[PATCH 2/2 v3] pci-hyperv: lock pci bus on device eject

[KY Srinivasan]

> -----Original Message-----
> From: Long Li
> Sent: Monday, October 3, 2016 11:43 PM
> To: KY Srinivasan <kys at microsoft.com>; Haiyang Zhang
> <haiyangz at microsoft.com>; Bjorn Helgaas <bhelgaas at google.com>
> Cc: devel at linuxdriverproject.org; linux-pci at vger.kernel.org; linux-
> kernel at vger.kernel.org; Long Li <longli at microsoft.com>
> Subject: [PATCH 2/2 v3] pci-hyperv: lock pci bus on device eject
> 
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> 
> From: Long Li <longli at microsoft.com>
> 
> A PCI_EJECT message can arrive at the same time we are calling
> pci_scan_child_bus in the workqueue for the previous PCI_BUS_RELATIONS
> message or in create_root_hv_pci_bus(), in this case we could potentailly
> modify the bus from multiple places. Properly lock the bus access.
> 
> Thanks Dexuan Cui <decui at microsoft.com> for pointing out the race
> condition in create_root_hv_pci_bus().
> 
> Signed-off-by: Long Li <longli at microsoft.com>
> Tested-by: Cathy Avery <cavery at redhat.com>
> Reported-by: Xiaofeng Wang <xiaofwan at redhat.com>

Acked-by: KY Srinivasan <kys at microsoft.com>

> ---
>  drivers/pci/host/pci-hyperv.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
> index 4a37598..33c75c9 100644
> --- a/drivers/pci/host/pci-hyperv.c
> +++ b/drivers/pci/host/pci-hyperv.c
> @@ -1198,9 +1198,11 @@ static int create_root_hv_pci_bus(struct
> hv_pcibus_device *hbus)
>         hbus->pci_bus->msi = &hbus->msi_chip;
>         hbus->pci_bus->msi->dev = &hbus->hdev->device;
> 
> +       pci_lock_rescan_remove();
>         pci_scan_child_bus(hbus->pci_bus);
>         pci_bus_assign_resources(hbus->pci_bus);
>         pci_bus_add_devices(hbus->pci_bus);
> +       pci_unlock_rescan_remove();
>         hbus->state = hv_pcibus_installed;
>         return 0;
>  }
> @@ -1590,8 +1592,10 @@ static void hv_eject_device_work(struct
> work_struct *work)
>         pdev = pci_get_domain_bus_and_slot(hpdev->hbus->sysdata.domain,
> 0,
>                                            wslot);
>         if (pdev) {
> +               pci_lock_rescan_remove();
>                 pci_stop_and_remove_bus_device(pdev);
>                 pci_dev_put(pdev);
> +               pci_unlock_rescan_remove();
>         }
> 
>         memset(&ctxt, 0, sizeof(ctxt));
> --
> 1.8.5.6