both iop_adma and the new ppx4xx driver
(which use the async_tx channel switching capability) get away without
touching these fields which makes me suspect there is a
misunderstanding/bug somewhere else in the talitos implementation.
Also that dma_async_tx_descriptor_init() is unexpected in the hot
path, it's only needed at initial descriptor allocation.  End result I
think this driver needs some more time to brew.

--
Dan
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