linux-kernel - RE: [PATCH 3/3] PCI: hv: delete the device earlier from hbus->children for hot-remove

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Message-ID: <DM5PR03MB24909D15D44948C4E9526848A0BC0@DM5PR03MB2490.namprd03.prod.outlook.com>
Date:   Mon, 14 Nov 2016 23:08:02 +0000
From:   KY Srinivasan <kys@...rosoft.com>
To:     Dexuan Cui <decui@...rosoft.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>
CC:     "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "Jake Oshins" <jakeo@...rosoft.com>,
        Hadden Hoppert <haddenh@...rosoft.com>,
        "Vitaly Kuznetsov" <vkuznets@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "apw@...onical.com" <apw@...onical.com>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 3/3] PCI: hv: delete the device earlier from
 hbus->children for hot-remove



> -----Original Message-----
> From: Dexuan Cui
> Sent: Wednesday, November 9, 2016 11:20 PM
> To: Bjorn Helgaas <bhelgaas@...gle.com>; linux-pci@...r.kernel.org;
> devel@...uxdriverproject.org
> Cc: gregkh@...uxfoundation.org; KY Srinivasan <kys@...rosoft.com>;
> Haiyang Zhang <haiyangz@...rosoft.com>; Stephen Hemminger
> <sthemmin@...rosoft.com>; Jake Oshins <jakeo@...rosoft.com>; Hadden
> Hoppert <haddenh@...rosoft.com>; Vitaly Kuznetsov
> <vkuznets@...hat.com>; jasowang@...hat.com; apw@...onical.com;
> olaf@...fle.de; linux-kernel@...r.kernel.org
> Subject: [PATCH 3/3] PCI: hv: delete the device earlier from hbus->children
> for hot-remove
> 
> After we send a PCI_EJECTION_COMPLETE message to the host, the host will
> immediately send us a PCI_BUS_RELATIONS message with
> relations->device_count == 0, so pci_devices_present_work(), running on
> another thread, can find the being-ejected device, mark
> the hpdev->reported_missing to true, and run list_move_tail()/list_del()
> for the device -- this races hv_eject_device_work() -> list_del().
> 
> The patch moves the list_del() in hv_eject_device_work() to an earlier
> place, i.e. before we send PCI_EJECTION_COMPLETE, so later the
> pci_devices_present_work() can't see the device.
> 
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> CC: Jake Oshins <jakeo@...rosoft.com>
> Cc: KY Srinivasan <kys@...rosoft.com>
> CC: Haiyang Zhang <haiyangz@...rosoft.com>
> CC: Vitaly Kuznetsov <vkuznets@...hat.com>

Thanks Dexuan.

Acked-by: K. Y. Srinivasan <kys@...rosoft.com>
> ---
>  drivers/pci/host/pci-hyperv.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
> index 7590ad0..fe5179d 100644
> --- a/drivers/pci/host/pci-hyperv.c
> +++ b/drivers/pci/host/pci-hyperv.c
> @@ -1582,6 +1582,10 @@ static void hv_eject_device_work(struct
> work_struct *work)
>  		pci_dev_put(pdev);
>  	}
> 
> +	spin_lock_irqsave(&hpdev->hbus->device_list_lock, flags);
> +	list_del(&hpdev->list_entry);
> +	spin_unlock_irqrestore(&hpdev->hbus->device_list_lock, flags);
> +
>  	memset(&ctxt, 0, sizeof(ctxt));
>  	ejct_pkt = (struct pci_eject_response *)&ctxt.pkt.message;
>  	ejct_pkt->message_type.type = PCI_EJECTION_COMPLETE;
> @@ -1590,10 +1594,6 @@ static void hv_eject_device_work(struct
> work_struct *work)
>  			 sizeof(*ejct_pkt), (unsigned long)&ctxt.pkt,
>  			 VM_PKT_DATA_INBAND, 0);
> 
> -	spin_lock_irqsave(&hpdev->hbus->device_list_lock, flags);
> -	list_del(&hpdev->list_entry);
> -	spin_unlock_irqrestore(&hpdev->hbus->device_list_lock, flags);
> -
>  	put_pcichild(hpdev, hv_pcidev_ref_childlist);
>  	put_pcichild(hpdev, hv_pcidev_ref_pnp);
>  	put_hvpcibus(hpdev->hbus);
> --
> 2.7.4