[PATCH V2 1/2] nvme-pci; remove the barriers nvme_irq()

[Chaitanya Kulkarni]

The barriers were added to the nvme_irq() in the
commit 3a7afd8ee42a ("nvme-pci: remove the CQ lock for interrupt driven queues")
to prevent compiler from doing memory optimization for the variabes that
were protected previously by spinlock in nvme_irq() at completion queue
processing and with queue head check condition..

The variable nvmeq->last_cq_head from those checks was removed in the
commit f6c4d97b0d82 ("nvme/pci: Remove last_cq_head") that was not
allwing poll queues from mistakenly triggering the spurious interrupt
detection.

Remove the barriers which were protecting the updates to the variables.

Reported-by: Heiner Kallweit <hkallweit1 at gmail.com>
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni at wdc.com>
Reviewed-by: Heiner Kallweit <hkallweit1 at gmail.com>
---
 drivers/nvme/host/pci.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 0045c5edf629..3729775f6a8a 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1062,14 +1062,8 @@ static irqreturn_t nvme_irq(int irq, void *data)
 	struct nvme_queue *nvmeq = data;
 	irqreturn_t ret = IRQ_NONE;
 
-	/*
-	 * The rmb/wmb pair ensures we see all updates from a previous run of
-	 * the irq handler, even if that was on another CPU.
-	 */
-	rmb();
 	if (nvme_process_cq(nvmeq))
 		ret = IRQ_HANDLED;
-	wmb();
 
 	return ret;
 }
-- 
2.22.1