[PATCH 2/2 v2] pci-hyperv: lock pci bus on device eject

[Long Li]

From: Long Li <lon...@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 <de...@microsoft.com> for pointing out the race condition in 
create_root_hv_pci_bus().

Signed-off-by: Long Li <lon...@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