nvme-pci: remove the barriers in nvme_irq()

The barriers were added to the nvme_irq() in 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@gmail.com>
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 7249ae7..2d5496c 100644 (file)
--- 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;
 }