Linux-NVME Archive on lore.kernel.org
 help / color / Atom feed
* [RFC] nvme-pci does not disable interrupt-source in threaded mode
@ 2019-11-26 20:28 Sebastian Andrzej Siewior
  2019-11-26 22:28 ` Keith Busch
  0 siblings, 1 reply; 2+ messages in thread
From: Sebastian Andrzej Siewior @ 2019-11-26 20:28 UTC (permalink / raw)
  To: linux-nvme
  Cc: Keith Busch, Jens Axboe, Thomas Gleixner, Christoph Hellwig,
	Sagi Grimberg

From drivers/nvme/host/pci.c:
| static int queue_request_irq(struct nvme_queue *nvmeq)
| {
|         struct pci_dev *pdev = to_pci_dev(nvmeq->dev->dev);
|         int nr = nvmeq->dev->ctrl.instance;
| 
|         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_check() checks if an interrupt is pending and does not disable
interrupt source if the interrupt is pending. It simply wakes the thread.
This works because the MSI-IRQ-controller is handled as edge and it does
not re-trigger. Should the IRQ fallback to non-MSI it would become LEVEL
and will keep the IRQ-line asserted so the threaded handler will no be reached.

One of these should be done:
- remove "use_threaded_interrupts" and rely simply on the "threadirqs"
  kernel command line.
- Let nvme_irq_check() disable the IRQ-source and nvme_irq() should
  enable it again once done.
- Pass IRQF_ONESHOT as irqflags.

Side note:
 msix_request_rcd_irq() (drivers/infiniband/hw/hfi1/msix.c) provides also
 both handlers and (according to the comment) receive_context_interrupt()
 disables the source before waking the thread. This one is fine and I
 did not find more users of pci_request_irq() providing both handlers.

Sebastian

_______________________________________________
linux-nvme mailing list
linux-nvme@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-nvme

^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, back to index

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-11-26 20:28 [RFC] nvme-pci does not disable interrupt-source in threaded mode Sebastian Andrzej Siewior
2019-11-26 22:28 ` Keith Busch

Linux-NVME Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-nvme/0 linux-nvme/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-nvme linux-nvme/ https://lore.kernel.org/linux-nvme \
		linux-nvme@lists.infradead.org
	public-inbox-index linux-nvme

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.infradead.lists.linux-nvme


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git