PCI: hv: Lock PCI bus on device eject

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 potentially
modify the bus from multiple places.

Properly lock the bus access.

Thanks Dexuan Cui <decui@microsoft.com> for pointing out the race condition
in create_root_hv_pci_bus().

Reported-by: Xiaofeng Wang <xiaofwan@redhat.com>
Signed-off-by: Long Li <longli@microsoft.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: K. Y. Srinivasan <kys@microsoft.com>

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index 39fafda4deff261de9ed934b997fabceb748fcd1..a1b3c1957d437734ea728d5bd0481a622ec85dae 100644 (file)
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -1209,9 +1209,11 @@ 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;
 }
@@ -1612,8 +1614,10 @@ 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();
        }
 
        spin_lock_irqsave(&hpdev->hbus->device_list_lock, flags);