On Wed, 2016-12-07 at 17:31 -0600, Tyrel Datwyler wrote:
> The first byte of each CRQ entry is used to indicate whether an entry is
> a valid response or free for the VIOS to use. After processing a
> response the driver sets the valid byte to zero to indicate the entry is
> now free to be reused. Add a memory barrier after this write to ensure
> no other stores are reordered when updating the valid byte.
Which "other stores" specifically ? This smells fishy without that
precision. It's important to always understand what exactly barriers
order with.
Cheers,
Ben.
> Signed-off-by: Tyrel Datwyler <tyreld@xxxxxxxxxxxxxxxxxx>
> ---
> drivers/scsi/ibmvscsi/ibmvscsi.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
> index d9534ee..2f5b07e 100644
> --- a/drivers/scsi/ibmvscsi/ibmvscsi.c
> +++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
> @@ -232,6 +232,7 @@ static void ibmvscsi_task(void *data)
> > while ((crq = crq_queue_next_crq(&hostdata->queue)) != NULL) {
> > ibmvscsi_handle_crq(crq, hostdata);
> > crq->valid = VIOSRP_CRQ_FREE;
> > + wmb();
> > }
>
> > vio_enable_interrupts(vdev);
> @@ -240,6 +241,7 @@ static void ibmvscsi_task(void *data)
> > vio_disable_interrupts(vdev);
> > ibmvscsi_handle_crq(crq, hostdata);
> > crq->valid = VIOSRP_CRQ_FREE;
> > + wmb();
> > } else {
> > done = 1;
> > }
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