[PATCHv3 1/4] nvme/pci: Disable interrupts for threaded handler

[Keith Busch <kbusch@kernel.org>]

The nvme driver had always left the device in a state capable of sending
more interrupts while completions were being handled in the thread.
Re-entering the primary handler disrupts the threaded handler since
they run on the same CPU. The primary handler may also be detected as
spurious when it returns IRQ_WAKE_THREAD if the threaded handler does
not finish frequently enough due to completing many requests.

Disable the irq to ensure the primary handler will not be re-entered while
the threaded handler is running. Use the nvme specific interrupt mask
set/clear registers for MSI and legacy, and rely on the irq_flow_handler
to mask the interrupt for MSIx.

Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 drivers/nvme/host/pci.c | 26 ++++++++++++++++++++++----
 1 file changed, 22 insertions(+), 4 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 365a2ddbeaa7..a0138e3ca0b9 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1036,12 +1036,30 @@ static irqreturn_t nvme_irq(int irq, void *data)
 	return ret;
 }
 
+static irqreturn_t nvme_irq_thread(int irq, void *data)
+{
+	struct nvme_queue *nvmeq = data;
+	irqreturn_t ret = nvme_irq(irq, data);
+
+	if (!to_pci_dev(nvmeq->dev->dev)->msix_enabled)
+		writel(1 << nvmeq->cq_vector, nvmeq->dev->bar + NVME_REG_INTMC);
+
+	enable_irq(irq);
+	return ret;
+}
+
 static irqreturn_t nvme_irq_check(int irq, void *data)
 {
 	struct nvme_queue *nvmeq = data;
-	if (nvme_cqe_pending(nvmeq))
-		return IRQ_WAKE_THREAD;
-	return IRQ_NONE;
+
+	if (!nvme_cqe_pending(nvmeq))
+		return IRQ_NONE;
+
+	if (!to_pci_dev(nvmeq->dev->dev)->msix_enabled)
+		writel(1 << nvmeq->cq_vector, nvmeq->dev->bar + NVME_REG_INTMS);
+
+	disable_irq_nosync(irq);
+	return IRQ_WAKE_THREAD;
 }
 
 /*
@@ -1499,7 +1517,7 @@ static int queue_request_irq(struct nvme_queue *nvmeq)
 
 	if (use_threaded_interrupts) {
 		return pci_request_irq(pdev, nvmeq->cq_vector, nvme_irq_check,
-				nvme_irq, nvmeq, "nvme%dq%d", nr, nvmeq->qid);
+			nvme_irq_thread, nvmeq, "nvme%dq%d", nr, nvmeq->qid);
 	} else {
 		return pci_request_irq(pdev, nvmeq->cq_vector, nvme_irq,
 				NULL, nvmeq, "nvme%dq%d", nr, nvmeq->qid);
-- 
2.21.0


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