Re: [PATCH] ibmvscsi: add write memory barrier to CRQ processing
From: Benjamin Herrenschmidt <hidden>
Date: 2016-12-09 21:20:58
Also in:
linux-scsi
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.
quoted hunk ↗ jump to hunk
Signed-off-by: Tyrel Datwyler <redacted> --- 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)quoted
while ((crq = crq_queue_next_crq(&hostdata->queue)) != NULL) { ibmvscsi_handle_crq(crq, hostdata); crq->valid = VIOSRP_CRQ_FREE; + wmb(); }quoted
vio_enable_interrupts(vdev);@@ -240,6 +241,7 @@ static void ibmvscsi_task(void *data)quoted
vio_disable_interrupts(vdev); ibmvscsi_handle_crq(crq, hostdata); crq->valid = VIOSRP_CRQ_FREE; + wmb(); } else { done = 1; }