Commit 9210c075 authored May 27, 2020 by Dongli Zhang Committed by Christoph Hellwig May 27, 2020

nvme-pci: avoid race between nvme_reap_pending_cqes() and nvme_poll()



There may be a race between nvme_reap_pending_cqes() and nvme_poll(), e.g.,
when doing live reset while polling the nvme device.

      CPU X                        CPU Y
                               nvme_poll()
nvme_dev_disable()
-> nvme_stop_queues()
-> nvme_suspend_io_queues()
-> nvme_suspend_queue()
                               -> spin_lock(&nvmeq->cq_poll_lock);
-> nvme_reap_pending_cqes()
   -> nvme_process_cq()        -> nvme_process_cq()

In the above scenario, the nvme_process_cq() for the same queue may be
running on both CPU X and CPU Y concurrently.

It is much more easier to reproduce the issue when CONFIG_PREEMPT is
enabled in kernel. When CONFIG_PREEMPT is disabled, it would take longer
time for nvme_stop_queues()-->blk_mq_quiesce_queue() to wait for grace
period.

This patch protects nvme_process_cq() with nvmeq->cq_poll_lock in
nvme_reap_pending_cqes().

Fixes: fa46c6fb ("nvme/pci: move cqe check after device shutdown")
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>

parent b69e2ef2

drivers/nvme/host/pci.c

+7 −4

Original line number	Diff line number	Diff line
		@@ -1382,16 +1382,19 @@ static void nvme_disable_admin_queue(struct nvme_dev *dev, bool shutdown)

		/*
		* Called only on a device that has been disabled and after all other threads
		* that can check this device's completion queues have synced. This is the
		* last chance for the driver to see a natural completion before
		* nvme_cancel_request() terminates all incomplete requests.
		* that can check this device's completion queues have synced, except
		* nvme_poll(). This is the last chance for the driver to see a natural
		* completion before nvme_cancel_request() terminates all incomplete requests.
		*/
		static void nvme_reap_pending_cqes(struct nvme_dev *dev)
		{
		int i;

		for (i = dev->ctrl.queue_count - 1; i > 0; i--)
		for (i = dev->ctrl.queue_count - 1; i > 0; i--) {
		spin_lock(&dev->queues[i].cq_poll_lock);
		nvme_process_cq(&dev->queues[i]);
		spin_unlock(&dev->queues[i].cq_poll_lock);
		}
		}

		static int nvme_cmb_qdepth(struct nvme_dev *dev, int nr_io_queues,

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