From: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>
Date: Wed, 7 Dec 2016 23:31:26 +0000 (-0600)
Subject: scsi: ibmvscsi: add write memory barrier to CRQ processing
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=b39205d248b9c3ce0548859ed786badb2e0db0bd;p=linux-beck.git

scsi: ibmvscsi: add write memory barrier to CRQ processing

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.

Signed-off-by: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>
Reviewed-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
---

diff --git a/drivers/scsi/ibmvscsi/ibmvscsi.c b/drivers/scsi/ibmvscsi/ibmvscsi.c
index 7752656c3d21..50cd01165e35 100644
--- a/drivers/scsi/ibmvscsi/ibmvscsi.c
+++ b/drivers/scsi/ibmvscsi/ibmvscsi.c
@@ -233,6 +233,7 @@ 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);
@@ -241,6 +242,7 @@ static void ibmvscsi_task(void *data)
 			vio_disable_interrupts(vdev);
 			ibmvscsi_handle_crq(crq, hostdata);
 			crq->valid = VIOSRP_CRQ_FREE;
+			wmb();
 		} else {
 			done = 1;
 		}