From mboxrd@z Thu Jan  1 00:00:00 1970
From: bvanassche@acm.org (Bart Van Assche)
Date: Mon, 22 Jul 2019 11:26:57 -0700
Subject: [PATCH] nvme-pci: fix probe and remove race
In-Reply-To: <20190719194256.23618-1-sagi@grimberg.me>
References: <20190719194256.23618-1-sagi@grimberg.me>
Message-ID: <ef8149f9-b7e0-d2ba-6bcb-ff51d8e2a908@acm.org>

On 7/19/19 12:42 PM, Sagi Grimberg wrote:
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index 4b508d5e45cf..50061abe49c6 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -127,6 +127,7 @@ struct nvme_dev {
>   	dma_addr_t host_mem_descs_dma;
>   	struct nvme_host_mem_buf_desc *host_mem_descs;
>   	void **host_mem_desc_bufs;
> +	async_cookie_t async_probe;
>   };
>   
>   static int io_queue_depth_set(const char *val, const struct kernel_param *kp)
> @@ -2765,7 +2766,7 @@ static int nvme_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>   	dev_info(dev->ctrl.device, "pci function %s\n", dev_name(&pdev->dev));
>   
>   	nvme_get_ctrl(&dev->ctrl);
> -	async_schedule(nvme_async_probe, dev);
> +	dev->async_probe = async_schedule(nvme_async_probe, dev);
>   
>   	return 0;
>   
> @@ -2810,6 +2811,8 @@ static void nvme_remove(struct pci_dev *pdev)
>   {
>   	struct nvme_dev *dev = pci_get_drvdata(pdev);
>   
> +	/* wait for async probe to complete */
> +	async_synchronize_cookie(dev->async_probe + 1);
>   	nvme_change_ctrl_state(&dev->ctrl, NVME_CTRL_DELETING);
>   	pci_set_drvdata(pdev, NULL);

Hi Sagi,

Does the async_synchronize_cookie() call wait until all previously 
started probes have finished? In other words, does the change in 
nvme_remove() introduce a dependency between probe and remove calls of 
different NVMe devices? Is that dependency important? If not, can it be 
avoided to introduce that dependency?

Thanks,

Bart.